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If motors on the same machine fail at short intervals, it is not the motor that keeps changing but the conditions that stay in place. Look for the cause under one of these headings: supply, machine load, mounting arrangement, environment or operating pattern. Recording the type of every failure reveals which of these is responsible.
The type of failure points the way
| Recurring finding | Where to look |
|---|---|
| The bearing on the same side always fails | Belt tension, pulley position, coupling alignment |
| The whole winding overheats and darkens | Overload, frequent starts, cooling air |
| One phase coil burns | Supply balance, contactor contacts, terminal tightness |
| Shaft or foot cracks | Base rigidity, vibration, shock load |
| Moisture or rust in the terminal box | Washdown, condensation, direction of cable entry |
Causes that get overlooked
- Change in operating pattern: More shifts, or automation making the machine stop and start often.
- Product change: A switch to denser, wetter or harder material.
- Maintenance habits: Too much or incompatible grease pumped into the bearing, fan cover not cleaned.
- Rewind quality: If earlier motors were rewound and refitted, the failure may have come from the motor itself.
- Wrong selection: The machine's real load may be above the power of the motor fitted.
How to keep a fault log
For every failure, write down the date, running hours, type of failure, the product and weather at the time, the current drawn by the motor and the action taken. Once a few records sit side by side, the common factor often shows itself: only in the summer months, only with a particular product, or only on one shift.
Once the cause is found
Every new motor fitted before the root cause is removed is also a risk from a warranty point of view; overload, phase imbalance and poor ventilation are among the conditions not covered. After solving the cause, review the machine's real requirement with the motor selection wizard and find a suitable model in the three-phase motor shop.