Vector Control Drives MASTERDRIVES 6SE70 VC

I. SCOPE
This specification covers the requested Vector Control drive(s) design, operating, performance, testing, and support requirements as supplied by the vendor.

II. STANDARDS & CODES
Vector Control drive shall meet or exceed the following:
Environmental class:
3K3 & 3C2 per DIN IEC 721-3-3
Insulation:
DIN VDE 0110, Part 1 (Moisture and condensation are not permissible)
Overvoltage class:
Category III per DIN VDE 0110, Part 2
Overvoltage strength:
Class 1 per DIN VDE 0160
Degree of Protection:
DIN VDE 0470, Part 1 (EN 60 529) standard: IP00, option: IP20
Class of protection:
Class 1 to DIN VDE 0106, Part 1
Shock protection:
DIN VDE 0106 Part 100 (VBG4) and EN 60204-1
RFI level:
To EN 61800-3
Standard: No RFI suppression
Options: Class A1, Class B1 on request; DIN VDE 0875, Part
UL/CSA/CE:
All VFD’s shall carry the UL/CSA/CE labels for the entire power range.

Mechanical specs:
DIN IEC 68-2-6
For stationary applications:
Constant amplitude
- deflection: 0.075 mm in the frequency
range 10 to 58 HZ.
- acceleration: 9.8 ms2 (1xg) in the
frequency range > 58 to 500 Hz.
During transport
- deflection: 3.5 mm in the frequency range
of 5 to 9 Hz.
- acceleration: 9.8 ms2 (1xg) in the
frequency range > 9 to 500 Hz.

III. DOCUMENTATION
Vector Control drive manufacturer shall supply installation instructions, and operation manuals associated with the sold drive equipment. The documentation shall be enclosed and shipped with the drive. Documentation CD DRMS-02051.
Adjustable frequency drive manufacturer must provide start-up and maintenance software free of charge. Contained on Documentation CD DRMS-02051

IV. OPERATING REQUIREMENTS
A. The Vector Control drive shall be capable of operating in the following voltage classifications:
- 230 +/- 15%
- 380 to 460 +/- 15%
- 500 to 575 +/- 15%
- 660 to 690 +/- 15%
Frequency input must accept a 50/60Hz input with a tolerance of +/- 6%.
B. The drive shall have an overload rating of 1.5 times rated current for 60 Seconds.

C. The drive shall control the speed of a NEMA design B, premium efficiency motor, as standard or classes of motor are possible.
D. The drive shall be able to function in anenvironment, without de-rating, with values no higher than 104°F (40°C). The drive shall be able to function, without de-rating, up to an altitude of 3300ft(1000m) above sea level. The relative humidity shall not be higher than 95% (non-condensing).
E. All inverter sections shall be of the PWM (pulse width modulated) type and consist of IGBT inverter bridge through entire power range (GTO or BJT devices not acceptable). Space vector modulation shall be utilized (six step modulation not acceptable). IGBT carrier frequency shall be adjustable for fixed frequency, and have the possibility for random sweep.
F. The drive shall operate with a minimum of 0.98 primary power factor and efficiency rating of 0.96 to 0.98.

V. FUNCTIONAL REQUIREMENTS
Variable frequency drive must provide the following minimum functionality as standard:
• Microprocessor based adjustable frequency drive with sinusoidal PWM current control
• One hardware platform to provide:
V/Hz control with feedback
V/Hz control without feedback
Textile Mode
Open Loop Vector Control
Closed Loop Vector Control
Torque Control
• One control platform to accommodate 1 -5000Horsepower
• IGBT inverter bridge through entire power range.
• Self-tuning (measurement of motor resistance and speed loop optimization)
• .001 Hz setpoint resolution.
• Automatic voltage adjustment within the power range.
• 4 complete motor and setpoint parameter sets.
• Packaging capability to be ordered for common DC bus configurations. Nonregenerative or fully regenerative converter sections available as standard option.

• Ability to operate single or multiple motors with one drive (induction or synchronous motors)
• Flying restart (forward and reverse)
• Frequency avoidance
• Kinetic buffering with power dip ride-thru.
• Dual port RAM for efficient integration of option cards.
• Flash E2Prom on control board
• Two analog inputs (+/- 10VDC or 4-20 mA)
• Two analog outputs (+/- 10VDC or 4-20 mA)
• 4 programmable binary inputs or outputs
• 3 dedicated binary control inputs (24 VDC Control)
• 2 separately addressable serial interface ports: 1 for RS485 and 1 for RS232/485
• User digital interface panel with 4 digit, 7 segment LED display. Stop, start, parameter, speed control, and
forward/reverse.
• Over 100 Warning and Fault messages for comprehensive protection.
• Faults are shown on the digital operator panel (PMU).
• Control Source (START/STOP/Forward&Reverse/Quick Stop) at the following locations:
- PMU (Keypad)
- Terminal Block Inputs
- Serial Port
- OP1S (Optional Keypad with parameter storage memory)
- Simovis (Commissioning software)
• Frequency Reference Source Locations
- PMU (Keypad)
- Terminal Block Inputs
- Digital Operator (Motor Potentiometer)
- Analog Inputs
- Serial Port
- OP1S (Optional Keypad)
- Technology Regulator (PID Functionality) Adjustments
• “Key coded” controlled access authorization to the individual parameters.
• Selectable motor operating mode
• Minimum Frequency adjustment
• Maximum Frequency adjustment
• Constant Voltage Frequency adjustment
• Operating Source (Local, Remote, Serial)
• Voltage Boost/ Current Boost adjustment capabilities
• Motor Overload adjustment
• Overload Time
• Analog Scaling
• Acceleration Time
• Deceleration Time
• Ramp Rounding
• 4 Independently Adjustable Preset Speeds
• Adjustable Carrier Frequency
• Adjustable proportional Gain of Frequency/Speed Regulator
• Adjustable Integration Time of Frequency/Speed Regulator
• Individual adjustment of torque and current limits.
• Self-tuning
• DC Link Regulator
• Space vector regulator method for IGBT’s
• Band Stop Filter
• Dancer Control
• Tension Control
• Pressure/flow control
• Higher level PID
• Open/closed loop control blocks
• Arithmetic Functions (Boolean Logic)
• Braking Control Protection (minimum)
• DC Link Undervoltage Protection
• DC Link Overvoltage Protection
• Heat Sink Overtemperature Protection
• Inverter Overload Protection
• Inverter Overcurrent Protection
• Ground Fault Protection
• Motor Pullout Protection
• Ground Fault Check during start-up
• DC Link Limiter
• RAM/EPROM/EEPROM Malfunction Standard Displays (Selectable)
• Frequency (Hz.)
• Motor Speed
• Output Frequency
• Speed Difference
• Output Current
• DC Link Voltage
• Output Power
• Motor Torque
• Motor Utilization
• Drive Utilization
• Drive operating Hours
• Output Voltage
• Can select any display parameter to be output via terminals for analog output.

Diagnostic Capability
VFD shall posses as standard the capability of recording events simulating an 8 channel oscilloscope. Items to be measured will be selectable with pre-trigger capability and variable length of time measurement.

VI. Optional Configurations
The VFD shall have the following possibilities for additional package and functional options. 

Common DC Bus 

VFD shall have capability of being purchased as a complete package (AC to AC) or as individual units (AC to DC and DC to AC).
Rectifier section (AC to DC): 

 Rectifier section shall be available as regenerative or nonregenerative units. Rectifier sections shall be designed to allow for multiple units in parallel to increase output and 12 pulse designs or active front end unit. Rectifier sections shall be responsible for pre-charge of the DC link capacitors in the inverter sections. Regenerative Rectifiers shall have the capability to reduce DC bus potential. No third party device for regeneration is acceptable.
Inverter section (DC to AC): 

Inverter shall have complete control and diagnostic capabilities. DC link capacitors shall be located in each inverter section.

Optional Feedback Boards
• SBP- Sensor Board Pulse: feedback card for pulse encoders
• DTI – Digital Tach Interface for isolation of long length encoder leads.
• ATI – Analog Tach Interface Optional Communication Boards
• CBP- Communication Board Profibus: Profibus communication card (12 Mbaud)
• CBP2-Communication Board Profibus MC (12 Mbaud with peer to peer functionality)
• CBD- Communication Board DeviceNet: DeviceNet Protocol Communication Card
• CBC- Communication Board Can: CAN Protocol Communication Card
• SCB1- Serial Communication Board 1: for additional I/O, in conjunction with SCI1 or SCI2, or peer to peer communications - Fiber-optic
• SCI2- Serial Communication Board 2: for additional RS485 communication port or peer to peer communication –Copper
• SLB- SimoLink Board: high speed fiberoptic peer to peer network 11Mb(used for synchronization & peer to peer)

Optional I/O Expansion Boards
• EB1- Expansion Board 1: additional Binary and Analog I/O (Copper)
• EB2- Expansion Board 2: additional Binary and Analog I/O with Relay Logic (Copper)
• SCB1- Serial Communication Interface 1: for additional DIN Rail Mounted I/O. Used in conjunction, by fiber optic link, with the SCB1
• SCB2- Serial Communication Interface 2: for additional DIN Rail Mounted I/O. Used in conjunction, by fiber optic link, with the SCB1 board
• 120 Volt Digital Signal Interface, adapter card for accepting 120 Volt based signaling direct. 

