Common Motor Failures And Causes

What do a broken razor, car and washing machine have in common? Let’s get you there quickly: they all have a bad motor. So why would your razor, car and washing machines break down in the first place? This article has some answers for your question.

Problem 1: unable to start

Possible reasons:

  • No voltage for motor power supply
  • Motor power cord disconnected or joint loosening
  • Armature winding open
  • Poor contact between the brush and the commutator
  • Motor power switch damaged or poor contact
  • The armature is stuck

Problem 2: slow speed

Possible reasons:

  • Brush winding grounding
  • Armature winding has short circuit elements
  • Severely worn-out brush causes poor contact between the brush and commutator as well as small pressure of the brush spring
  • Bearing wear or lack lubricating oil
  • Low power supply voltage, or use the dry battery for too long a time

Problem 3: too fast speed

Possible reasons:

  • Too high power supply voltage
  • Weakened stator magnetic field
  • Too light motor load

Problem 4: electriferous case

Possible reasons:

  • Armature winding grounding
  • The stator excitation winding grounding
  • The commutator grounding
  • The brush rod grounding
  • The brush holder of the commutation device grounding

Problem 5: brush throwing excessive sparks

Possible reasons:

  • The brush is not located on the neutral line
  • Too small a contact surface between brush and commutator, and too high current density
  • Short circuit between commutators
  • Severely uneven commutator surface
  • Uneven mica between the commutators
  • Impure brush material, with hard crumbs or other impurities
  • Brush holder grounding
  • Brush winding grounding
  • Short circuit of brush winding
  • Reverse connection of brush winding


Problem 6: the commutator produces sparks

Possible reasons:

  • The brush is far away from the neutral line
  • The commutator is seriously uneven, which makes poor contact between the brush and the commutator
  • Excessive potential difference between commutator
  • Serious break or short circuit of armature winding
  • Armature winding grounding
  • Too high voltage or rotating speed of motor

Problem 7: fail to start every time

Possible reasons:

  • The armature winding has circuit breaking units
  • Poor contact of the power switch
  • Too large commutator ovality and too short brushes

Problem 8: crash sound when running

Possible reasons:

  • Bending of motor rotor
  • The armature slot wedge protruding
  • The armature winding end touches the casing
  • The bearing is damaged, causing the armature broom

Problem 9: the armature hisses loudly

Possible reasons:

  • Too hard brush
  • Too high pressure of brush springs


Problem 10: fuse burnt when loaded

Possible reasons:

  • Over-voltage of motor power supply
  • Brush is not located on neutral line
  • Short circuit of armature winding or excitation winding

Problem 11: fuse burnt when no-load

Possible reasons:

  • The armature winding is severely broken
  • The armature winding severely grounding
  • The brush holder grounding
  • The motor bearing is too tight
  • The excitation winding is severely shorted
  • The brush away from the neutral position

Problem 12: the brush rattles

Possible reasons:

  • Uneven mica between the commutators
  • Uneven commutator piece
  • Wrong brush size specifications
  • Large bearing clearance

Problem 13: casing heated

Possible reasons:

  • No good heat dissipation and the armature winding is damped severely
  • Long-term overload operation
  • Bad lubrication of bearings

Problem 14: armature winding fever

Possible reasons:

  • Serious dampness of armature winding
  • Serious motor overload
  • Short circuit unit of armature winding

Have you experienced other problems about DC motor? Feel free to contact us or leave a comment. We’d be glad to hear from you and help you.

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