How to use a multimeter to detect the cause of air switch tripping
There are usually three reasons for air switch tripping. Short circuit, overload, and malfunction.
There is no need to measure short circuits, and there are obvious or even huge acoustic and optoelectronic phenomena. For tripping caused by this reason, as long as the cause of the short circuit is eliminated, check whether the contact of the air switch has been burned by the short circuit current. Disconnect the superior power supply to ensure that the air switch is in an absolutely dead state. Close the air switch and measure the three-phase incoming and outgoing wiring terminals of the switch using a multimeter's ohm range. If the conductivity is good, you can power on and try it out. If the phase is missing, there is no need to say more. Replace the air switch.
If a short circuit occurs in the air switch, there is a possibility of the terminal being broken down. You can use a megger to measure the insulation resistance between each terminal (or use a multimeter to measure at a gear of 20K or higher, and remove the incoming and outgoing wires on both sides of the air switch). If the pointer of the dial indicator quickly deflects to the right at the beginning of shaking, it indicates that the interphase insulation of the air switch has been broken down and cannot be used anymore. If the insulation resistance is high, several megaohms or more, it can be powered on for trial use.
The procedure for powering on the trial is as described earlier. Disconnect the previous power supply, close the air switch that has been repaired, and then close the previous power supply switch. If the power supply is normal and there are no abnormal sounds or odors, the air switch can continue to be used.
Overload. Overload is one of the reasons for frequent tripping of air switches. Touching the air switch that is overloaded and tripped with your hand usually makes you feel that the shell is relatively hot, or even hot to the touch. This will cause a protective action on the thermal components inside the air switch.
Measure the working current of the air switch using the AC current range of a multimeter. If the working current exceeds the rated current of the air switch and continues to operate, a higher level of air switch should be replaced based on the actual working current.
Misoperation. When the inlet and outlet wires of the air switch are aluminum wires, it is easy to react with the copper terminal blocks of the air switch, causing heat at the terminal blocks. The thermal protection device inside the air switch is deformed due to heat, resulting in a protective action. This is a typical malfunction. As long as copper aluminum terminal blocks are pressed onto the aluminum wire and tightly combined with the air switch terminal blocks, this problem can be solved.
