Method of using a multimeter to detect frequency converters
Static testing
1. Test the rectifier circuit to find the P and N terminals of the internal DC power supply of the frequency converter. Set the multimeter to resistance X10, connect the red meter rod to P, and connect the black meter rod to R, S, and T. There should be a resistance value of about tens of ohms, and it should be basically balanced. On the contrary, connect the black meter rod to the P end, and the red meter rod to R, S, and T in sequence, with a resistance value close to infinity. Connect the red meter rod to the N-end and repeat the above steps to obtain the same result. If there are the following results, it can be determined that the circuit has malfunctioned,
A. The three-phase imbalance of resistance can indicate a fault in the rectifier bridge.
B. When the red meter rod is connected to the P terminal, the resistance is infinite, which can determine whether the rectifier bridge is faulty or the starting resistor is faulty.
2. Test the inverter circuit by connecting the red meter rod to the P terminal, and the black meter rod to U, V, and W respectively. There should be a resistance value of tens of ohms, and the resistance values of each phase should be basically the same. The reverse phase should be infinite. Connect the black meter rod to the N-end and repeat the above steps to obtain the same result. Otherwise, it can be determined that the inverter module is faulty. Secondly, dynamic testing can only be carried out after the static test results are normal, that is, power on testing. Before and after powering on, the following points must be noted:
1. Before powering on, it is necessary to confirm whether there is an error in the input voltage. Connecting a 380V power supply to a 220V level frequency converter may cause the machine to explode (such as capacitors, varistors, modules, etc.).
2. Check if the various broadcast ports of the frequency converter are properly connected and if there is any looseness in the connection. Abnormal connection may sometimes cause the frequency converter to malfunction, and in severe cases, it may cause the machine to explode.
3. After powering on, check the fault display content and preliminarily determine the fault and its cause.
4. If no fault is displayed, first check if there are any abnormalities in the parameters, reset the parameters, start the frequency converter under no-load (without connecting the motor), and test the three-phase output voltage values of U, V, and W. If there is a lack of phase, three-phase imbalance, etc., the module or driver board may have a fault
5. Under normal output voltage (no phase loss, three-phase balance), conduct load testing. When testing, it is best to conduct a full load test.
