Try to turn the compressor by hand. It should be possible to turn it around. It should turn around smoothly, without any 'hickups' (be sure to completely shut down the air compressor!). Check the isolation of the motor windings.
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[pdf] Either an electrical problem, or the compressor has tripped on a safety device. Check supply power. Check for errors on display. Check emergency stop is out. Check and reset the overload relay. If it’s a new installation, check the phase sequence. Ambient temperature too high or not enough ventilation.
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