Troubleshooting a DC Brushed Motor

Owned by Corey Boyles
Last updated: Aug 06, 2024 by Eric Rojas (Unlicensed)
2 min read

All testing listed here should be done under SAFE conditions, meaning all power has been removed from the drive and the motor is in a safe (stopped) state. 

 

Field Winding   

  1. Measure resistance across the field leads (including any cabling between the drive and motor).  Disconnect the field leads from the drive before this measurement is made.  Compare your reading to the motor's nameplate value for the field resistance.  (if not noted in the motor specs, use Ohm's law to calculate how much the resistance should be, R = Field Voltage Rating / Field Current Rating)

  1. Megger test the field to ground and field to armature to look for insulation failure that could lead to leakage currents

Possible 590+ drive alarms that might be caused by field winding issues include:  FIELD FAIL, FIELD OVER I, STALL TRIP, SPEED FEEDBACK, OVERSPEED

  

Armature Winding

  1. Visually inspect the commutator ring - carmel colored, even spacing between the bars, no grooves

  1. Visually inspect the brushes and bush holders - firmly in place, not touching the armature, brushes not too short, not excessive carbon dust build-up.  Also verify you are using the recommended brushes for your particular motor.

  1. Megger test the armature leads to ground and to the field to look for insulation failure that could lead to leakage currents (include any cabling involved).  Disconnect the armature leads from the drive before this measurement is made.

Possible 590+ drive alarms that might be caused by armature issues include:  OVER VOLTS (VA), OVER I TRIP, STALL TRIP, SPEED FEEDBACK, OVERSPEED

  

Thermostat (if equipped and used)

  1. Measure the resistance across the thermostat leads.  At normal temperatures, most thermostats are normally closed contacts that should measure close to 0 ohms.

Possible 590+ drive alarms that might be caused by thermostat issues include:  THERMISTOR

 

 

 

 

 

 

glh   6/2021