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We have a 180 V dc permanent magnet motor.

When engaging the control board while the motor is hooked up. The output to motor drops out and reads no voltage. If I take the motor leads off the board and fire the controller the outputs will read 180 V just like it's supposed too. So when the motor is hooked up to the board we get 0 V, when it's not we get the 180 V that is intended. We have tried switching out the board and also the motor and still get the same outcome.This current setup has ran perfectly fine for the last 20 years. Three days ago this problem occurred. The wires from the board going to the motor are fine. Nothing has changed as this is not a new setup.

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    \$\begingroup\$ This really should be in an industrial maintenance group -- this group is supposed to be for design questions. At a (I claim very educated) guess you're overloading the board, and tripping some on-board overcurrent protection. Either the motor is bigger than the board wants, there's a fault in the wiring to the motor, the motor is broken, the board is broken, or the motor is loaded too heavily for the current the board can supply. \$\endgroup\$ – TimWescott Apr 25 at 15:30
  • \$\begingroup\$ It would help a lot if you edit the question to say if this is a new installation, or if it worked before, what has changed. \$\endgroup\$ – TimWescott Apr 25 at 15:30
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    \$\begingroup\$ So the electronics haven't changed, and the motor hasn't changed. Has the load on the motor changed? Does it turn less freely than before? How soon does the board turn off? Has the power to the board changed? Is it getting voltage over or under what it used to? \$\endgroup\$ – TimWescott Apr 25 at 16:40
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    \$\begingroup\$ Have you checked the motor wiring? Does the controller consist of a single board? Is the input to the board single-phase or three-phase? What is connected to the board besides the power and the motor? Are there any wired-in meters, lights etc? \$\endgroup\$ – Charles Cowie Apr 25 at 17:44
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    \$\begingroup\$ If you know what the motor winding resistance should be/used to be, I would measure it now and see if it has changed. The fact that you get 0V suggests -- if anything -- that it may be quite low (i.e. there may be a short in the windings, or elsewhere) \$\endgroup\$ – Jeff McBride Apr 25 at 18:07

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