Optional Technology Boards
T100 - Dancer control
Tension control
Pressure/flow control
Arithmetic functions (Boolean Logic)
Higher level PID
USS-Bus
Peer-to-Peer
Open/closed loop control blocks
5 Analog Inputs
2 Analog Outputs
8 Binary Inputs
5 Binary Outputs
T300 - Parameterizable function blocks
Sectional
Winders
Position control (Linear &
Angular)
Pulse encoder input (nonfloating)
USS-Bus
Peer-to-Peer
7 Analog inputs
4 Analog outputs
16 Binary inputs
8 Binary outputs
T400 - Parameterizable function blocks,
or Configurable with CFC editor.
Sectional
Winders
Flying Shear / Sheet Cutter
Position control (Linear & Angular)
Pulse encoder input (nonfloating)
USS-Bus
Peer-to-Peer
5 Analog inputs
2 Analog outputs
8 Binary inputs
2 Binary outputs
4 bi-directional binary inputs or outputs

Using Switching Devices to Develop AC Output

In the following example, one phase of a three-phase output is
Output used to show how an AC voltage can be developed. Switches
replace the IGBTs. A voltage that alternates between positive
and negative is developed by opening and closing switches in
a specific sequence. For example, during steps one and two
A+ and B- are closed. The output voltage between A and B is
positive. During step three A+ and B+ are closed. The difference
of potential from A to B is zero. The output voltage is zero.
During step four A- and B+ are closed. The output voltage from
A to B is negative. The voltage is dependent on the value of the
DC voltage and the frequency is dependent on the speed of the
switching. An AC sine wave has been added to the output (A-B)
to show how AC is simulated.

IGBTs insulated gate bipolar transistor

IGBTs (insulated gate bipolar transistor) provide a high
switching speed necessary for PWM inverter operation. IGBTs
are capable of switching on and off several thousand times a
second. An IGBT can turn on in less than 400 nanoseconds
and off in approximately 500 nanoseconds. An IGBT consists
of a gate, collector and an emitter. When a positive voltage
(typically +15 VDC) is applied to the gate the IGBT will turn on.
This is similar to closing a switch. Current will flow between
the collector and emitter. An IGBT is turned off by removing the
positive voltage from the gate. During the off state the IGBT
gate voltage is normally held at a small negative voltage (-15
VDC) to prevent the device from turning on.

Control Logic and Inverter

Output voltage and frequency to the motor are controlled by the
control logic and inverter section. The inverter section consists
of six switching devices. Various devices can be used such
as thyristors, bipolar transistors, MOSFETS and IGBTs. The
following schematic shows an inverter that utilizes IGBTs. The
control logic uses a microprocessor to switch the IGBTs on and
off providing a variable voltage and frequency to the motor.

Converter and DC Link

The converter section consists of a fixed diode bridge rectifier
which converts the three-phase power supply to a DC voltage.
The L1 choke and C1 capacitor(s) smooth the converted DC
voltage. The rectified DC value is approximately 1.35 times the
line-to-line value of the supply voltage. The rectified DC value is
approximately 650 VDC for a 480 VAC supply.

Pulse Width Modulation

Pulse width modulation (PWM) drives, like the Siemens
MICROMASTER and MASTERDRIVE VC, provide a more
sinusoidal current output to control frequency and voltage
supplied to an AC motor. PWM drives are more efficient and
typically provide higher levels of performance. A basic PWM
drive consists of a converter, DC link, control logic, and an
inverter.

Current Source Inverter (CSI)

The current source inverter (CSI) uses an SCR input to produce
a variable voltage DC link. The inverter section also uses SCRs
for switching the output to the motor. The current source
inverter controls the current in the motor. The motor must be
carefully matched to the drive.

Variable Voltage Inverter (VVI)

The variable voltage inverter (VVI) uses an SCR converter
bridge to convert the incoming AC voltage into DC. The SCRs
provide a means of controlling the value of the rectified DC
voltage from 0 to approximately 600 VDC. The L1 choke and
C1 capacitor(s) make up the DC link section and smooth
the converted DC voltage. The inverter section consists of
six switching devices. Various devices can be used such as
thyristors, bipolar transistors, MOSFETS, and IGBTs. The
following schematic shows an inverter that utilizes bipolar
transistors. Control logic (not shown) uses a microprocessor
to switch the transistors on and off providing a variable voltage
and frequency to the motor.

Variable Voltage Inverter

This type of switching is often referred to as six-step because
it takes six 60° steps to complete one 360° cycle. Although the
motor prefers a smooth sine wave, a six-step output can be
satisfactorily used. The main disadvantage is torque pulsation
which occurs each time a switching device, such as a bipolar
transistor, is switched. The pulsations can be noticeable at low
speeds as speed variations in the motor. These speed variations
are sometimes referred to as cogging. The non-sinusoidal
current waveform causes extra heating in the motor requiring a
motor derating.

Basic AC Drives

AC drives, inverters, and adjustable frequency drives are all
terms that are used to refer to equipment designed to control
the speed of an AC motor. The term SIMOVERT is used by
Siemens to identify a SIemens MOtor inVERTer (AC drive).
AC drives receive AC power and convert it to an adjustable
frequency, adjustable voltage output for controlling motor
operation. A typical inverter receives 480 VAC, three-phase,
60 Hz input power and in turn provides the proper voltage and
frequency for a given speed to the motor. The three common
inverter types are the variable voltage inverter (VVI), current
source inverter (CSI), and pulse width modulation (PWM).
Another type of AC drive is a cycloconverter. These are
commonly used for very large motors and will not be described
in this course. All AC drives convert AC to DC, and then through
various switching techniques invert the DC into a variable
voltage, variable frequency output.

Z Axis in drive

The axis of motion that is always parallel to the
principle spindle of the machine.

Y Axis in ac/dc drive

The axis of motion that is perpendicular to both
the X and Z axes.

X Axis in ac/dc drive

The axis of motion that is always horizontal and
parallel to the work holding surface.

Wye Voltage System

This provides all three phases of current carried
by three “hot” wires and one neutral wire.
Sometimes it is called a 3 phase 4 wire system.
The wye voltage system is the most commonly
used three phase voltage system.

Wye Connection

A standard three-wire transformer connection
with similar ends of the single-phase coils
connected. This common point forms the
electrical neutral point and may be grounded.

Work - A force moving an object over a distance

A force moving an object over a distance.
Measured in inch-ounces (in-oz) or foot-pounds
(ft-lbs). Work = Force X Distance.

Withstand Rating (circuit breakers)

This is the level of RMS symmetrical current
that a circuit breaker can carry with the contacts
in the closed position for a maximum of 30
cycles, typically.

Wireway

Sheet metal troughs with hinged or removable
covers for housing and protecting electric wires
and cable and in which conductors are laid in
place after the wireway has been installed.

Winding Loss (transformers)

The losses, principally I2R loss in the winding of
the transformer, expressed in watts or KW.
Winding losses vary with the square of the load.

Watthour Meter

Meter mounted on the outside of a house and
attached to service drop conductors. This meter
measures the amount of electricity used in the
house.

Watertight

"Watertight" means that a device is so constructed as to exclude water applied in the form of a hose stream, under specified test conditions.

Wall Duct

A steel-enclosed wall or ceiling lay-in duct
system (raceway). Wall duct is UL listed for
enclosure of wiring for medical diagnostic
equipment.

VVI

A type of AC adjustable frequency drive that
controls the voltage and frequency to the motor
to produce variable speed operation. A VVI type
drive controls the voltage in a section other than
the output section where frequency generation
takes place. The frequency control is
accomplished by an output bridge circuit which
switches the variable voltage to the motor at the
desired frequency.

VPI Vacuum Pressure Impregnation

Vacuum Pressure Impregnation. A
manufacturing process whereby the coils of a
transformer are impregnated with varnish, resin
or other process fluid by use of both a vacuum
and pressure cycle.

Voltage Regulation (power conditioning)

This is a measurement of a voltage stabilizers
ability to hold its output close to the nominal
rating despite a fluctuating input. This is
normally expressed as a +/- percentage.

Voltage Regulation

The voltage drop that will occur in the
transformer under full load as a percentage of
the open circuit voltage rating of the winding.
Varies with load and power-factor of the load-
.1% to 10% might be outside limits of normal
range.

Voltage Boost

Increasing the Volts/Hertz ratio of drives at low
speeds to compensate for resistance losses in
the motor core. This compensation allows the
motor to develop rated torque at low speeds.

Voltage (represented as an “E”)

The force or “push” needed to move the
electrons. Voltage can also be thought of as the
difference of force or potential between two
points. Voltage is measured in volts.

Vector

A quantity that has magnitude, direction and
sense. This quantity is commonly represented
by a directed line segment whose length
represents the magnitude and whose orientation
in space represents the direction.

Variable Volts/Hertz

When the output volts varies at a different rate
than the rate at which the output frequency
varies. Variable Volts/Hertz is sometimes
desired to decrease motor noise and reduce
motor core losses.

