Motor Efficiency

Motor efficiency, abbreviated as \(\eta_m\) (Greek symbol eta), a dimensionless number, is the ratio of shaft power power out and electric power input of a motor.

 

 Motor Efficiency formula

\(\large{ \eta_m = \frac{ 0.7457 \; HP \; Load  }{ P_{in} } }\)

Where:

Units	English	Metric
\(\large{ \eta_m }\)  (Greek symbol eta) = motor efficiency	\(\large{dimensionless}\)
\(\large{ P_{in} }\) = input power	\(\large{\frac{ft-lbf}{sec}}\)	\(\large{kg\;m^2\;s^{-3}}\)
\(\large{ HP }\) = horsepower	\(\large{\frac{ft-lbf}{sec}}\)	\(\large{\frac{Btu}{s}}\)
\(\large{ Load }\) = output power as a % of rated power	\(\large{dimensionless}\)