SINAMICS S120 AC Drive

 SINAMICS S120 AC Drives – a building block
for integrated drive solutions
SINAMICS S120 is a modular drive system with Servo and
Vector Control and is the SINAMICS product most suitable for
demanding drive applications. The stand-alone SINAMICS
S120 AC Drives complement the DC/AC units, which use a
common infeed and controller designed especially for
multi-axis applications. Optimally tailored, integrated solutions can be designed for any type of application based on this
building block system.
The ready-to-connect SINAMICS single drive
SINAMICS S120 AC Drives are designed for single-axis applications but can also be used for multi-axis applications.
Positioning tasks can be reliably executed as well as synchronous movements and motion control tasks. In multi-axis
applications with spatially distributed drives, distributed
solutions based on SINAMICS S120 AC Drives offer a practical
alternative to a central drives line-up.
Universally implementable
SINAMICS S120 AC Drives can easily be implemented in conjunction with higher-level automation systems using field bus
interfaces and the standardized PROFIdrive profile. Solutions
to standard positioning tasks – especially in the SIMATIC PLC
environment – can therefore be found using SINAMICS S120
AC Drives even without in-depth knowledge of drives.
Because it is so easy to combine SINAMICS S120 AC Drives
with other SINAMICS S120 units, multi-axis groupings can be
extended comfortably and economically.
Modular machine components can thus be adapted to high
levels of integration and flexibility in line to varying customer
requirements.
Flexibility through modularity
Every SINAMICS S120 AC Drive is a combination of a Power
Module and a selectable Control Unit or Control Unit Adapter.
An optional filter can also be integrated.
If the AC Drive is operated as a stand-alone single-axis drive,
a Control Unit (e.g. CU310 DP) is added to the Power Module.
It contains the entire control intelligence for the drive, including positioning functions and the field bus interface.
If the AC Drive is combined with other SINAMICS S120 units
to build an integrated multi-axis drive solution, a CUA31 Control Unit Adapter is added to the Power Module in order to
connect the AC Drive to a central Control Unit (e.g. CU320 or
SIMOTION D) via the DRIVE-CLiQ interface in accordance with
the SINAMICS S120 system architecture.
With SINAMICS S120 the modular expansion of your machines
is never limited. Cost-optimized and specific solutions are
ensured since only the components and functions required for
a perfect fit solution are used.

ac-drives The perfect solution – quickly and reliably

Complete drive groups can be interlinked
and assembled using the SINAMICS S120
Cabinet Modules and Chassis units. This
is because it is possible to combine module types with freely selectable power
ratings as required. Fast and straightforward, due to the standard interfaces that
are harmonized with one another.
For paper machines, rolling mills, test
stands and cranes – that typically require
multi-motor applications with high power
ratings, both the modular cabinet units as
well as also the Chassis units are the ideal
solution as part of a modular system.
The highly flexible, modular system follows the trend to shift intelligence into
the drive, which is achieved using its harmonized, standard interfaces. Planning is
simplified and reliability increased thanks
to the ready-to-connect cabinet solution
with several Cabinet Modules. The chassis
design of the SINAMICS S120 is the ideal
approach for companies that wish to engineer their own chassis-type solutions.

SINAMICS S120 – AC Drives for single-axis applications

AC Drives for
single-axis applications
•  An autonomous single-axis
SINAMICS S120 AC Drive comprises
a Control Unit and Power Module
•  Alternatively, a Power Module can
be integrated into a multi-axis
group via CU adapter
•  Power Modules are available in the
Blocksize and Chassis formats
Typical applications
Single-axis drives are suitable for applications in all sectors, such as e.g. for travel
drives, centrifuges, elevators and extruders as well as for mixers and kneaders.
Single-axis SINAMICS S120 AC Drives are
also the ideal solution for multi-axis applications where the drive axes are located remotely from one another. The same
applies to modular machine concepts
that are being increasingly implemented
in the packaging and woodworking industries.
For a single-axis drive, the line supply
infeed and the power supply of the motor are combined in one device – the
so-called Power Module. For single-axis
applications, a special Control Unit (e.g.
CU310) mounted on the Power Module
handles the drive control; for multi-axis
applications a Control Unit is used (e.g.
CU320) coupled through DRIVE-CLiQ.
In the latter case, instead of the Control
Unit, a CU Adapter is mounted on the
Power Module.
For instance, SINAMICS S120 AC Drives
decentrally coupled to a higher-level
control via PROFIBUS DP or PROFINET can
reliably handle e.g. positioning tasks in
automated assembly machines and handling systems.