UL Underwriters Laboratories

Underwriters Laboratories. This is a non-profit
corporation that establishes safety and
performance standards for electrical products
and lists products that meet these standards.
Manufacturers who want UL listing make
application to UL to list their products. These
products are evaluated by a highly-trained
technical staff who uses state of the art
equipment to determine whether products
comply with UL standards. UL also has a
network of inspectors who make periodic and
unannounced visits to factories. There they
check compliance with UL standards in the
production of electrical equipment that bears the
UL label.

Under voltage

A fault condition that occurs when the input
voltage to the drive is below the trip value.
Undervoltage is not a parameter that can be
adjusted.

Underfloor Duct

A concrete encased single compartment or
multi-compartment duct system providing
distribution and access to power and
telecommunications wiring.

Turbines

Machines which drive generators. Turbines are
powered by various sources of energy, such as
water, coal or nuclear energy.

Trench Duct

A flush floor wire management system.

Transverse Mode Noise (power conditioning)

This is electrical interference that occurs
between hot and neutral.

Transmission Networks

Method by which power plants deliver generated
electricity to their customers. Utility companies
transmit electrical power at high voltage levels,
sometimes as high as 750,000 volts (750kV)
because it is less expensive. Power transmitted
at high voltage has lower current, and lower
current permits the use of a smaller conductor
or wire. Operating voltages used in resident,
commercial and industrial settings are between
120 volts and 600 volts.

Transmission lines

Transmission lines carry, or transmit, electricity
to homes and businesses.

Transistor

A solid state three-terminal device that allows amplification of signals and can be used for switching and control. The three terminals are called the emitter, base and collector.

Transformer Regulation

The percentage difference between voltage at
the secondary terminals under no-load condition
versus voltage under full-load. This value
depends on the load power factor and is usually
reported at 1.0 PF and 0.8 PF.

Transformers

The purpose of a transformer is to change the
voltage from one level to another. A transformer
is composed of three parts: a coil, the primary
winding and the secondary winding. “Windings”
consist of coils of wire wrapped around the core
(which can be made out of iron or metal). If an
electrical current is passed through a wire
wrapped around a piece of iron/metal, the
iron/metal will become magnetized. A magnetic
field is created. This illustrates the
electromagnetic principle. In a transformer, the
electromagnetic principle works as follows:
power is fed into the primary winding. The
electrical current being fed into the primary
winding is transformed into magnetic energy.
The core then carries the magnetic energy to
the secondary winding. Working in reverse, the
secondary winding transforms the magnetic
energy back into electrical energy. It is the turns
in the transformer that give specific primary and
secondary voltages.

Transfer Time (UPS)

The time it takes for a UPS to “Cut over” from
utility power to battery power.

Transducer

A device that converts one energy form to
another (e.g., mechanical to electrical). Also a
device that when actuated by signals from one
or more systems or media, can supply related
signals to one or more other systems or media.

Totally Enclosed Machine (Motor)

A totally enclosed machine is one so enclosed
as to prevent the free exchange of air between
the inside and the outside of the case. It is not
sufficiently enclosed to be termed air-tight.
A. Totally Enclosed Fan-Cooled is a totally
enclosed machine equipped for exterior
cooling by means of a fan or fans integral
with the machine but external to the
enclosing parts.
B. Explosionproof Machine is a totally enclosed
machine whose enclosure is designed and
constructed to withstand an explosion of a
specified gas or vapor which may occur
within it and to prevent the ignition of the
specified gas or vapor surrounding the
machine by sparks, flashes, or explosions of
the specified gas or vapor which may occur
within the machine casing.
C. Dust-Ignition-Proof Machine is a totally
enclosed machine whose enclosure is
designed and constructed in a manner which
will exclude ignitable amounts of dust or
amounts which might affect performance or
rating, and which will not permit arcs, sparks
or heat otherwise generated or liberated
inside of the enclosure to cause ignition of
exterior accumulations or atmospheric
suspensions of a specific dust on or in the
vicinity of the enclosure.
D. Waterproof Machine is a totally enclosed
machine so constructed that it will exclude
water applied in the form of a stream from a
hose, except that leakage may occur around
the shaft provided it is prevented from
entering the oil reservoir and provision is
made for automatically draining the machine.
The means for automatic draining may be a
check valve or a tapped hole at the lowest
part of the frame which will serve for
application of a drain pipe.
E. Totally Enclosed Water-Cooled Machine is a
totally enclosed machine which is cooled by
circulating water, the water or water
conductors coming in direct contact with the
machine parts.
F. Totally Enclosed Water-Air-Cooled Machine
is a totally enclosed machine which is cooled
by circulating air which, in turn, is cooled by
circulating water. It is provided with a watercooled
heat exchanger for cooling the interior
air and a fan or fans, integral with the rotor
shaft or separate, for circulating the internal
air.
G. Totally Enclosed Air-to-Air Cooled Machine is
a totally enclosed machine which is cooled
by circulating the internal air through a heat
exchanger which, in turn, is cooled by
circulating external air. It is provided with an
air to air heat exchanger for cooling the
internal air and a fan or fans, integral with the
rotor or separate, for circulating the internal
air and a separate fan for circulating the
external air.
H. Totally Enclosed Fan-Cooled Guarded
Machine is a totally enclosed fan-cooled
machine in which all openings giving direct
access to the fan are limited in size by the
design of the structural parts or by screens,
grilles, expanded metal, etc., to prevent
accidental contact with the fan. Such
openings shall not permit the passage of a
cylindrical rod 0.75 inch in diameter, and a
probe shall not contact the blades, spokes or
other irregular surfaces of the fan.
I. Totally enclosed Air-Over Machine is a totally
enclosed machine intended for exterior
cooling by a ventilating means external to the
machine.

Torque Control

A method of using current limiting circuitry to
regulate torque instead of speed.

Torque Constant

(in-lbs) This motor parameter provides a
relationship between input current and output
torque. For each ampere of current applied to
the rotor, a fixed amount of torque will result.

Torque (motor)

A turning force applied to a shaft, tending to
cause rotation. Torque is normally measured in
ounce-inches or pound-feet and is equal to the
force applied, times the radius through which it
acts

Tight

"Tight" means that an enclosure is so
constructed that it will exclude the specified
material under specified conditions.

Throat

Extension of the cabinet or enclosure that
surrounds bushings or cable connections. Used
for joining a transformer to adjacent switchgear,
busway, etc. Usually rectangular and fitted with
a flange for bolting to the connected gear.

Three Phase Voltage System

Provides three “hot” wires for the customer’s
use. The three phase voltage system has two
configurations, wye and delta.

Thread Speed

A fixed low speed, usually adjustable, supplied to provide a convenient method for loading and threading machines. May also be called a preset speed.

Tap (transformers)

Connection brought out of a winding at some
point between its extremities, usually to permit
changing the voltage or current ratio.

Tachometer-Generator (Tach)

A small generator normally used as a rotational
speed sensing device. Tachometers are
typically coupled to the shaft of DC or AC
motors requiring close speed regulation. The
tach feeds a signal to a controller which then
adjusts the output voltage or frequency to the
motor.

Synchronous Speed

The speed of an AC induction motor’s rotating
magnetic field. It is determined by the frequency
applied to the stator and the number of
magnetic poles present in each phase of the
stator windings. Mathematically, it is expressed
as:
Sync Speed (RPM) = 120 X Applied Freq.
(Hz)/Number of poles per phase.

Surge Protection

The process of absorbing and clipping voltage
transients on an incoming AC line or control
circuit. MOVs (Metal Oxide Varistors) and
specially designed R-C networks are usually
used to accomplish this.

Steppedwave (UPS)

This waveform combines the benefits of a
sinewave with the cost advantages of a
squarewave device. This is acceptable to the
majority of electronic loads.

Stator (motor)

A stationary iron core with wire windings. The
stator is attached to the case.

Stability

The ability of a drive to operate a motor at
constant speed (under varying load), without
“hunting” (alternatively speeding up and slowing
down). It is related to both the characteristics of
the load being driven and electrical time
constants in the drive regulator circuits.

Squirrel Cage AC Motor

Most commonly used motor in industry and in
the home.

Squarewave (UPS)

This is a poor manifestation of a sinewave. This
is found on economy models of UPS. This may
not be beneficial to most electronic loads.

Split Bus Panelboard

A panelboard with two or three sets of isolated
bus bars mounted in the same interior.

Speed Regulation

The numerical measure in percent, of how
accurately the motor speed can be maintained.
It is the percentage of change in speed between
full load and no load.

Speed Range

The speed minimum and maximum at which a
motor must operate under constant or variable
torque load conditions. A 50:1 speed range for a
motor with top speed of 1800 RPM means the
motor must operate as low as 36 RPM and still
remain within regulation specifications.
Controllers are capable of wider controllable
speed ranges than motors because there is no
thermal limitation, only electrical. Controllable
speed range of a motor is limited by the ability
to deliver 100% torque below base speed
without additional cooling.

Slip Compensation

Method of increasing the output frequency to
maintain motor speed as the load on the motor
increases

Slip

The difference between rotating magnetic field
speed (synchronous speed) and rotor speed of
AC induction motors. Usually expressed as a
percentage of synchronous speed.

Slewing

Slewing is an incremental motion of the motor
shaft or machine table from one position to
another at maximum speed without losing
position control.

