The plant air system has two parts. One is a large compressor system driven by a single 400-hp motor. The other is a small compressor that keeps the large system from short-cycling in response to minor pressure drops. Several months ago, an inquiry from the plant manager resulted in replacing the 400-hp motor with an energy-efficient motor. The original had been in service for a long time, so part of the justification was that a new motor would prevent an unplanned system failure. That part was fine, but the plant controller says the expected energy savings did not materialize. Now the plant manager wants you to evaluate the motor for efficiency. What should you do?
This kind of thing sometimes happens with energy projects: They are comparing apples and oranges. Yes, check the motor nameplate and ensure it’s the correct model. Then do the real work of identifying the energy leaks in that system.
Is the new motor properly aligned? Has a vibration analysis been done? Is operations using more air now due to a process change or increased output? Has someone performed ultrasonic inspection on the air distribution system, or have those leaks gotten worse since the motor change? Was there a motor supply power quality analysis before and after the replacement? Is the new motor power factor corrected?
