The use of a multimeter to determine the cause of a circuit breaker trip
There are usually three reasons why an air switch trips. Short circuit, overload and malfunction.
There is no need to measure the short circuit, and there will be obvious or even huge acousto-optical phenomena. For tripping caused by this reason, just eliminate the cause of the short circuit and then check whether the contacts of the air switch have been burned by the short-circuit current. Disconnect the superior power supply so that the air switch is in an absolutely non-energized state. Close the air switch and use the ohm range of a multimeter to measure the three-phase incoming and outgoing wire terminals of the switch. If the continuity is good, you can power on and try it out. If the phase is missing, needless to say, replace the air switch.
If a short circuit occurs in the air switch, the terminals may be broken down. You can use a megger to measure the insulation resistance between the terminals (you can also use a multimeter with a range of 20K or above to measure it. Remove the insulators on both sides of the air switch. wires and outgoing wires). If the pointer of the rocker quickly deflects to the right as soon as you start shaking the watch, it means that the phase insulation of the air switch has been broken down and cannot be used. If the insulation resistance is very large, several megohms or more, you can power on and try it out.
The power-on trial procedure is as mentioned above. Disconnect the front-end power supply, close the repaired air switch, and then close the front-end power switch. If the power supply is normal and there are no abnormal sounds or smells, the air switch can continue to be used. .
overload. Overload is one of the reasons for frequent air switch tripping. If you touch the overload tripped air switch with your hand, you will usually feel that the shell is hot, even hot to the touch. This will cause the thermal element inside the air switch to take protective action.
Use the AC current range of a multimeter to measure the operating current of the air switch. If the operating current exceeds the rated current of the air switch and continues to operate, the air switch should be replaced with a larger level one based on the actual operating current.
Malfunction. When the inlet and outlet wires of the air switch are aluminum wires, they are prone to oxidation reactions with the copper terminals of the air switch, causing heat at the terminals. The thermal protection device inside the air switch is deformed by heat, causing protective action. This is a typical malfunction. This problem can be solved by pressing copper-aluminum terminals on the aluminum wires and tightly combining them with the air switch terminals.
