How to do a good job in the maintenance of power frequency converters
1. Based on the actual environment, determine the length of the cycle interval for comprehensive inspection and maintenance of the frequency converter. If necessary, disassemble, inspect, measure, remove dust, and tighten the rectifier module, inverter module, and circuit board inside the control cabinet. Due to the frequent blockage of the lower air inlet and upper air outlet of the frequency converter due to dust accumulation or excessive dust accumulation, the heat dissipation capacity is high and ventilation is required. Therefore, after running for a certain period of time, There is dust accumulation on the circuit board (due to static electricity), which needs to be cleaned and inspected.
2. After repairing the circuit board, busbar, etc., necessary anti-corrosion treatment should be carried out, insulation paint should be applied, and the busbar that has undergone partial discharge or arcing should be deburred and insulated. For insulation columns that have been insulated and broken down, carbonization must be removed or replaced.
3. Check and tighten all wiring terminals to prevent serious heating caused by looseness.
4. Conduct a comprehensive inspection and parameter measurement of input (including output) terminals, rectifier modules, inverter modules, DC capacitors, and fast melting devices. If any devices are found to be burnt or have significant parameter changes, they should be replaced in a timely manner.
5. Regularly and carefully check the rotation status of the fan inside the frequency converter. After the power is cut off, rotate the fan blades by hand, observe whether the bearings are stuck or not rotating flexibly, and replace them if necessary.
6. Carefully inspect the electronic components on the control circuit board, check and handle abnormal phenomena such as solder detachment, discoloration, bulging, cracking, and wire breakage (printed board circuit). If necessary, components with external abnormalities can be measured and replaced from the circuit board.
In practice, the decrease in capacitor capacity is directly related to the operating environment, load size, working system, and other conditions of the frequency converter. Severe environments, larger loads, frequent shutdowns, and other operating conditions can accelerate the aging of the DC main capacitor. In addition, during regular maintenance, it is necessary to carefully inspect the main DC circuit capacitor for any leakage, expansion, blistering or deformation of the shell, and whether the safety valve is opened. The capacitor capacity, leakage current (high leakage current can cause overheating of the capacitor, causing the safety valve to open, or even the capacitor to explode), and voltage resistance should be tested. Capacitors with a capacity reduction of more than 30%, leakage current exceeding 70mA, and voltage resistance below 650V should be replaced in a timely manner. For new capacitors or capacitors that have not been used for a long time, performance testing should be conducted to meet the usage requirements before they can be replaced.
8. For devices with high current carrying capacity such as rectifier blocks and inverter GTRs (or IGBTs), instruments and tools such as multimeter and bridge should be used for testing and voltage withstand tests. The forward and reverse resistance values should be measured and recorded in a table. Modules with significant parameter differences should be replaced.
9. Check the main contactor and other auxiliary relays, carefully observe whether the dynamic and static contacts of each contactor have arcing, burrs, or surface oxidation, unevenness, etc. If such problems are found, the corresponding dynamic and static contacts should be replaced to ensure safe and reliable contact.
10. Regularly check the voltage fluctuation of the frequency converter power supply. We need to improve the phenomenon of frequency converters in special usage environments and large load fluctuations to avoid the impact of high currents on the frequency converter, which may affect its normal operation.
Frequency converters are widely used in industries such as metallurgy, petrochemical, power, machinery, and civil appliances due to their wide speed range, fast dynamic response, high speed regulation accuracy, complete protection functions, and simple operation. In general, after using the frequency converter for about 7 years, it will enter a period of frequent faults, which may lead to component burnout, failure, frequent action of protection functions, and other faults, seriously affecting its normal operation.
