The air compressor kept reporting a phase missing fault, and it was normal at irregular intervals. It turned out to be the cause!
Air compressor phase loss troubleshooting
I received an equipment defect notice today. An air compressor kept reporting missing phase and shutting down. My colleague said that this fault had occurred before, but the cause was not found. It was inexplicable.
Go to the scene and take a look. This is an air compressor with five red rings, and the alarm message is still there – “B phase is missing and shut down.” Open the electrical control box and check the three-phase input voltage. The voltage of one phase measured from the power input terminal is low, only 90V to ground, and the other two phases are normal. Find the power switch of this air compressor and measure that the incoming line voltage of the switch is normal and the outlet line A is 90V relative to ground. It can be seen that the power switch has an internal fault. After replacing the switch, the three-phase voltage is normal and the test machine is normal.
In plastic case circuit breakers, after a long time, poor contact occurs in the internal dynamic and static contacts, which increases the contact resistance, or the crimping screws are tightened too loosely, causing overheating and ablation of the internal connecting wires, which will also lead to a reduction in the outlet voltage or even no voltage.
The internal fault of this kind of molded case circuit breaker is progressive and highly concealed. Sometimes the fault phenomenon will suddenly disappear due to re-opening and closing. This is why this air compressor had the same problem before, but it did not Find out the cause of the fault.