Here are the common methods for repairing and testing frequency converters that Shanghai Hongsu's senior maintenance engineer will explain to you:
The first method is to test the rectifier circuit: find the P and N terminals of the DC power supply inside the frequency converter, adjust the multimeter to resistance X10, connect the red meter rod to P, and connect the black meter rod to R, S, and T respectively. Normally, there is a resistance value of several tens of ohms, and it is basically balanced. On the contrary, connect the black meter rod to the P end, and then connect the red meter rod to R, S, and T in sequence, with a resistance value close to infinity. Connect the red rod to the N end and repeat the above steps to obtain the same result. If the resistance values of the three phases are unbalanced, it indicates a fault in the rectifier bridge; When the red meter rod is connected to the P terminal and the resistance is infinite, it can be concluded that there is a fault in the rectifier bridge or a fault in the starting resistor.
The second method is to test the inverter circuit: connect the red meter rod to the P terminal, and connect the black meter rod to U, V, and W respectively. There should be a resistance value of several tens of ohms, and the resistance values of each phase should be basically the same. The reverse phase should be infinite. Repeat the above steps with the N end of the black meter rod to obtain the same result, otherwise it can be determined that there is a fault in the inverter module.
The above two methods are static testing, and sometimes dynamic testing can also be used. Shanghai Hongsu's senior inverter maintenance engineer reminds you to pay attention to the following points when conducting dynamic testing: before powering on, you must confirm whether the input voltage is correct. Connecting the 380V power supply to the 220V level inverter may cause the machine to explode; Check if the interfaces of the frequency converter are properly connected and if there are any loose connections. Abnormal connections may sometimes cause the frequency converter to malfunction, and in severe cases, it may even explode; After powering on, detect the fault display content and preliminarily determine the fault and its cause; If no fault is displayed, first check whether the parameters are abnormal, reset the parameters, start the frequency converter under no-load (without connecting the motor), and test the output voltage values of U, V, and W phases. If there is a phase loss, three-phase imbalance, etc., the module or driver board is faulty; When the output voltage is normal (no phase loss, three-phase balance), load testing should be conducted at full load as much as possible.
Frequency converter maintenance is a work that combines theoretical knowledge, practical experience, and operational level, and its technical level determines the quality of frequency converter maintenance. Personnel engaged in frequency converter maintenance need to regularly learn, understand the functions and characteristics of the electronic components inside the frequency converter, broaden their knowledge, apply newly learned knowledge to practical work, and continuously improve their maintenance skills. Shanghai Hongsu Automation Technology Co., Ltd. is one of the earliest companies in China specializing in the maintenance of various industrial, military, aerospace and other fields of equipment frequency converters. We sincerely welcome domestic enterprises and industrial automation, transmission control, and equipment manufacturers from various countries to visit and establish business relationships with us.