Input, output and losses
η = P_out / P_in × 100%. P_in = √3 × V × I × PF for a balanced three-phase motor.
Losses are the difference between input and output.
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Motor Efficiency Calculator
Efficiency, losses and input power for an electric motor.
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Efficiency = mechanical output / electrical input × 100%.
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Assumptions and limits.
- Steady-state mechanical output and electrical input at the same operating point.
Frequently asked questions
Why does efficiency change with load?
Fixed losses dominate at light load and copper losses rise with current, so efficiency peaks near rated load.