To really understand how to calculate the power factor or efficiency of any motor you must understand the difference between true power and apparent power.
True Power = power used to do useful work.
Apparent Power = power with the potential to do work-but no ability to do useful work independently.
Calculate True Power:
Since 1 hp is equal to 746 watts multiplying the horsepower of a motor by 746 watts will yield true power whether the system in question is single or three phase.
True Power (Output Power) = 746 watts x Hp Rating
Calculate Apparent Power:
Single-Phase Apparent Power (Input Power) = E x I (Voltage x Current)
Calculate Motor Efficiency:
What is the efficiency of a 5 hp. 230-volt single-phase A.C. motor with a f.l.c. of 28 amps?
True Power = 5 hp x 746 watts = 3,730 watts
Apparent Power = 230 volts x 28 amps = 6440 volt-amps
Efficiency = 3,730 watts/6440 volt-amps = .579 or 57.9%
To answer an exam question correctly you need to understand the theory behind the question. We’ll help you to grasp the concepts and develop the test taking skills that will help you to pass the electrical exam. Preparation is the key to success!
Call 888-919-3926 or click the “Register Now” tab to start preparing to pass your exam today.