Sleetproof

"Sleetproof" means that a device is so
constructed or protected that the accumulation
of sleet (ice), under specified conditions, will not
interfere with the successful operation of the
apparatus, including the external operating
mechanism.

Sleet Resistant

"Sleet Resistant" means that an apparatus is so
constructed that accumulation and melting of
sleet (ice), under specified conditions, will not
damage the apparatus.

Skewing

Refers to time delay or offset between any two
signals in relation to each other.

Skew

The arrangement of laminations on a rotor or
armature to provide a slight angular pattern of
their slots with respect to the shaft axis. This
pattern helps to eliminate low speed cogging in
an armature and minimize induced vibration in a
rotor as well as reduce associated noise.

Single phase voltage system

A single phase voltage system can supply 120
volts or 240 volts. The system uses three wires,
two “hot” (carrying current) and one neutral wire

Sinewave (UPS)

This describes the shape of the output wave
from the inverter. A sinewave is the same shape
as that supplied from the utility.

Silicon Controlled Rectifier

(SCR) A solid state switch, sometimes referred
to as a thyristor. The SCR has an anode,
cathode and control element called a gate.
SCR’s are turned on by a voltage pulse applied
between the gate and cathode. They are turned
off when the current between the cathode and
anode reaches zero. The device provides
controlled rectification since it can be turned on
at will. The SCR can rapidly switch large
currents at high voltages. They are small in size
and low in weight.

Shock Load

The load seen by a clutch, brake or motor in a
system which transmits high peak loads. This
type of load is present in crushers, separators,
grinders, conveyors, winches, and cranes

Short Circuit Current Ratings (SCCR)

SCCR are used to select end-use equipment for
specific available fault current applications. This
maximum current rating applies only to end-use
equipment such as switchboards, panelboards
and motor control centers. The SCCR covers
not only the overcurrent protective device in the
end-use equipment, but also the overall
construction of the equipment i.e. it is an
integrated equipment rating.

Shipping Splits (motor control centers)

Motor Control Centers are shipped in more than
one container to ease in handling.

Shaft (motor)

A metal rod mounted in the case using bearing
assemblies that allow the shaft to turn (rotate).

Service Fittings

Sometimes known as "activation units" access the duct system to provide power, computer access, and telecommunications services in an existing facility.

Service Factor (motor)

This defines a margin of safety that allows for
those times when motors might be operated
above their rated horsepower. This service
factor protects the motor against damage that
might be caused by the occasional excessive
load.
When used on a motor nameplate, a number
which indicates how much above the nameplate
rating a motor can be loaded without causing
serious degradation (i.e., a motor with 1.5 S-F
can produce 15% greater torque than one with
1.0 S-F.) When used in applying motors or
gearmotors, it is a figure of merit which is used
to adjust measured loads in an attempt to
compensate for conditions which are difficult to
measure or define.

Service Entrance Conductors

Conductors which are extended from the watthour
meter to the house.

Service Entrance

The place where the electric supply from the
utility company enters a building.

Service Drop Conductors

Electrical wires from the power lines which
attach to a house.

Series Connected System

A system consisting of a combination of two
overcurrent protective devices connected in
series. The lineside (main) device must have an
interrupting rating equal to or greater than the
available fault current at the lineside terminals
of the device. The loadside (branch) breaker
has a lower interrupting rating. The series rated
combinations are based on actual UL testing.

Sensors (motor control)

Devices which are activated when they detect
conditions such as the presence of a metal, the
pressure of a liquid or gas, or the position of an
object.

Rotor (motor)

A rotating iron core with wire windings. The rotor
is attached to the shaft.

RMS Root Mean Square

Root Mean Square

Reversing

Changing direction of rotation of the motor
armature or rotor. A DC motor is reversed by
changing the polarity of the field or the
armature, but not both. An AC motor is reversed
by reversing the connections of one leg on the
three phase power line. The reversing function
can be performed in one of the following ways:
A. (DC) Contactor Reversing is done by
changing the phase rotation of an AC motor
or the polarity to a DC motor armature with
switching contactors. The contactors are
operated by momentary push buttons, and/or
limit switches to stop the motor and change
directions. A zero speed (anti-plugging)
circuit is associated with this system to
protect the motor and control.
B. (DC) Field Reversing is accomplished by
changing the DC polarity to the motor shunt
field. This type of reversing can be
accomplished with DC rated contactors or by
means of an electrically controlled solid state
field supply.
C. (DC) Manual Reversing is the act of
reversing the DC polarity to the motor
armature by changing the position of a single
switch. The switch is usually detented to give
a degree of mechanical anti-plugging
protection. Limit switches and remote
stations cannot be used with this system.
Dynamic braking is recommended.
D. (AC or DC) Static Reversing is the act of
reversing the DC polarity of the DC motor
armature or phase rotation of an AC motor
with no mechanical switching. This is
accomplished electronically with solid state
devices. Solid state anti-plugging circuitry is
generally a part of the design.

Resolution

The smallest distinguishable increment into
which a quantity can be divided (e.g. position or
shaft speed). It is also the degree to which
nearly equal values of a quantity can be
discriminated. For encoders, it is the number of
unique electrically identified positions occurring
in 360 degrees of input shaft rotation.

Resistant (Used as suffix)

"Resistant" means that a device is constructed,
protected, or treated so that it will not be
damaged when subjected to the specified
material or conditions for a specified period of
time. Such as "sleet resistant."

Resistance (represented as an “R”):

This is the property that prevents electrons from
moving. Sometimes it is referred to as a “load”.
Resistance is measured in ohms.

Relay Section (motor control centers)

Includes a full height, full width removable panel
with a 72" hinged door to provide space for
customer devices in a Motor Control Center.

Regulation

The ability of a control system to hold a speed
once it has been set. Regulation is given in
percentages of either base speed or set speed.
Regulation is rated upon two separate sets of
conditions:
A. Load Regulation (speed regulating) is the
percentage of speed change with a defined
change in load, assuming all other
parameters to be constant. Speed regulation
values of 2% are possible in drives utilizing
armature voltage feedback, while regulation
of 0.01% is possible using digital regulator
schemes.
B. Line Regulation is the percentage of speed
change with a given line voltage change,
assuming all other parameters to be
constant.

Regenerative Control

A regenerative drive contains the inherent
capability and/or power semi-conductors to
control the flow of power to and from the motor.

Regenerative Braking

The technique of slowing or stopping a drive by
regeneration. See also Braking.

Regeneration

A characteristic of a motor to act as a generator
when the CEMF is larger than the drive’s
applied voltage (DC drives) or when the rotor
synchronous frequency is greater than the
applied frequency (AC drives).

Rectifier

A device that transforms alternating current into
direct current.

Reactance

Any force that opposes changes in current or
voltage. The inertia of electrons causes them to
oppose sudden changes in current flow or
voltage.

Raintight

"Raintight" means that a device is so
constructed or protected as to exclude rain
under specified test conditions.

Rain proof

"Rainproof" means an apparatus is so
constructed, protected, or treated as to prevent
rain, under specified test conditions, from
interfering with successful operation of the
apparatus.

Radial Feed

Incoming HV cables end at this transformer in a
single set of HV bushings.

Pulse Width Modulation (PWM)

A type of AC adjustable frequency drive that
accomplishes frequency and voltage control at
the output section (inverter) of the drive. The
drive’s output voltage is always a constant
amplitude and by “chopping” (pulse width
modulating) the average voltage is controlled.

Push buttons (motor control)

Devices which are activated manually by a
person.

Pull-Up Torque

The torque required to accelerate the load from
standstill to full speed (where breakdown torque
occurs), expressed in percent of running torque.
It is the torque required not only to overcome
friction, windage and product loading but also to
overcome the inertia of the machine. The torque
required by a machine may not be constant
after the machine has started to turn. This load
type is characteristic of fans, centrifugal pumps
and certain machine tools.

Pull-Out Torque

(Synchronous Motors) The maximum running
torque of a synchronous motor.

Pull-In Torque

(Synchronous Motors) The maximum constant
torque which a synchronous motor will
accelerate into synchronism at rated voltage
and frequency.

Proof

"Proof" means a device is constructed,
protected, or treated so that successful
operation of the apparatus is not interfered with
when subjected to the specified material or
condition. Such as "rainproof."

Preset Speed

Preset speed refers to one or more fixed speeds
at which the drive will operate.

Power factor

The ratio of active power to total power. Power
factor can be expressed as percentage or as a
raw number. For example, .80 or 80%. If active
power equals total power, the power factor of
the load would be 1 or 2 or 100%. This is the
highest power factor possible.

Power

Work done per unit of time. Measured in HP or watts: 1 HP = 33,000 ft-lb/min = 746 watts

Positive Feedback

Positive feedback is a condition where the
feedback is additive to the input signal.

Position Transducer

An electronic device (e.g. encoder or resolver)
that measures actual position and converts this
measurement into a feedback signal convenient
for transmission. This signal may then be used
as an input to a programmable logic controller
which controls the parameters of the positioning
system.

Poke Thru Fittings

A flexible and inexpensive method of providing
power receptacles, computer access, and
telecommunications services in an existing
facility.

