Enter the net output of the shaft (watts) and the net electrical input to the motor (watts) into the calculator to determine the 3 Phase Motor Efficiency. 

3 Phase Motor Efficiency Formula

The following formula is used to calculate the 3 Phase Motor Efficiency. 

E3p = NO / NI *100

  • Where E3p is the 3 Phase Motor Efficiency (%)
  • NO is the net output of the shaft (watts) 
  • NI is the net electrical input to the motor (watts) 

How to Calculate 3 Phase Motor Efficiency?

The following two example problems outline how to calculate the 3 Phase Motor Efficiency.

Example Problem #1:

  1. First, determine the net output of the shaft (watts). In this example, the net output of the shaft (watts) is given as 500.
  2. Next, determine the net electrical input to the motor (watts). For this problem, the net electrical input to the motor (watts) is given as 2000.
  3. Finally, calculate the 3 Phase Motor Efficiency using the equation above: 

E3p = NO / NI *100

Inserting the values from above and solving the equation: 

E3p = 500 /2000 *100 = 25 (%)

Example Problem #2: 

Using the same process as above, first define the variables required by the formula. In this case, these values are:

net output of the shaft (watts) = 13

net electrical input to the motor (watts) = 82

Entering these values yields:

E3p = 13 / 82 *100 = 15.85 (%)