Induction Motors – Fault Findings and Remedies
| Faults | Symptons | Possible Causes |
Remedies |
|---|---|---|---|
| Fail to start without load | Motionless & soundless | Power-off | Consult power company |
| Switch-off | Switch-on | ||
| No-fuse | Install fuse | ||
| Broken wiring | Check wiring and repair | ||
| Broken lead | Check wiring and repair | ||
| Broken windings | Check windings and repair | ||
| Fuse blows (Automatic switch trips off, slow start with electro-magnetic noise) |
Short circuit of circuit switches | Check circuit switches and replace | |
| Incorrect wiring | Check wiring according to nameplate | ||
| Poor contact at terminals | Lock tightly | ||
| Windings grounded | Factory repair | ||
| Broken windings | Factory repair | ||
| Poor contact of circuit switches | Check and repair | ||
| Broken wiring | Check and repair | ||
| Poor contact of starting switches | Check and repair | ||
| Short circuit of starting switches | Check and repair | ||
| Incorrect connections of starting switches | Connect according to nameplate | ||
| Loading after start | Fuse blows (Fail to restart due to trip-off of automatic switch) |
Insufficient capacity of fuse | Replace fuse if wiring permits |
| Overload | Lighten load | ||
| High load at low voltage | Check circuit capacity and reduce load | ||
| Motor overheats | Overload or intermittent overload | Lighten load | |
| Under-voltage | Check circuit capacity and power source | ||
| Over-voltage | Check power source | ||
| Ventilation duct clogged | Remove the foreign matter in the duct | ||
| Ambient temperature exceeds 40°C | Correct insulation class to B or F, or lower ambient temperature. | ||
| Friction between rotor and stator | Factory repair | ||
| Fuse blown (Single-phase rotating) | Install the specified fuse | ||
| Poor contact of circuit switches | Check and repair | ||
| Poor contact of circuit starting switches | Check and repair | ||
| Unbalanced three-phase voltage | Check circuit or consult power company | ||
| Speed falls sharply | Voltage drops | Check circuit and power source | |
| Sudden overload | Check machine | ||
| Single-phase rotating | Check circuit and repair | ||
| Switch overheats | Insufficient capacity of switch | Replace switch | |
| High load | Lighten load | ||
| Bearing overheats | High belt tension | Adjust belt tension | |
| Slack belt tension | Adjust belt tension | ||
| Misalignment between motor and machine shafts | Re-align | ||
| Over speed of bearing outer-ring | Adjust bracket | ||
| High bearing noise | Replace the damaged bearing | ||
| Noise | Electro-magnetic noise induced by electricity | Occurrence from its first operation | Could be normal |
| Sudden sharp noise and smoky | Short circuit of windings Factory repair |
||
| Bearing noise | Noise of low “Shi-Shi” or “Thru-Thru” | Could be normal | |
| “Kala-Kala” as result of poor lubrication | Grease | ||
| “Kulo-Kulo” as a result of deteriorated grease | Clean bearing and grease | ||
| “Sa-Sa” or larger noise | Replace the damaged bearing | ||
| Mechanical noise caused by machinery | Loose belt sheave | Adjust key and lock the screw | |
| Loose coupling | Adjust the position of couplings, lock key and screw | ||
| Loose screw on fan cover | Lock fan cover screw tightly | ||
| Fan rubbing | Adjust fan position | ||
| Rubbing as a result of ingression of foreign materials | Clean motor interior and ventilation ducts | ||
| Wind noise | Noise induced by air flowing through ventilation ducts | ||
| Induced by conveyance machine | Repair machine | ||
| Vibration | Electro-magnetic vibration | Short circuit of windings | Factory repair |
| Open circuit of rotor | Factory repair | ||
| Mechanical vibration | Unbalanced rotor | Factory repair | |
| Unbalanced fan | Factory repair | ||
| Broken fan blade | Replace fan | ||
| Unsymmetrical centers between belt sheaves | Align central points | ||
| Central points of couplings do not lie on the same level | Adjust the central points of couplings to the same level | ||
| Improper mounting installation | Lock the mounting screws | ||
| Motor mounting bed is not strong enough | Reinforce mounting bed | ||
| Mounting bed vibration caused by machines near motor | Eliminate the vibration source near motor |
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| Remarks: (1) Circuit switches: These include knife switches, electromagnetic switches, fuse and other connection switch etc. (2) Starting switches: These include Delta-Star starters, compensate starters, reactance starters, resistor starters, starting controllers etc. | |||