Plugging

Plugging refers to a type of motor braking
provided by reversing either line voltage polarity
or phase sequence so that the motor develops a
counter-torque which exerts a retarding force to
brake the motor.

Phase (Æ, or PH)

One of three streams of current which is
produced by a generator. Each phase of current
flows from a generator in a separate conductor.

Panel boards

A single panel or group of panel units designed
for assembly in the form of a single panel;
including buses, automatic overcurrent devices,
and equipped with or without switches for the
control of light, heat, or power circuits; designed
to be placed in a cabinet or cutout box placed in
or against a wall or partition and accessible only
from the front.

Over voltage

Overvoltage is a fault condition that occurs
when the input voltage to the drive exceeds the
trip value. Overvoltage is not a parameter that
can be adjusted.

Overshoot

The amount that a controlled variable exceeds
desired value after a change of input.

Overload Capacity

The ability of the drive to withstand currents
beyond the systems continuous rating. It is
normally specified as a percentage of full load
current for a specified time period. Overload
capacity is defined by NEMA as 150% of rated
full load current for one minute for Standard
Industrial DC Motors.

Overcurrent Condition

Excessive circuit current which could damage
equipment connected to the circuit. Typically a
circuit breaker is designed to sense overcurrent
conditions. When it does the breaker opens the
electrical path protecting the connected
equipment from being damaged by excessive
current. When this happen the circuit breaker is
said to have “tripped”. When the situation that
caused an overcurrent has been corrected,
power can be restored to the circuit. This is
done by moving the circuit breaker handle from
its trip position to the “off” position to reset it.
Then the handle can be moved to the “on”
position.

Overcurrent (circuit breakers)

Any current in excess of the rated current of
equipment or the ampacity of a conductor.

Output Devices

They receive electrical signals from logic
devices. Two examples of output devices are
contactors and starters.

Service Deviation

Defines speed change due to changes in
ambient conditions greater than these typical
variations:
Condition Change
AC Line Voltage ± 10%
AC Line Frequency ± 3%
Ambient Temperature 15° C

Operating Deviation

Defines speed change due to load change and
typically assumes:
1. A change from one steady state load value to
another (not transient).
2. A 95% maximum load change.

Operating/Service Deviation

A means of specifying the speed regulating
performance of a drive controller generally in
percent of base speed.

Open Machine (Motors)

A machine having ventilating openings which
permit passage of external cooling air over and
around the windings of the machine.
A. Dripproof Machine is an open type machine
in which ventilating openings are so
constructed that successful operation is not
interfered with when drops of liquid or solid
particles strike or enter the enclosure at any
angle from 0 to 15 degrees downward from
vertical.
B. Splashproof Machine is an open type
machine in which ventilating openings are so
constructed that successful operation is not
interfered with when drops of liquid or solid
particles strike or enter the enclosure at any
angle not greater than 100 degrees
downward from the vertical.
C. Semiguarded Machine is an open machine in
which part of the ventilating openings in the
machine, normally the top half, are guarded
as in the case of a “guarded machine” but the
others are left open.
D. Guarded Machine (NEMA Standard) is an
open machine in which all openings giving
direct access to live metal or rotating parts
(except smooth rotating surfaces) are limited
in size by the structural parts or by the
screens, baffles, grilles, expanded metal or
other means to prevent accidental contact
with hazardous parts. Openings giving direct
access to such live or rotating parts shall not
permit the passage of a cylindrical rod 0.75
inch in diameter.
E. Dripproof Guarded Machine is a dripproof
machine whose ventilating openings are
guarded in accordance with the definition of
a guarded machine.
F. Open Externally Ventilated Machine is one
which is ventilated by means of a separate
motor driven blower mounted on the machine
enclosure. This machine is sometimes known
as a blower-ventilated or a force-ventilated
machine.
G. Open Pipe Ventilated Machine is basically an
open machine except that openings for
admission of ventilating air are so arranged
that inlet ducts or pipes can be connected to
them. Air may be circulated by means
integral with the machine or by means
external to the machine (separately or forced
ventilated).
H. Weather-Protected Machine is an open
enclosure divided into two types:
1. Type 1 enclosures have ventilating
passages constructed to minimize the
entrance of rain, snow, airborne particles
and prevent passage of a 0.75 inch
diameter cylindrical rod.
2. Type 2 enclosures provide additional
protection through the design of their
intake and exhaust ventilating passages.
The passages are so arranged that wind
and airborne particles blown into the
machine can be discharged without
entering directly into the electrical parts of
the machine. Additional baffling is
provided to minimize the possibility of
moisture or dirt being carried inside the
machine.

OP Amp

An Operational Amplifier is usually a high-gain
DC amplifier that is designed to be used with
external circuit elements.

Open Loop

A control system that lacks feedback.

One Line Diagram

A simplified wiring diagram with a single line
representing all the conductors and symbols
representing the elements of the system.

Oiltight

"Oiltight" means that a device is so constructed
or protected as to exclude oils, coolants, and
similar liquids under specified test conditions.

Oil Resistant Gaskets

Gaskets (used in an enclosure) that are made of
those materials which resist oil or oil fumes.

Offset

The steady state deviation of a controlled
variable from a fixed setpoint.

Noise (power conditioning)

Unwanted electrical signals which produce
undesirable effects in circuits in which they
occur.

NFPA National Fire Protection Association

National Fire Protection Association. This
association has developed a set of minimum
standards for electrical installations in home,
commercial and industrial environments, called
the National Electrical Code (NEC). Although
the NEC is nationally accepted in the industry, it
standards are subject to interpretation by local
authorities. Each town, city, county or state may
establish codes to govern the installation of
electrical equipment or wiring.

NEMA Type A (motor control centers)

NEMA Type A (motor control centers)
User field wiring connects directly to internal
device terminals in the unit and is provided only
on Class 1 Motor Control Centers.
NEMA Type B (motor control centers)
User field control wiring connects directly to the
control unit terminal block(s) in or adjacent to
each unit and user field load wiring connects
directly to the device adjacent to the vertical
wireway.
NEMA Type C (motor control centers)
User field control wiring on all units and load
wiring on Size 3 or smaller units connects
directly to master terminal blocks mounted at
the top and bottom of those vertical sections
containing control units. Control wiring on all
units and load wiring on Size 3 or smaller units
are factory wired to their mater terminal block.
User field load wiring for Size 4 or larger units
connects directly to the device terminals.

NEMA Type 1 Enclosure

NEMA Type 1 Enclosure 

General Purpose. Primarily protects against
accidental contact with enclosed equipment.
Suitable for indoor use.
NEMA Type 12 Enclosure
Indoor Dusttight and Driptight. Without
knockouts. Protects against liquids that are not
corrosive including oil and coolants. Often found
in an industrial environment.
NEMA Type 12K Enclosure
Same as Type 12 but with knockouts in top and
bottom walls only.
NEMA Type 3 Enclosure
Dusttight, Raintight. Protects against dust and
rain. Used outdoors. They are not sleet (ice)
proof. Applications include ship docks, subways,
and tunnels.
NEMA Type 3R Enclosure
Rainproof, Sleet Resistant. Protects the normal
operation of the enclosed equipment from
interference due to rain, and resists equipment
damage due to sleet. For outdoor use in location
affected by rain and/or sleet.
NEMA Type 4 Enclosure
Watertight. Protects against water interfering in
the operation of the enclosed equipment. The
enclosure may be used outdoors or in dairies or
other food preparation environments.
NEMA Type 4X Enclosure
Watertight, Corrosion Resistant. Protection is
similar to NEMA Type 4 except Type 4X
enclosure is constructed of corrosion resistant
material. Used in fertilizer and chemical
manufacturing plants, meat packing plants
where environmental contaminants would
destroy the metal enclosure over time.
NEMA Type 5 Enclosure
Indoor Dusttight. Intended for use indoors to
protect enclosed equipment against fibers and
flyings, lint, dust, and dirt.
NEMA Type 7 Enclosure
Class 1, Group A, B, C and/or D. Indoor
Hazardous Locations. Protects against
explosions caused by electrical arcs that occur
during normal operation of motor control or
switching equipment. The enclosure is
constructed to prevent flammable gases or
vapors from entering the enclosure. Used in oil
refineries and natural gas plants. Do not decide
between NEMA Type 7 or NEMA Type 9 for
your customers. Let them tell you which
enclosure type will meet their requirements.
NEMA Type 9 Enclosure
Similar to NEMA Type 7 except the enclosure
protects against environmental (airborne) dust.
Used in grain elevators and flour milling plants.
Do not decide between NEMA Type 7 or NEMA
Type 9 for your customers. Let them tell you
which enclosure type will meet their
requirements.

NEMA Class 1 (motor control centers)

Independent units consisting of mechanical
groupings of combination motor control units,
feeder taps, and electrical devices arranged for
convenient assembly. Wiring is complete
between components within each unit.
Connections between units are not provided.
NEMA Class 2 (motor control centers)
Interconnected units consisting of mechanical
groupings of combination motor control units,
feeder taps, and electrical devices arranged for
convenient assembly. Electrical interlocking and
wiring between units is provided. These
interconnections are completed as called out by
the purchaser.

Negative Feedback

A condition where feedback is subtractive to the
input reference signal. Negative feedback forms
the basis for automatic control systems.

