Energy source conversion

Question

The power input to a motor is 10 kW and the power output is 7 kW. Determine the efficiency of the motor. Can anyone help me? And could you tell me step my step and also answer the same question but both input and output is 25kw thank you

Answer 1

According to [https://www.sciencedirect.com/topics/engineering/motor-efficiency],

A motor with an efficiency of 80% will draw an electrical power of 1/0.8=1.25 kW for each kilowatt of shaft power it delivers.

with shaft power referring to the output mechanical energy, and electrical power referring to the input electrical energy.

In fact, the relationship is linear; P_out = efficiency * P_in, or

efficiency = P_in / P_out

In your case, for part (a):

efficiency = 7 kW / 10 kW = 0.70, or 70%.

for part (b):

efficiency = 25 kW / 25 kW = 1.00, or 100%. This is not possible in the real world, as motors will always have some energy lost as heat due to friction between the shaft and the bearings, and the resistive effects of the wires in the stator and/or rotor.

I hope this helped! If you need more engineering assistance, I recommend checking out my page to see if what I offer is a good match for what you need. Thanks!

Miles