To Calculate Efficiency of Loaded Induction Motor

Never did it with an electric motor but certainly did with an old 4 cylinder petrol engine in the thermodynamics lab seemingly 200 years ago.

You have the values of the energy contained in the fuel and you can meter the amount of fuel used. With your motor you have much the same with volts and amps which you can measure.

Your losses will be as heat with some minimal audio and vibration. Now devise a method to measure your heat losses. As nothing gets lost or used up the heat losses are your in efficiency.

See this link, it may help you, how to do calculation

Induction motor calculation

You might want to look it up on the manufacturer's data sheet for the motor, Boss, if the calculation method doesn't work?

As lyn has stated before, calculating efficiency is simple: (output power / input power) *100%. Knowing current and voltage without the phase angle, you still don't know the input power. There's the little matter of power factor. Nevertheless, watt meters are pretty straight forward, so you can readily find the input power. The trick is measuring the output power. Unless the motor is driving a dynamometer or has a torque measuring coupling, you really can't. I suppose you could put the motor in an insulated box with a circulating air system and measure the heat removal required to maintain constant temperature? If the motor is driving a pump and you know the pressure differential and flow rate, you could calculate an overall electric-to-fluid efficiency, but you wouldn't know the breakdown of efficiency between the motor and pump.

Measure the RPM with a Prony brake load in place and calculate from there.

www.engineeringtoolbox.com/electrical-​motor-efficiency-d...

Quite a few contributors have given links to sites with tables and suggestions. I'm not convinced any of these can work in this instance. Problem using tables etc is that you need to assume the motor is fully loaded i.e. a 5.5kW is flat out. Often our mechanical friends over spec the motor requirement so that the motor we supply is over spec-ced and running inefficiently.

You can measure all of the electrical inputs, V, A, pF etc so you know kW input. Working out a random connected load is difficult. Generally you would have to put a known load onto the motor such as a brake.

With your random load - conveyor, pump, hoist, fan etc there will be losses in the mechanical part of the system. Somehow you need to tie something down so that you can measure it.