NEC

The National Electrical Code is
recommendations of the National Fire
Protection Association and is revised every
three years. City or state regulations may differ
from code regulations and take precedence over
NEC rules.

NEMA

National Electrical Manufacturers Association.
The focus of NEMA is to establish voluntary
standards for its members to ensure that the
products they manufacture have general areas
of uniformity. NEMA produces more than 200
standards publications.

Multispeed Motor

An induction motor that can obtain two, three or
four discrete (fixed) speeds by the selection of
various stator winding configurations.

Motor Overload

This is a condition which exists when a motor
load increases above normal. The motor draws
more current in an attempt to produce more
energy to meet the increased motor load. The
additional current increases the temperature
inside the motor. Higher than normal
temperatures will cause damage to the motor.

Motor Nameplate

This plate is attached to each motor. It provides
motor information and specifications, such as
horsepower, full load current, service factor,
voltage and frequency, and the type of current.
The motor nameplate is a primary source for
information necessary to select control products.

Motor Load

The energy that a machine requires from a
motor in order to operate, measured in torque.

Minimum Speed

The setting on the drive which determines the
lowest frequency that the drive will output.

Mid-Tap (transformers)

A reduced-capacity tap midway in a winding -
usually the secondary.

Meggar Test

A test used to measure an insulation system’s
resistance. This is usually measured in
megohms and tested by passing a high voltage
at low current through the motor windings and
measuring the resistance of the various
insulation systems.

Maximum Speed

The setting on the drive which determines the
highest frequency that the drive will output.

Main Circuit Breaker

Switch which is connected to the main bus bars
that can disconnect power to the entire load
center.

Main Bus Bars

Main conductors of electricity, which are inside
the load center, are composed of copper or
aluminum strips.

LRC (motor) Locked Rotor Current

Locked Rotor Current. This is the amount of
electrical current required to start and accelerate
a motor to its rated speed. Locked rotor current
may also be called locked rotor amps (LRA) or
inrush current. A motor’s LRC is used when
selecting motor overload protection devices.

Low power factor (I/R)

When the non-working power is a large
component of the total power, such as lightly
loaded motors, the power factor could be .5 or
50%, which would be a ratio of 1/2 or 50%
power factor.

Logic Devices

They receive electrical signals from input
devices and make decisions based on preset
information. They then send electrical signals to
output devices. Examples of logic devices are
relays, timers and programmable logic
controllers.

Locked-Rotor Torque

The minimum torque that a motor will develop
at rest for all angular positions of the rotor (with
rated voltage applied at rated frequency).

Locked-Rotor Current

Steady state current taken from the line with the
rotor at standstill (at rated voltage and
frequency). This is the current when starting the
motor and load.

Load (transformers)

Expression of power in KVA or volt amperessupplied
by the transformer.

Load Center

A box for the distribution of electrical current
located either inside or outside the house which
connects to the service entrance conductors.
Often mistakenly called a “circuit breaker box”
or “fuse panel”. The proper name is a load
center.

Load (electrical)

An electrical path of varying resistance which
connects to the electrical system. Loads are any
device which uses electricity. For example,
appliances or lights.

Load (Mechanical)

External resistance to movement that must be
overcome by a motor , under a given condition,
measured in the power required.

Liquid-Immersed Transformer

Transformer with core and coils immersed in
liquid (as opposed to a dry-type transformer).

Linear Loads

The waveform of the current is the same as the
waveform of the voltage.

Linearity

A measure of how closely a characteristic
follows a straight line function.

Linear Acceleration/Deceleration

(LAD) A circuit that controls the rate at which
the motor is allowed to accelerate to a set speed
or decelerate to zero speed. On most drives,
this circuit is adjustable and can be set to
accommodate a particular application.

Limit Switch (motor control)

This is one type of input device. It is a type of
sensor that is designed to detect physical
contact with an object.

Kinetic Energy

The energy of motion possessed by a body.

KW (kilowatts)

Active or working power is the power which is
converted into useful work.

KVAR (kilovars)

Reactive or non-working power provides the
magnetic flux necessary for the operation of the
device but is not transformed into any useful
work.

KVA or Volt-Ampere Output

The KVA or volt-ampere rating designates the
output which a transformer can deliver for a
specified time at rated secondary voltage and
rated frequency without exceeding the specified
temperature rise (1KVA=1000-VA).

K Factor (power conditioning, transformers)

Refers to specially designed transformers that
can withstand harsh harmonic currents,
particularly in the neutral conductor.

Jogging

Jogging is a means of accomplishing
momentary motor movement by repetitive
closure of a circuit using a single push-button or
contact element.

Isolation Transformer

A transformer that electrically separates the
drive from the AC power line. An isolation
transformer provides the following advantages:
1. In DC motor applications, it guards against
inadvertent grounding of plant power lines
through grounds in the DC motor armature
circuit.
2. Enhances protection of semiconductors from
line voltage transients.
3. Reduces disturbances from other solid state
control equipment such as drives without
isolation transformers, time clock systems,
electronic counters, etc.

IR Compensation

A way to compensate for the voltage drop
across resistance of the AC or DC motor circuit
and the resultant reduction in speed. This
compensation also provides a way to improve
the speed regulation characteristics of the
motor, especially at low speeds. Drives that use
a tachometer-generator for speed feedback
generally do not require and IR compensation
circuit because the tachometer will inherently
compensate for the loss in speed.

IPM Intelligent Power Module

(Intelligent Power Module) Module which
contains IGBT’s and “intelligent” switching
circuit. The IPM can be used as a self-contained
inverter.

IOC Instantaneous Over-Current

(Instantaneous Over-Current) IOC is a fault
condition that occurs when an excessive
amount of current passes through the drive.
This type of fault occurs when the current
exceeds the current rating of the drive by 250%
to 350%. Unlike an overload condition, IOC will
trip the drive instantaneously.

Inverter (UPS)

This is the circuit in a UPS that converts DC
voltage from the battery into AC voltage for the
load.

Inverter (AC Drive)

A term commonly used for an AC adjustable
frequency drive. An inverter is also a term used
to describe a particular section of an AC drive.
This section uses the DC voltage from a
previous stage (Intermediate DC Circuit) to
produce an AC current or voltage having the
desired frequency.

Intermittent Duty

(INT) A motor that never reached equilibrium
temperature (equilibrium), but is permitted to
cool down between operations. For example, a
crane, hoist, or machine tool motor is often
rated for 15 or 30 duty.

Integral Main (lighting panels)

The main disconnect device is inside the
panelboard.

Integral Horsepower Motor

A motor built in a frame having a continuous
rating of 1 HP or more.

Insulation System

Balancing of insulation materials to properly
insulate a given product.

Isolation (power conditioning)

The magnetic separation of the input and output
of a transformer device with a grounded shield
in between them.

Insulator

Materials that do not allow current to flow easily.
It is wrapped around individual wires to prevent
the current flow to undesirable places.

Instability

The state or property of a system where there is
an output but no corresponding input.

Inrush (motor)

High initial peak of current occurring during the
first few cycles of motor energization.

Input devices (motor control)

Control products that start the initial action of a
control system. These devices send electrical
signals to a second type of product called logic
devices.

Inertia

A measure of a body’s resistance to changes in
velocity, whether the body is at rest or moving
at a constant velocity. The velocity can be either
linear or rotational. The movement of Inertia
(WK2) is the product of the weight (W) of an
object and the square of the radius of gyration
(K2). The radius of gyration is a measure of how
the mass of the object is distributed about the
axis of rotation. WK2 is usually expressed in
units of lb-ft2.

Inductive Loads

Any type of load that has a coil of wire as the
current-drawing element (i.e. motor winding,
ballast, transformer).

Induction Motor

An alternating current motor in which the
primary winding on one member (usually the
stator) is connected to the power source. A
secondary winding on the other member
(usually the rotor) carries the induced current.
There is no physical electrical connection to the
secondary winding, its current is induced.

Impedance (%IZ)

Retarding forces of current flow in ac circuits.
With respect to transformers, it is the measure
of the transformer’s resistance and reactance to
current flow.

IGBT Insulated Gate Bipolar Transistor

(Insulated Gate Bipolar Transistor) - Type of
power device frequently used in inverter
sections of drives. The IGBT is noted for its
ease in switching on and off and high switching
frequencies.

IEEE

Institute of Electrical and Electronic Engineers.

Hysteresis Loss

The resistance offered by materials to becoming
magnetized results in energy being expended
and corresponding loss. Hysteresis loss in a
magnetic circuit is the energy expended to
magnetize and demagnetize the core.

Hunting

Undesirable fluctuations in motor speed that can
occur after a step change in speed reference
(either acceleration or deceleration) or load.

Horsepower

The amount of work done by a machine.
Relative to motors, horsepower Indicates the
power of the motor. Motor horsepower is a
selection criterion for motor control products
such as manual and magnetic motor starters.

High Power Factor

When the active power component equals or is
very near to the total power such as for a purely
resistive load, the highest power factor possible
would be 1.0, or 100% unity.

Hertz

A unit of frequency equal to one cycle per
second. Abbreviated Hz.

Harmonic

A component frequency of a current or voltage
that is an integral multiple of the fundamental
frequency.

