I. Inverter repair and power-off test results
(1) Inverter repair and testing of rectifier circuit
When testing the two ends of the internal DC power supply of the frequency converter, P and N, set the multimeter to the resistance RX10 range. Connect the red probe to the P end and the black probe to R, S, and T in sequence. Normally, there should be a resistance of several tens of ohms, and the resistance should be basically balanced. Conversely, if you connect the black probe to the P end and the red probe to R, S, and T in sequence, there should be a resistance close to infinity. If you connect the red probe to the N end and repeat the above steps, the result should be the same.
If any of the following three results occur, it can be determined that the inverter's repair circuit has malfunctioned: ① Uneven resistance across the three phases indicates a fault in the rectifier bridge. ② Infinite resistance when the red probe is connected to the P terminal or the black probe to the N terminal indicates a fault in the rectifier bridge or a fault in the dynamic resistor. ③ Near-zero resistance when the red probe is connected to the P terminal or the black probe to the N terminal indicates a short circuit in the rectifier bridge.
(2) Inverter circuit repair and testing
Connect the red probe to terminal P, and the black probe to terminals U, V, and W respectively. There should be a resistance of several tens of ohms, and the resistance of each phase should be similar. The resistance of the reverse phase should be infinite. Connect the black probe to terminal N and repeat the above steps. You should get the same result. Otherwise, it can be determined that the circuit breaker module is faulty.
II. Power-on test results for frequency converter repair
After confirming that the rectifier and inverter circuits are functioning correctly without power, a power-on test is then performed on the inverter. The following points must be noted before and after powering on:
① Before powering on, you must confirm that the input voltage is correct. If a 380V power supply is mistakenly connected to a 220V input voltage inverter, it will cause the inverter to explode (capacitors, varistors, modules, etc. will explode).
② Check whether all the interfaces of the frequency converter are connected correctly and whether the connections are loose. Abnormal connections may sometimes cause the frequency converter to malfunction, and in severe cases, it may cause the frequency converter to explode.
③ After powering on, check the fault display content and make a preliminary determination of the fault and its cause.
④ If no fault is displayed, first check if the parameters are abnormal, and after resetting the parameters, start the frequency converter under no-load (without connecting the motor) conditions, and test the three-phase output voltage values of U, V, and W. If there is a phase loss, three-phase imbalance, etc., then the module or drive board is faulty.
⑤ When the output voltage is normal (no phase loss, three-phase balance), negative tests should be performed at full load as much as possible.
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