Motor Efficiency - vs Load

Induction-motor efficiency curve - peaks ~75 % load; drops sharply below 30 %.

MotorEfficiencyLoad

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

\eta(L) \approx \eta_n - k (L - 75)^2

Symbol	Meaning	Unit
$η_n$	Nameplate efficiency	%
$L$	Load %	%

Source: IEC 60034-30-1 IE classes

Induction-motor efficiency curve - peaks ~75 % load; drops sharply below 30 %.