How to use a multimeter to detect the cause of air circuit breaker tripping
Short circuits do not require measurement, and there are obvious or even huge acoustic, optical, and electrical phenomena. If the trip is caused by this reason, as long as the cause of the short circuit is eliminated, check whether the contacts of the air switch have been burned by the short circuit current. Disconnect the upper power supply to make the air switch in an absolutely non charged state, close the air switch, and measure the three-phase incoming and outgoing wiring terminals of this switch with a multimeter ohm range. If the conductivity is good, you can try it out by powering it on. If there is a phase loss, there is no need to say more, replace the air switch.
There is a possibility of breakdown in the wiring terminals of an air switch that has experienced a short circuit. The insulation resistance between each wiring terminal can be measured using a megohmmeter (or by using a multimeter with a gear of 20K or higher and removing the incoming and outgoing wires on both sides of the air switch). If the pointer of the shaking meter quickly deflects to the right at the beginning of shaking, it indicates that the phase 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 tested by powering on.
The procedure for power on trial is as described earlier. Disconnect the front power supply, close the air switch that has been repaired, and then close the front power 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 trips due to overload with your hand usually makes you feel that the housing is quite hot, even hot to the touch. This will cause the internal thermal components of the air switch to produce protective actions.
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 air switch should be replaced according to the actual working current.
Wrong action. When the inlet and outlet wires of the air switch are aluminum wires, it is easy to undergo oxidation reaction with the copper terminal of the air switch, causing heating at the terminal. The thermal protection device inside the air switch is deformed by heat, resulting in protective action. This is a typical misoperation. 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.
