Electrical test technology exchange meeting and product exhibition

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2023-02-16 09:28

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After removing the cable connecting the sewage pump under the thermal relay, the author used a multimeter and a 500V megohmmeter to test the load cable and the sewage pump, but no abnormality was found! So I had to test the electric control circuit. After measuring the resistance of the multimeter, I found that the electric control circuit was also normal. However, I decided to test the power transmission of the electric control circuit first, but an unexpected scene happened - after the start button was pressed when the air switch was powered on with no load, it still tripped! This made me think that there was a problem with the air switch, and I immediately replaced it with a new air switch of the same model. Unexpectedly, under the no-load test of closing, the air switch still tripped!
Faced with such a situation, I had to take the ultimate skill: throwing electrical devices and cables one by one from the bottom to the top. During the power-on test after disconnecting the thermal relay from the line, the air switch did not trip! Observe again that the six main terminals of the thermal relay are normal. Use the multimeter resistance gear to measure the interphase resistance of the thermal relay in two, and it still shows infinity! After looking around the scene, I thought for a second and then copied the 500V megohmmeter around me and carried out the phase-to-phase insulation measurement of the thermal relay. After only two turns of the megohmmeter, a surprising scene happened - the insulation resistance measured by the multimeter was safe, but it went to zero under the pressure of DC500V, and there was a intermittent and subtle "hissing" discharge sound inside the thermal relay!

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