The main contactor coil is burnt out

Fault Name: 

The main contactor coil of the lifting machine is burnt out.

Fault Symptom: 

The power on of the all-in-one cannot be run after starting, and the under-voltage fault is reported.

Causes:

Power quality problems occur such as phase loss or low voltage, equipment continuous power, etc.

When the device is not used for a long time, it is necessary to cut off the power supply when it is urgent to prevent the contactor from burning out when the power supply is abnormal. If the software version is upgraded, the software would detect that the MCU board starts to be invalid when the phase loss happens or grid voltage is too low.

Analysis: 

The contactor coil damage is very easy to appear in the low voltage state. Actually, it is verified by the test that when the voltage is lower than 70%, the contactor is directly unstable and the coil is burnt out. In field applications, there is often a phase loss and low grid voltage. The RST front end will have different loads such as electric lights and electric furnaces. If there is a phase loss condition, the input end of the power frequency transformer will be connected in series with some electrical equipment in the field, resulting in the transformer input voltage being lower than the normal voltage, and the transformer output voltage is much lower than the contactor coil. If the device is started at this time, the contactor coil will be unstable, the current will be too large and the heat will damage the coil. At the same time, the load of the low-voltage electrical equipment is too large, and there is a risk that the transformer will be damaged due to excessive current.