|
Motor problems can be mechanical, electrical, thermal, or magnetic:
- Voltage loss – Check output at supply and at the motor terminals.
- Overcurrent Draw – Check current to motor with ammeter with the load attached to the motor.
- Insulation Breakdown – Test windings with a megohm-meter (meggar). Insulation breakdown can be caused by heat or chemicals in the atmosphere. The megohm-meter produces a high voltage and looks for low resistance levels.
- Shorts and Opens – Shorts can be detected by measuring resistance levels across the winding terminals of the stator with a simple multi-meter.
A short will be indicated by a zero or low resistance reading. Shorts in motor armatures can be detected through the use of a growler which produces a magnetic field in which the armature is placed. A soft iron feeler (hacksaw blade etc.) is held along a slot opposite the side of the coil spanned by the unit. The blade will stick and vibrate if a short exists in the armature. Opens can be detected in armatures using a growler by shorting the adjacent coils spanning the unit. A good coil will produce sparks and a bad one will not. For shorts in motor commutators place a voltage source across the commutator bars; sparks indicate the presence of a short.
|