Digital microprocessor-controlled power converter technology

Digital microprocessor-controlled power converter technology, both for DC and AC drives, has
now reached a level of technical sophistication
which (in purely technological terms) enables
almost any drive job to be handled both with DC
and AC drives. Nevertheless, the conventional
DC drive (in both its 1-quadrant and 4-quadrant
variants) will continue to play an important role,
for technical and physical reasons alike, when
dynamic drives with a constant load torque and
stringent requirements for overload withstand
capability throughout a large speed setting range
are involved.

Efficiency and operating point of DC and AC standard motors

The motor constant makes it possible to design the nominal point of DC motors corresponding to the process requirements.
However the efficiency of AC motors is better (> 55 kW: approx. 1 ... 4 % depending on cooling method).
DC motors are often utilized according to insulation class H. Standard AC motors are used to be utilized according to insulation
class B. This results in a possible higher efficency with AC motors.

Mains pollution: ac drive

The line currents of DC drives with a 6-pulse thyristor bridge will always contain, in addition to the fundamental wave, the 5th,
7th, 11th and 13th harmonics with empirical values of 22 %, 14 %, 9 %, 7.6 % , referenced to the fundamental wave. In the
case of several DC drives operating simultaneously on the mains, the different phase sequences of the harmonic currents will
produce a "statistical improvement" in the level of mains pollution.
Due to the dimensioning method adopted for the smoothing inductors, harmonic currents with contents of 40 %, 14 %, 9 %
and 7.6 % must be anticipated with AC drives featuring a 6-pulse diode bridge in 1-quadrant drives. Due to the identical phase
angle of the harmonic currents, several drives on the same mains can be regarded as one drive with the same total current.This
also applies for thyristor bridges in 4-quadrant operation.
Input bridges with IGBT switching elements enable the low-frequency harmonics to be substantially reduced, but conversely
create more high-frequency harmonics.

Reactive-power demand

Both drive concepts (AC and DC) take reactive power from the mains. Its size is negligible in the case of AC drives, and is RPMdependent below the rated speed with DC drives. The AC drive is the more favourable option here.
Values obtained from empirical feedback:
For AC drives, the value for cos ϕ
1
 is in
1-quadrant applications
with diode bridge cos ϕ
1
 ≈ 0.99
4-quadrant applications
with thyristor bridge and
with energy recovery into the mains cos ϕ
1
 ≈ 0.9
Values obtained from empirical feedback:
For DC drives, the value for cos ϕ
1
 is in
1-quadrant applications cos ϕ
1
 ≈ 0...0.9
4-quadrant applications cos ϕ
1
 ≈ 0...0.85

Modernization of existing DC drive

When it comes to the question of whether it is worth while
modernizing an existing DC drive or less expensive to replace
it entirely with an AC drive, there are also various arguments
which need to be assessed:
Basically, there are several options available for a modernization job:
1. Replace the entire DC drive (converter and motor) by a new
DC drive.
2. Replace only the converter cubicle, if the motor is still in
good condition.
3. Replace the converter module by a modern digital unit.
4. Replace the old, analog drive electronics by new, digital
electronics while continuing to use the power section
(recommended only for ratings above 1 MW).
5. Replace the entire drive system with a new AC drive.
When answering the question of what approach constitutes
the optimum solution in a particular case, the following main
criteria are important:
Will the requirements for the drive change in future (load
requirements, environmental conditions)?
In what condition are the individual components of the
system (reliability, age, maintenance outlay)?
How far will the supply conditions change in future?
Before a decision is made to modify a drive from DC to AC
design, the following points should be taken into consideration:
Outlay for new power cabling.
Space requirements for converter cubicles.
Dissipation of energy losses from the switchroom sufficient?
Foundations, mounting for motor sufficient?
Space requirement for new motor.
Duration of conversion work.

Price comparison DC and AC drive systems

(unit + motor or complete switchgear cabinet  + motor)
Based on the present-day development status of DC and AC drive engineering, and taking into account all the
systems' advantages/disadvantages mentioned above, the following guideline figures can be given:
1-quadrant drives <40...80 kW ê AC drives less expensive
4-quadrant drives >40...60 kW
(AC converter +  braking resistor; see Fig. 10); ê DC drives less expensive
Regenerative 4-quadrant drives > 15 kW ê DC drives less expensive