Top Motor Failure Causes and How to Spot Them

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.