General-Purpose Motor

This motor has a continuous Class “B” rating
and design, listed and offered in standard
ratings with standard operating characteristics
and mechanical construction for use under usual
service conditions without restriction to a
particular application or type of application
(NEMA).

GTO

Gate turn-off or gate turn-on power
semiconductor device.

Generators

Large machines which produce electricity.
Generators are found in electrical power plants.

Gate

The control element of an SCR (silicon
controlled rectifier) commonly referred to as a
thyristor. When a small positive voltage is
applied to the gate momentarily, the SCR will
conduct current (when the anode is positive with
respect to the cathode of the SCR). Current
conduction will continue even after the gate
signal is removed.

Fully Rated System (circuit breakers)

In this system, the interrupting rating of all
overcurrent protective devices must be greater
than or equal to the available fault current at the
lineside terminals of each device.

Fully Rated Selectively Coordinated

This is a fully rated system with an additional
system (circuit breakers) design characteristic:
within the range of selectivity, overcurrent
protective device closest to the fault, opens the
circuit, while the upstream overcurrent
protective device remains closed. This limits
unnecessary interruption of service to
unaffected portions of the system. A system
coordination study may be advisable to assure
optimum selectivity.

Full-Load Torque

The full-load torque of a motor is the torque
necessary to produce rated horsepower at fullload
speed.

FLC (motor control)

This is the electrical current required during
normal motor operation to generate its designed
horsepower. Full load current is also known as
full load amps (FLA). A motor’s full load current
is used when selecting motor overload
protection devices.

Full-Capacity Tap (transformers)

Tap through which the transformer can deliver
its rated KVA output without exceeding the
specified temperature rise.

Frequency

The number of cycles per second for an AC
electric system; the number of times per second
that the current flow changes direction.

Four-Quadrant Operation

The four combinations of forward and reverse
rotation and forward and reverse torque of
which a regenerative drive is capable. The four
combinations are:
1. Forward rotation/forward torque (motoring)
2. Forward rotation/reverse torque regeneration)
3. Reverse rotation/reverse torque (motoring)
4. Reverse rotation/forward torque regeneration)

Force

The tendency to change the motion or position
of an object with a push or pull. Force is
measured in ounces or pounds.

Filter

A device that passes a signal or a range of
signals and eliminates all others.

Eye-Bolt Bushing

Bushing with integral screw clamp for one cable
only.

Exciting Current

Current which flows in any winding used to
excite the transformer when all other windings
are open-circuited and is usually expressed in
percent of the rated current of a winding in
which it is measured.

Excitation Current

The steady state current that keeps the
transformer energized after the inrush has
dissipated.

Error

Difference between the set point signal and the
feedback signal. An error is necessary before a
correction can be made in a controlled system.

Encoder

An electromechanical transducer that produces
a serial or parallel digital indication of
mechanical angle or displacement. Essentially,
an encoder provides high resolution feedback
data related to shaft position and is used with
other circuitry to indicate velocity and direction.
The encoder produces discrete electrical pulses
during each increment of shaft rotation.

Encapsulated Winding (transformers)

Transformer having coils either dipped or cast in
an epoxy resin.

Enable

To allow an action or acceptance of data by
applying an appropriate signal to the appropriate
input.

motor control centers

Includes a removable undrilled panel with a
hinged door to provide space for customerinstalled
devices in a Motor Control Center.

Electrostatic Shield (transformers)

Copper or other conducting sheet placed
between primary and secondary and grounded
to provide additional protection against electrical
interference.

Electrical Service

Supply power from the utility.

Efficiency Efficiency (transformers)

Efficiency
Ratio of mechanical output to electrical input
indicated by a percent. In motors, it is the
effectiveness with which a motor converts
electrical energy into mechanical energy.

Efficiency (transformers)
The efficiency of a transformer is the energy
output expressed as a percentage of the energy
input and reflects the losses within the
transformer. For loads between 25% and 150%
of rating efficiencies between 98% and 99.5%
would not be untypical.

Eddy Current

Currents induced in motor components from the
movement of magnetic fields. Eddy currents
produce waste heat and are minimized by
lamination of the motor poles and armature.

Dwell EEMAC

Dwell
The time spent in one state before moving to
the next. In motion control applications for
example, a dwell time may be programmed to
allow time for a tool change or part clamping
operation.

EEMAC
Acronym for Electrical and Electronic
Manufacturer's Association of Canada. Similar
to NEMA in the U.S.

dv/dt

The rate of change in voltage versus a rate of
change in time. Specially designed Resistor-
Capacitor networks can help protect the SCRs
from excessive dv/dt which can result from line
voltage spikes, line disturbances and circuit
configurations with extreme forward conducting
or reverse blocking requirements.

Dusttight DutyCycle

Dusttight
"Dusttight" means that a device is so
constructed so that dust will not enter the
enclosure case under specified test conditions.

DutyCycle
The relationship between the operating and rest
times or repeatable operation at different loads.

Dry Type (transformers)

A dry type transformer is one in which the
transformer core and coils are immersed in air
or other dry gas.

Drive Controller

(Also called Variable Speed Drive) An electronic
device that can control the speed, torque,
horsepower and direction of an AC or DC motor.

Driptight

"Driptight" means that a device is so constructed
or protected as to excluded falling dirt or drops
of liquid under specified test conditions.

Drift

Drift is the deviation from the initial set speed
with no load change over a specific time period.
Normally the drive must be operated for a
specified warm-up time at a specified ambient
temperature before drift specifications apply.
Drift is normally caused by random changes in
operating characteristics of various control
components

Double or Split Door (lighting panels)

In a lighting contactor panel, one door is used to
cover the contactor and the other is used to
cove the branch breakers.

Door-In-Door (lighting panels)

Trim has an inner door over the branch
disconnect area secured with one latch. An
outer door covers the gutter area also secured
by a single latch. There is another flange around
the entire box.

Direct current

This can be produced from alternating current or
supplied as a direct output from a battery. Direct
current always flows in the same direction. In
the United States, direct current powers cranes
and other industrial equipment. The
abbreviation for direct current is “DC”.

Distribution Transformers

Transformers rated 500KVA and below are
usually referred to as distribution type.
Exceptions include current and potential and
other specialty transformers.

Diode

A device that passes current in one direction,
but blocks current in the reversed direction.

Dielectric

Insulator such as glass, rubber, plastic, etc. that
separates two electrical conductors in a
transformer or capacitor, for example.

di/dt

The rate of change in current versus a rate of
change in time. Line reactors and isolation
transformers can be used to provide the
impedance necessary to reduce the harmful
effects that unlimited current sources can have
on phase controlled rectifiers (SCRs).

“D” Flange (Motor Mounting)

This type of motor mounting is used when the
motor is to be built as part of the machine. The
mounting holes of the flange are not threaded.
The bolts protrude through the flange from the
motor side. Normally “D” flange motors are
supplied without feet since the motor is mounted
directly to the driven machine.

Deviation

Difference between an instantaneous value of a
controlled variable and the desired value of the
controlled variable corresponding to the set
point. Also called error.

Delta-Wye

A term or symbol indicating the primary
connected in delta and the secondary in Wye
when pertaining to a three-phase transformer or
transformer bank.

Delta Voltage System

This system provides three phases and three
wires, three “hot” wires. 240 volt and 480 volt
are the most commonly used delta systems.

Delta (D)

A standard three-phase connection with the
ends of each phase winding connected in series
to form a closed loop with each phase 120
degrees from the other. Sometimes referred to
as 3-wire.

Decibel (dB)

A term used in sound measurement. A change
of one dB in sound level is the smallest change
the human ear can detect. A busy office might
measure from 65-70 dB. dB is a measure of
sound intensity.

Dead Band

The range of values through which a system
input can be changed without causing a
corresponding change in system output.

Damping

Damping is the reduction in amplitude of an
oscillation in the system.

Current-Limiting Circuit Breaker

A circuit breaker that does not use a fusible
element and when operating within its current
limiting range, limits the let through current
within predetermined acceptable values.

Current Limiting

An electronic method of limiting the maximum
current available to the motor. This is adjustable
so that the motor’s maximum current can be
controlled. It can also be preset as a protective
device to protect both the motor and control
from extended overloads.

Current (represented as an “I”)

The flow of electrons. Current is measured in
amperes, (commonly abbreviated as “amps”).

Current (electrical service)

Alternating current (AC) or direct current (DC)

CSA Canadian Standards Association.

Canadian Standards Association.

Corrosion Resistant

"Corrosion Resistant" means that a device is so
constructed, protected, or treated that corrosion
will not exceed specified limits under specific
test conditions.

Core Loss (transformers)

The energy lost in the transformer needed to
magnetize the core. Expressed in watts of KW
(1000 watts). Core loss is constant and
independent of transformer load. It is present all
the time a transformer is energized. (See also
Iron Loss, No-Load Loss.)

Converter

The process of changing AC to DC. This is
accomplished through the use of a diode
rectifier or thyristor rectifier circuit. The term
“converter” may also refer to the process of
changing AC to DC to AC (e.g. adjustable
frequency drive). A “frequency converter”, such
as that found in an adjustable frequency drive,
consists of a Rectifier, a DC Intermediate
Circuit, an Inverter and a Control Unit

Continuous Rating

Defines the constant load which a transformer
can carry at rated primary voltage and
frequency without exceeding the specified
temperature rise.

