Electric Motor Efficiency

Interview Question: What is the Efficiency in Electric motor ?

 

Answer:

Power
(hp)         Minimum Nominal Efficiency1) 
1 - 4        78.8 
5 - 9         84.0 
10 - 19      85.5 
20 - 49      88.5 
50 - 99      90.2 
100 - 124     91.7 
> 125        92.4 
as per NEMA

Electrical motor efficiency is the ratio between the shaft output power - and the electrical input power.Electrical Motor Efficiency when Shaft Output is measured in WattIf power output is measured in Watt (W), efficiency can be expressed as:m = Pout / Pin?

where

m = motor efficiency

Pout = shaft power out (Watt, W)

Pin = electric power in to the motor (Watt, W)

Electrical Motor Efficiency when Shaft Output is measured in Horsepower.