Dumpmaster - Troubleshooting a non-operational motor on a mains-powered machine

The 0.75kW AC electric motors fitted to 3-phase mains powered Dumpmasters are generally very reliable and require no maintenance. If the motor will not run on a 3-phase machine, potential faults include:

• The door not shutting properly, or the contact strip (at the top of the hinge side of the door) not connecting with the side guard, or the pin at the bottom left corner of the door not connecting with the contact plate inside the plastic end-cap.
• Faulty key switch, Emergency Stop (if fitted), or Raise switch.
• Loose or disconnected wires.
• Faulty contactor coil or sticking contacts.
• Faulty motor, or capacitor (1-phase motors only).

Test procedures

1. Firstly, check the power supply to the machine. If it is 3-phase, check that all phases are working.
2. Set a multi-meter to read ac voltage, and test whether there is voltage between the pink wire on one of the fuse holders and the mounting plate in the enclosure.
3. If there is no voltage reading, check the fuses. There are 2 – one before the step-down transformer (400 or 240v) and one after it (24v).
4. If OK, check the voltage at the 2 contactor switching terminals when the Raise button is pressed and the door closed (if a door is fitted). There should be approx. 24vac.
5. If there is voltage there but the contactor does not pull in, try moving the tab in the center by hand, to make sure it hasn’t jammed. If there is voltage and the contactor is not jammed, it probably needs to be replaced.
6. If the contactor pulls in but the motor does not run, press the overload reset button at the bottom of the enclosure. If the motor still doesn’t run, check that no wires have been pulled out of the contactor or the motor.
7. If there is no voltage at the contactor switching terminals, identify which side is not sending current:
   1. Keep one probe on the bottom terminal (with the blue wire) and hold the other wire onto the mounting plate in the enclosure. If you get a reading now (when the Raise button is pressed), the fault will almost certainly be with one of the door contacts. If you still get no reading, go to step 2.
   2. Hold one probe on the top terminal of the contactor (with the orange wire) and the other one on the pink wire coming from one of the fuse-holders. If you get a circuit here, move the probe up to the input side, then the output side of the key switch, then to the input side of the Raise switch, to identify the point the circuit is being blocked.