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Low-resistance fields in DC motors; application and testing

  • September 2018
  • Number of views: 8827
  • Article rating: 5.0

Chase Fell
Precision Coil and Rotor

Ground faults, short circuits and bad connections in interpole coils, series coils and compensating windings cause performance problems in DC machines, including brush sparking, flashover, stalling and catastrophic failure. Shunt coils have many turns of relatively small wire and are usually excited by a DC source independent of the armature. Series, interpole and compensating coils in the armature circuit usually are wound with a few turns of heavy wire as these coils carry armature current.

For accurate test results, make sure windings are clean and dry. Verify connections of low resistance fields by visual inspection. Apply DC voltage to an assembled field frame and perform a thermography scan to detect problems including uneven heating and loose or corroded connections. Verify that the terminal lead markings are correct. Lead marking should conform to the original equipment manufacturer (OEM) nameplate, NEMA MG1 or IEC 60034-8, whichever is applicable.

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AVAILABLE IN SPANISH

ANSI/EASA AR100

More information on this topic can be found in ANSI/EASA AR100
  • Section 4: Testing

EASA Technical Manual

More information on this topic can be found in EASA's Technical Manual
  • Section 3: DC Machines

Related Reference and Training Materials

Fundamentals of DC Motors & Operation Tips
  • Section 4: Testing
  • Section 7: Frames
  • Section 9: Motor Assembly & Final Testing

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Tags: DC Brushes Interpoles Stabilized shunt Compound DC machines
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