Continuous Load

A load where the maximum current is expected
to continue for three hours or more.

Continuous Duty

(CONT) A motor that can continue to operate
within the insulation temperature limits after it
has reached normal operating (equilibrium)
temperature.

Continuous current rating (handle rating)

The maximum direct current or rms current in
[circuit breakers] amperes, at a rated frequency
which a device or an assembly will carry
continuously without exceeding the specified
limits of observable temperature rise.

Contactor Reversing

A method of reversing motor rotation by the use
of two separate contactors, one of which
produces rotation in one direction and the other
produces rotation in the opposite direction. The
contactors are electrically (and mechanically)
interlocked so that both cannot be energized at
the same time.

Constant Volts per Hertz (V/Hz)

This relationship exists in AC drives where the
output voltage is varied directly proportional to
frequency. This type of operation is required to
allow the motor to produce constant rated torque
as speed is varied.

Constant Voltage Range

(AC Drives) The range of motor operation where
the drive’s output voltage is held constant as the
output frequency is varied. This speed range
produces motor performance similar to a DC
drive’s constant horsepower range.

Constant Torque Range

A speed range in which the motor is capable of
delivering a constant torque, subject to the
cooling limitations of the motor.

Constant Horsepower Range

A range of motor operation where motor speed
is controlled by field weakening. In this range,
motor torque decreases as speed increases.
Since horsepower is speed times torque
(divided by a constant), the value of horsepower
developed by the motor is this range is constant.

Conductor

Materials that allow current to flow easily. The
“pipe” for electrons.

Compartment

Space (air-filled) in which to terminate cable.

Comparator

A device that compares one signal to another.
This is usually the process signal which is
compared to the set point or command signal.

Commutation (Inverter)

The process by which forward current is
interrupted or transferred from one switching
device to the other. In most circuits where power
is supplied from an AC source, turn-on control is
adequate and turn-off occurs naturally when the
AC cycle causes the polarity across a given
device to reverse.

Common Trim (lighting panels)

One piece of sheet metal which covers two
panel boards mounted side by side.

Common Mode Noise (power conditioning)

This is electrical interference that occurs
between the hot wire and ground, or the neutral
wire and ground.

Cogging

A condition in which a motor does not rotate
smoothly but “steps” or “jerks” from one position
to another during shaft revolution. Cogging is
most pronounced at low motor speeds and can
cause objectionable vibrations in the driven
machine.

Closed Loop

Closed loop refers to a regulator circuit in which
the actual value of the controlled variable (e.g.
speed) is sensed and a signal proportional to
this value (feedback signal) is compared with a
signal proportional to the desired value
(reference signal). The difference between
these signals (error signal) causes the actual
value to change in the direction that will reduce
the difference in signals to zero.

Circuit Breaker Frame

1. The circuit breaker housing that contains the
current carrying components, the current
sensing components and the tripping and
operating mechanism. 2. That portion of an
interchangeable trip circuit breaker remaining
when the interchangeable trip unit is removed.

Circuit Breaker

A device designed to open and close a circuit by
non-automatic means and to open the circuit
automatically on a predetermined overcurrent
without damage to itself when properly applied
within its rating.

Cellular Steel Floor System (wire mgmt.)

Corrugated sheet metal floor decking which can
be used as electrical raceway.

Case (motor)in

The external housing of the motor

Cable Tray (wire mgmt.)

An economical system for supporting cables
and wires.

“C” Face (Motor Mounting)

This type of motor mounting is used to close
couple pumps and similar applications where
the mounting holes in the face are threaded to
receive bolts from the pump. Normally, the “C”
face is used where a pump or similar item is to
be overhung on the motor. This type of
mounting is a NEMA standard design and
available with or without feet.

Bushing (m.v. transformers)

Conductor extending through the tank wall with
liquid-tight fittings for connecting electrical
internal parts to exterior cables.

Bridge Rectifier (Diode, SCR)

A diode bridge rectifier is a non-controlled full
wave rectifier that produced a constant rectified
DC voltage. An SCR bridge rectifier is a full
wave rectifier with an output that can be
controlled by switching on the gate control
element.

Bridge Rectifier

A full wave rectifier that conducts current in only
one direction of the input current. AC applied to
the input results in approximate DC at the
output.

Breakdown Torque

The breakdown torque of an AC motor is the
maximum torque which it will develop with rated
voltage applied at the rated frequency.

Breakaway Torque

The torque required to start a machine from
standstill. It is always greater than the torque
needed to maintain motion.

Motor Mounted or Separately Mounted Brake

C. Motor Mounted or Separately Mounted Brake
--- is a positive action, mechanical, friction
device. Normal configuration is such that
when the power is removed, the brake is set.
This can be used as a holding brake. (Note:
A Separately Mounted Brake is one which is
located on some part of the mechanical drive
train other than the motor.)

Regenerative Braking

B. Regenerative Braking --- is similar to
Dynamic Braking, but is accomplished
electronically. The generated power is
returned to the line through the power
converter. It may also be dissipated as losses
in the converter (within its limitations).

Dynamic Braking (DC Drives)

A. Dynamic Braking (DC Drives) --- slows the
motor by applying a resistive load across the
armature leads after disconnection from the
DC supply. This must be done while the
motor field is energized. The motor then acts
as a generator until the energy of the rotating
armature is dissipated. This is not a holding
brake.
Dynamic Braking (AC Drives) --- Since AC
motors do not have separate field excitation,
dynamic braking is accomplished by
continuing to excite the motor from the drive.
This causes a regenerative current to the
drive’s DC Intermediate Bus Circuit. The
Dynamic Brake resistors are then placed
across the DC bus to dissipate the power
returned. The brake resistor is usually
switched by a transistor or other power switch
controlled by the drive.

Breaking

Breaking provides a means of stopping an AC
or DC motor and can be accomplished in
several ways:

Branch Circuit Breaker

Switch which is connected to the main circuit
path and the first load in the branch. It is used to
turn off power to that branch circuit.

Branch Circuit

An electrical path which connects to the main
electrical path. If a branch is disconnected from
the main branch only the load connected to that
branch looses power. All other branches are not
affected by the disconnection.

Bolt-on Connection (motor control centers)

Interior device is cable-connected directly to the
horizontal bus by means of bolted connection.

BIL

Basic Insulation Level. A specific insulation
level expressed in kilovolts of the crest value of
a standard lightning impulse.

Roller Bearing

A special bearing system with cylindrical rollers
capable of handling belted load applications, too
large for the output shaft.

Ball Bearing

A “ball” shaped component that is used to
reduce friction and wear while supporting
rotating elements. For a motor, this type of
bearing provides a relatively rigid support for the
output shaft.

Base Speed

Base speed is the manufacturer’s nameplate
rating where the motor will develop rated HP at
rated load and voltage. With DC drives, it is
commonly the point where full armature voltage
is applied with full rated field excitation. With
AC systems, it is commonly the point where 60
Hz is applied to the induction motor.

Bandwidth

Generally, frequency range of system input over
which the system will respond satisfactorily to a
command.

Back of a Motor

The back of a motor is the end which carries the
coupling or driving pulley (NEMA). This is
sometimes called the drive end (D.E.) or pulley
end (P.E.).

Axis

A principle direction along which movement of
the tool or workpiece occurs. The term axis also
refers to one of the reference lines of a
coordinate system.

Automatic Protection Circuit

A device which automatically (no human action
needed) disconnects power. For an example, a
circuit breaker is both a manual and automatic
device. A person can manually open a circuit
breaker or it can automatically open if it senses
an overcurrent condition.

ATC (m.v. transformers)

Air terminal compartment (i.e., air-filled as
opposed to oil-filled). Space in which to
terminate cable connections to a transformer.

ASTM

American Society for Testing Materials

Armature (motor)

An assembly composed of the rotor and the shaft

ANSI 49

Shade of gray paint color. Standard means of
describing paint color with the number indicating
the percentage of reflected light. (ANSI 0 would
be black, ANSI 100, totally reflective).

ANSI American National Standards Institute ANSI 49

American National Standards Institute
ANSI 49

Ambient Temperature Rating

Temperature at which the continuous current
rating (handle rating) of a circuit is based; the
temperature of the air immediately surrounding
the circuit breaker that can affect the thermal
(overload) tripping characteristics of a thermalmagnetic
circuit breaker. Electronic trip circuit
breakers, however, are insensitive to normal (-
5o to 50o C) ambient conditions. UL standard
489 listed circuit breakers have an ambient
temperature rating of 40o C.

Ambient Temperature

Temperature of the surrounding atmosphere
into which the heat of any electrical product is
dissipated.

Ambient Noise Level

The noise level of the surrounding area
measured in decibels.

Alternating current

This is the most common type of current used
today. In the United States, all electricity is
generated as alternating current. It is called
alternating current because first the current
flows in one direction then it will flow in the
opposite direction and so on. The current
alternates between two opposite directions. (It is
often represented by a side-ways “s”) Alternating
current is used in homes for lighting, heating,
cooking, and operating appliances. Industry
uses it primarily to operate motors but also for
lighting and equipment operation. The
abbreviation for alternating current is “AC”.