When the inlet/unloader valve is open, the air enters the compressor screw element. The screw element works like a pump and it compressed the air. During this process, oil is injected in the element. The oil is there to cool the air, as the air gets very hot during compression.
[pdf] Check the isolation of the motor windings. Should be in the mage-ohms (you need an isolation tester / high voltage ohm meter for this). Check the voltage when the compressor is running. If the voltage drop significantly when the compressor starts/runs, you have a bad connection somewhere.
[pdf] The Variable Frequency Rotary Screw Air Compressor is an energy efficient solution for industrial air compression requirements. The motor output frequency is intelligently matched to air consumption, making it more energy efficient and longer lasting than traditional air compressors.
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