# Motor Efficiency

Discussion in 'Homework Help' started by Prototape, Apr 6, 2011.

1. ### Prototape Thread Starter New Member

Feb 12, 2011
10
0
I'm stuck on a problem regarding motor efficiency. My text doesn't give me any sort of formula, nor does it even begin to tell me how to start. I've looked on the internet, but they all have a bunch of variables that I don't need in my equation.

So here's the question:

An AC motor draws 5.5 amperes of current at 120 VRMS while driving a 3/4 HP load. What is the efficiency of the motor?

I'm not looking for someone to give me a straight out answer to my homework, I just need an equation to plug this into.
Thank you.

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
If you know the formula for power (P = I * E), you can figure the power consumed by the motor. If you know the electrical equivalent of one horsepower (in watts), you can see if there is a discrepancy between the two figures.

3. ### Prototape Thread Starter New Member

Feb 12, 2011
10
0
Got it, thank you very much!