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.