Troubleshooting
Trouble | Cause | Remedy |
Motor Will Not Start | Power not available at motor terminals | 1. Check power at starter. Correct any bad connections be- |
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| tween the control apparatus and the motor. |
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| 2. Check starter contacts and control circuit. Reset overloads, |
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| close contacts, reset tripped switches or replace failed con- |
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| trol switches. |
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| 3. If power is not on all leads at starter make sure overload and |
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| short circuit devices are in proper condition. |
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| Wrong connections | Check motor and control connections against wiring diagrams. |
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| Low voltage | Check nameplate voltage against power supply. Check voltage |
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| at motor terminals. |
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| Open circuit in motor winding | Check stator windings for open circuits. |
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| Motor or fan drive stuck | Disconnect motor from load and check motor and Geareducer |
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| for cause of problem. |
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| Rotor defective | Look for broken bars or rings. |
Unusual Motor Noise | Motor running | Stop motor and attempt to start it. Motor will not start if single- |
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| phased. Check wiring, controls and motor. |
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| Motor leads connected incorrectly | Check motor connections against wiring diagram on motor. |
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| Ball bearings | Check lubrication. Replace bade bearings. |
| Electrical unbalance | Check voltages and currents of all three lines. Correct if required. |
| Air gap not uniform | Check and correct bracket fits or bearing. |
| Rotor unbalance | Rebalance. |
| Cooling fan hitting guard | Reinstall or replace fan. |
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Motor Runs Hot | Wrong voltage or unbalanced voltage | Check voltage and current of all three lines against nameplate |
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| values. |
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| Overload | Check fan blade pitch. See Fan Service Manual. Check for drag |
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| in fan drive train as from damaged bearings. |
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| Wrong motor RPM | Check nameplate against power supply. Check RPM of motor |
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| and gear ratio. |
| Bearings overgreased | Remove grease reliefs. Run motor up to speed to purge exces- |
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| sive grease. |
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| Rotor rubs stator bore | If not poor machining, replace worn bearing. |
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| Wrong lubricant in bearings | Change to proper lubricant. See motor manufacturer’s instruc- |
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| tion. |
| One phase open | Stop motor and attempt to start it. Motor will not start if single- |
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| phased. Check wiring, controls and motor. |
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| Poor ventilation | Clean motor and check ventilation openings. Allow ample venti- |
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| lation around motor. |
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| Winding fault | Check with Ohmmeter |
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| Bent motor shaft | Straighten or replace shaft. |
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| Insufficient grease | Remove plugs and regrease bearings. |
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| Deterioration of or foreign material in | Flush bearings and relubricate. |
| grease |
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| Bearings damaged | Replace bearings. |
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| Incorrect fan blade pitch | See Fan Service Manual for blade pitching instructions. |
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Motor Does Not Come Up | Voltage too low at motor terminals be- | Check transformer and setting of taps. Use higher voltage on |
To Speed | cause of line drop | transformer terminals or reduce loads. Increase wire size or |
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| reduce inertia. |
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| Broken rotor bars | Look for cracks near the rings. A new rotor may be required. |
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| Have motor service man check motor. |
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