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The repair decision does not rest on a single criterion; which part has failed, the motor's power and history, whether parts can be found and how long the machine can wait are all weighed together. For small motors replacement, and for large motors a well-executed repair, usually turns out to be the more sensible choice.
First leaning by type of failure
| Failure | Leaning to repair | Leaning to replace |
|---|---|---|
| Bearing, seal, fan or fan cover | Strong | Weak |
| Burnt winding | Clear for large ratings | Clear for small ratings |
| Broken shaft | If the shaft can be machined | If the rotor is damaged too |
| Cracked frame or foot | Rarely | In most cases |
Other factors that change the decision
- Rewind history: In a motor rewound several times, the lamination stack may have been affected by heat; the motor runs hotter and its values may drift from the nameplate.
- Parts availability: On old or non-standard frames, end shields, fans and bearing seats can be a problem.
- Cost of downtime: If the repair would sit in the workshop longer than a new motor's lead time and the machine is holding up production, replacement comes to the fore.
- Running hours: On a machine that runs long hours all year, the operating cost of a current motor should also be counted; you can make that comparison with your own data using the energy consumption calculator.
What to ask for in a repair quote
Ask the workshop not just for a price but for the scope of the work: which bearings will be changed, which insulation class the rewind will use, which measurements will be reported after repair, and what guarantee the workshop gives. This information lets you genuinely compare a repaired motor with a new one.
The cause of the failure comes first either way
Whichever route is chosen, the outcome will not change unless the supply, load or mounting problem behind the failure is removed.
If you decide to replace, you can look for models matching the old motor's power and speed in the three-phase motor shop and on the three-phase induction motors page.