| Failure |
Probable Cause |
Corrective Measures |
| Motor Fails to Start |
- No voltage supply
- Low voltage supply
- Wrong control connections
- Loose connection at some terminal lug
- Overload
- Brushes
|
- Check feed connections to control system and from this to motor
- Check voltage supply and ascertain that voltage remains within 10% of the rated voltage shown on the motor nameplate
- Compare connections with the wiring diagram on the motor nameplate
- Tighten all connections
- Try to start motor under no-load conditions. If it starts, there may be an overload condition or a blocking of the starting mechanism. Reduce load to rated load level and increase torque.
- Brushes may be worn, dirty or incorrectly fitted.
|
| High Noise Level |
- Unbalance
- Distorted shaft
- Incorrect alignment
- Uneven air gap
- Dirt in the air gap
- Extraneous matter stuck between fan and motor casing
- Loose motor foundation
- Worn bearing.
|
- Vibrations can be eliminated by balancing rotor. If load is coupled
directly to motor shaft, the load can be unbalanced.
- Shaft can be bent, check rotor balance and eccentricity
- Check motor alignment with machine running
- Check shaft for warping or bearing wear
- Dismantle motor and remove dirt or dust with jet of dry air
- Dismantle motor and clean. Remove trash or debris from motor vicinity
- Tighten all foundation studs. If necessary, realign motor
- Check lubrication. Replace bearing if noise is excessive and continuous
|
| Overheating of Bearings |
- Excessive grease
- Excessive axial or radial strain on belt
- Deformed shaft
- Rough bearing surface
- Loose or poorly fitted motor end shields
- Lack of grease
- Hardened grease causing locking of balls
- Foreign material in grease
|
- Remove grease bleeder plug and run motor until excess grease is expelled
- Reduce belt tension
- Have shaft straightened and check rotor balance
- Replace bearings before they damage shaft
- Check end shields for close fit around circumference and tightness
- Add grease to bearing
- Replace bearings
- Flush out housings and relubricate.
|
| Intense Bearing Vibration |
- Unbalanced rotor
- Dirty or worn bearing
- Bearing rings too tight on shaft and /or bearing housing
- Extraneous solid particles in bearing
|
- Balance rotor statically and dynamically.
- If bearing rings are in perfect condition, clean and relubricate the
bearing, otherwise, replace bearing.
- Before altering shaft or housing dimensions, it is advisable to ascertain
that bearing dimensions correspond to manufacturer's specification
- Take bearing apart and clean. Reassemble only if rotating and support
surfaces are unharmed.
|
| Overheating of Motor |
- Obstructed cooling system
- Overload
- Incorrect voltages and frequencies
- Frequent inversion
- Rotor dragging on stator
- Unbalanced electrical load (burnt fuse, incorrect control)
|
- Clean and dry motor; inspect air vents and windings periodically
- Check application, measuring voltage and current under normal running
conditions
- Compare values on motor nameplate with those of mains supply. Also check
voltage at motor terminals under full load.
- Exchange motor for another that meets needs.
- Check bearing wear and shaft curvature.
- Check for unbalanced voltages or operation under single-phase condition.
|