Single-phase motors are not widely used for reversing operation. In fact, these are not even available widely
with reversing capability.
As here we have a three-phase AC motor, reversing any two leads will drive the motor in reverse direction.
Contactor is an electrical switch used for switching an electrical power circuit.
Two magnetic contactors are used, one for forward connections and the other for reverse connections.
Only Push Button switches are used to control the direction of this three-phase AC motor.
We have the input commands to these Push Button switches which are then internally processed by PLC
and then there is the output terminal which activates the corresponding relay to energize the relevant magnetic
contactors.
Configure forward and reverse wiring of the motor with contactors such that forward contactor is connected
directly in the normal direct phasing of the motor terminal and reverse contactor is connected with two of the
motor terminals in the opposite phase.
When it is switched to reverse direction, forward rotation does not stop instantaneously hence we have to
determine what time it takes to completely stop one particular direction. Then provide time delay of a second or
two and activate the other contactor.
PLC Program
Here is PLC program to Drive Motor in Forward and Reverse Direction, along with program explanation
and run time test cases.
List
of Inputs and Outputs
I:1/0
=
Forward Start
(Input)
I:1/1
=
Reverse Start
(Input)
I:1/2
= Stop
(Input)
O:2/14
= Latched coil 1
for forward direction
(Output)
O:2/0 & O:2/1
=
Forward Contactor
(Output)
T4:1
= Delay before forward direction (Timer)
O:2/15
= Latched coil 2
for reverse direction
(Output)
O:2/2 & O:2/3
=
Reverse Contactor
(Output)
T4:0
= Delay before reverse direction (Timer)