Experience and skills of inverter maintenance
At present and for a period of time in the future, the maintenance work for electrical control equipment such as frequency converters will become the professional knowledge that some electrician practitioners need to master. JACT will introduce the following maintenance methods that are simple and easy to master, and share them with the majority of inverter maintenance workers. I hope that these methods can help you in inverter repair work.
1. First disconnect the incoming lines R, S, T and outgoing lines U, V, W of the inverter, and then measure whether the rectifier circuit and the inverter circuit are normal. 1. To test the rectifier circuit, set the multimeter to resistance X10, connect the red test lead to the P terminal, and the black test lead to the R, S, and T terminals in turn. There should be a resistance value of about tens of ohms, and basically balanced. Connect the black test lead to the P terminal, and the red test lead to R, S, and T in turn. There is a resistance close to infinity. Connect the red test lead to the N terminal and repeat the above steps, the same result should be obtained. If the three-phase resistance is unbalanced or the resistance is infinite when the red test lead is connected to the P terminal, it can be judged that the circuit is abnormal and the rectifier bridge is faulty.
2. After the inverter fails and the power is turned off, quickly disassemble the machine and do a good job of protection. Use the belly of your finger to quickly touch the relevant electronic components and IC integrated blocks on the internal circuit board of the inverter. Once it is found that some components have a significant year-on-year temperature rise, the fault must be on it or in the surrounding circuits! For example, a certain brand of 35KW inverter caused DC bus overvoltage protection due to the deterioration of the resistance of the DC bus voltage monitoring resistor. From the figure, you can feel how high the heat emitted by the resistor was during the incident!
3. When the frequency converter is working, if there is a phenomenon of good and bad working time, it may be caused by open welding failure of some components in the internal circuit. For some chip ICs with finely arranged pins and numerous SMD ICs, it is not easy to find out if there are any problems simply by visual observation. At this moment, we might as well use insulated plastic rods/wood rods (conducting metal objects are strictly prohibited), and press the suspected components with appropriate force when the power is on. This method is very effective for eliminating small SMD components, especially SMD ICs, but it must be done to prevent electric shock and short-circuit during operation.
4. Relying on the feeling of percussion. This method is a supplement to the previous detection method. It can only be effective for small SMD components, but not for some high-power electronic components or circuit parts with high voltage danger. Easy to operate. For this, we can change the pressure to knocking, and use an insulating tool to knock with appropriate force near the suspected fault point. In most cases, the fault object can be quickly locked. The false solder joints of the components that caused a small-capacity inverter to intermittently report overvoltage faults detected by this method!
5. You can also touch with a meter pen to measure whether the inverter is faulty. The black test pen touches the negative pole P(+) of the DC bus, the red test pen touches R, S, T in turn, and records the displayed value on the multimeter. The red test pen touches N(-), and the black test pen touches R, S, T in turn, and record the multimeter. If the displayed value of the six times is basically balanced, it indicates that there is no problem with the inverter diode rectification or soft-start resistance. On the contrary, the rectifier module or soft-start resistance in the corresponding position is damaged.
The red test pen touches the negative pole P(+) of the DC bus, the black test pen touches U, V, W in turn, and records the displayed value on the multimeter. The black test pen touches N(-), and the red test pen touches U, V, W in turn, and record the multimeter. If the displayed value of the six times is basically balanced, it indicates that there is no problem with the inverter IGBT inverter module. On the contrary, the IGBT inverter module in the corresponding position is damaged.
The next article will continue to introduce practical experience and operating skills for inverter maintenance. If you are interested, you can pay more attention to JACT.
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