Is a 3 phase electric motor more efficient than a single phase motor of equivalent horsepower?

Question

I have an old air conditioner with a 3 phase compressor. Should it's replacement be 3 phase?

Answer 1

Yes 3 phase electric motor is more efficient, less current draw equivalent to a single phase. There are some trade offs. When a single phase unit power drops out, everything shuts down. If a single phase of a three phase motor drops out your motor can go in into thermal runaway. if your motor is running full speed, all of a sudden motor is starving for more power, your windings burn out. So on a three phase you should have a power monitor to automatically shut the system down to prevent a thermal run away.

Answer 2

While John P is partially correct, most modern motor controller have built in fuse links that will shut down the motor for the very cause given, or for over load that causes excessive current draw.

Answer 3

Yes - that's why three phase power is so predominant in industrial and manufacturing plants.