Motor Efficiency calculation

In my industry i have induction motors which are aged more than 15 years,many of them were re wounded around 2-3 times. i am facing more problems with their performance

Now i just want to know at what efficiency they are and how much percentage of efficiency i lost.

i want to implement this efficiency calculation practically.

can any one tell me some calculating methods and what parameters should i take and calculation formulas etc???

 

Hi,

When a motor burns out, the obvious best approach is to rewind the motor. If the magnetic core of a failed motor is undamaged and appropriate procedures are followed, a rewound motor will retain its original efficiency.

On the other hand, those times when a motor has failed are also opportunities to upgrade motor efficiency. Especially if the failed motor is 10 or more years old — perhaps with unknown efficiency, and possibly having been improperly rewound in the past.

You can read about a study on the effects of repair on motor efficiency "here("")":http://www.slideshare.net/BDRIndonesia/the-effect-of-repair-on-motor-efficiency

Hi Kevin,
thank you for the information.

can you tell me how to calculate a motor efficiency in practical?

Hi,

In general, efficiency is just the factor of the output power over the input power.

η = (output power)/(input power)

for more equation on motors, you can check this out: http://www.cse.iitk.ac.in/users/amit/universal-motor.html

Electrical motor efficiency is the ratio between shaft output power - and electrical input power.

If power output is measured in Watt (W), efficiency can be expressed as:

ηm = Pout / Pin (1)

where

ηm = motor efficiency

Pout = shaft power out (Watt, W)

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