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How to Reverse a Contactor for a Permanent Magnet Motor

Contactors are special relays used to control electric motors. These devices are designed to handle 100 amps or higher current levels depending on the type purchased. DC contactors are used to switch large permanent magnet DC motors on and off as needed. Reversing a contactor is needed when it is necessary to reverse the motor's direction of rotation. This would be useful on a conveyor belt. How a contactor is reversed depends on the contactor design.

Things You'll Need

DC contactor
Electrical wire
Screwdriver
Wire stripper
Wire cutter

Instructions

- 1
  Shut off power to the DC circuit powering the motor and contactor. Check the contactor documentation which will indicate how to reverse the contactor. Different contactors have different methods of reversing.
- 2
  Check the contactor to see if it has terminals for reversing. If not, reverse the contactor by reversing either the source terminals of the contactor or the load terminals, but not both. For example, if terminal "A" and terminal "B" are the terminals on the contactor that feed the black and white wires of the motor respectively, reverse the contactor by using the screwdriver to disconnect the black wire on terminal "A" and the white wire of terminal "B." Then connect the black wire to terminal "B" and the white wire to terminal "A." If the contactor has reversing terminals, skip this step and go to Step 3.
- 3
  Cut a wire long enough to reach each of the two reversing terminals. Strip one-half inch of insulation off of each end of the wire. Connect the two reversing terminals together using this wire.
- 4
  Double check your wiring and check contactor documentation before turning the power back on. After checking the wiring, turn the power back on and test the motor's operation and direction of rotation.

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