Deciding to rewind or replace a failed motor
The rewind-versus-replace decision weighs repairing a failed electric motor against buying a new high-efficiency one, accounting for the small efficiency loss a rewind often introduces and the running hours over which any difference compounds. For a motor that runs many hours a year, replacement with a premium-efficiency unit frequently beats rewinding on lifetime cost.
What it is
When a motor burns out, the immediate choice is to rewind it — strip and replace its windings — or scrap it and fit a new one. A rewind is cheaper up front but can shave a little efficiency if done with poor process control, and the old motor's efficiency may already lag modern classes. The decision balances repair cost, the efficiency difference, and how many hours the motor runs.
Why it is done
Because a motor's electricity cost over its life dwarfs its purchase price, even a small efficiency difference matters on a machine that runs continuously. A cheap rewind that loses efficiency can cost more in energy than a new motor would have saved. Treating the choice as a lifetime-cost decision, not a repair-bill decision, often justifies replacement on heavily used motors and rewinding only on lightly used or large special ones.
How it is done
The motor's running hours, load and existing efficiency class are established, and the cost of a quality rewind is compared with a new premium-efficiency motor of the same rating. The lifetime energy cost of each option is estimated over the expected remaining service, and any rewind shop is checked for controlled processes that preserve efficiency. The lower lifetime-cost option is chosen, with replacement favoured for high-hours motors and rewinding for lightly used or non-standard ones.
- Establish hours & load
- Check existing efficiency
- Cost rewind vs new
- Estimate lifetime energy
- Verify rewind quality
- Choose lowest lifetime cost
What to watch for
Defaulting to rewind because the invoice is smaller ignores the energy cost that dominates a high-hours motor's life. Using an uncontrolled rewind shop that overheats the core during burnout degrades efficiency further, quietly raising running cost.
Related practices
Running a compressed-air leak survey programme
Retrofitting waste-heat recovery
Retrofitting variable-speed drives
Related topics
Motor Efficiency and IE Classes Explained · Specific Energy Consumption (SEC) · Total Cost of Ownership (TCO) · VFD (Variable Frequency Drive)
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