You recently hired on as a senior maintenance electrician at a manufacturing plant. You are actually the only senior maintenance electrician at this plant. The other electricians have far less experience than you do.
After several months of enduring process interruptions due to low pressure in the plant air system, the plant installed another air compressor. They located it on the opposite end of the plant from the existing set of air compressors. This happened a few months before you arrived.
During those few months, the new compressor has shut down on overload many times. Changing various settings on the controls has not solved this problem. The plant engineer has asked you to figure out what is wrong electrically — if anything. How do you approach this?
The distance from its supply may be the problem due to voltage drop. If you look at the relationship between voltage, current, and resistance in the formula for calculating power, you see that as voltage decreases, the motor must draw more current, but it’s squared not linear. Excess voltage drop would cause the motor to overheat.
Measure the voltage at the motor. Is the value acceptable for that motor? If not, then you need a different power distribution scheme (larger conductors would be the usual solution), or you need to relocate the compressor closer to its supply after carefully calculating voltage drop for that new location.
Low power factor is the next most likely culprit, with voltage imbalance closely following. Check the motor lead terminations for conductance, also.
Impress your boss by recommending that ultrasonic imaging be done to locate and repair the leaks that are likely the root cause of the low pressure.
