Troubleshooting and Maintenance of Inverter IGBT Module
A certain pumping unit frequency converter equipment is a 1140v/30kw pumping unit dedicated frequency converter. During operation, the IGBT module in the middle phase was burnt black, and one leg of the bus peak absorption capacitor (3 μ f/1200v non inductive capacitors connected in series and parallel) was broken, making it unable to operate normally.
Fault phenomenon
A certain pumping unit frequency converter equipment is a 1140v/30kw pumping unit dedicated frequency converter. During operation, the IGBT module in the middle phase was burnt black, and one leg of the bus peak absorption capacitor (3 μ f/1200v non inductive capacitors connected in series and parallel) was broken, making it unable to operate normally.
Preliminary judgment
Using a multimeter to test the main circuit section, the middle phase was blackened, but the test was successful and the other two phases were also normal.
Repair process
(1) Firstly, replace the damaged components. After replacing the 3 μ f/1200v capacitor, close the isolation switch and power the control cabinet. The control cabinet did not respond, the power light did not light up, and the voltmeter did not indicate.
(2) There is a high-voltage fuse connected to the input terminal, and it is suspected that it is damaged. Use a multimeter to check the voltage of the three terminals behind the fuse in the high voltage range, and all are normal at 690V. As the control circuit uses a 220V power supply, it is suspected that there is a problem with the 1140/220V transformer. Later, after the power was cut off, a multimeter was used to check the resistance values at both ends of the fuse. One of them was connected, while the other two were disconnected. It was determined that the original judgment was incorrect and that two fuses were blown. Detecting the fuse, there is a power display indicating that the primary winding of the 1140/220V transformer has not been disconnected. As it is a single-phase power supply, voltage cannot be formed, and the 1140/220V transformer does not work. The control cabinet cannot work due to the lack of voltage.
(3) After replacing the fuse, the cabinet was powered on normally, the power frequency started, and the operation was normal. The power frequency maintenance was completed. Next, repair the frequency conversion part.
(4) Connect the control power. As soon as the power is turned on, the fault protection light on the display panel lights up, suspecting interference. However, this has been the case multiple times during power outages, as it is in a protected state and cannot be turned on. After unplugging the short-circuit protection plug (due to the main circuit not being powered on, the control circuit was powered on without any impact), the power supply was normal. The startup is also normal. Use a multimeter to check the voltage when the frequency reaches 50Hz. The three-phase output voltage is balanced, with a line to line voltage of 8.2V and a neutral line voltage of 5.0V, indicating normal operation.
(5) Check the short-circuit protection board. Unplug the input short-circuit protection sampling current sensor and measure the power supply voltage on the board. ± 12v is normal, but the+5V power supply voltage is+3.0v. Unplug the integrated fast 74hc14 and the+5V is normal, indicating that the integrated block is damaged. Replace it with a new one.
(6) Plug in the input short-circuit protection sampling current sensor. First plug in the current sensor on the positive busbar, measure ± 12v, and it works normally; Insert the current sensor on the negative bus again and measure the ± 12v voltage.+12V+9.0V, -12V is normal. The current sensor on the negative bus is damaged. Remove and replace the current sensor.
(7) Plug in all unplugged cables and connect them to the motherboard. Connect the control power and work normally. To further verify the working condition, a voltage of 220V was applied to the main circuit, and it worked normally after startup. The line to line voltage was 220V, and the neutral line voltage was 130V (at 50Hz), indicating normal operation.
(8) Stop the power frequency and turn on the frequency converter. But as soon as the frequency converter is turned on, a short circuit protection occurs. After disconnecting the load, the frequency converter ran without load and also experienced short circuit protection. This analysis shows that the control power supply is normal, and the addition of 220V is also normal. It is suspected that the device has insufficient voltage resistance. After the power outage, the original burnt black module will be replaced. Replace the transmission control and send 220v, all working normally. The main power supply is 1140V, turned on to 50Hz, and works normally.
(9) Connect the load and run with it. But there was a problem again, and a short circuit protection appeared when the machine was turned on. The motor was also detected to be normal, but later it was considered whether the current sensor on the negative bus was also damaged. During the control power detection, when in static state, there is a voltage of+3.0V at both ends of the sampling resistor of the current sensor signal. Since there is no current in static state, it should be 0V under normal circumstances, indicating that the sensor is damaged. After replacing it with a new one, the detection is normal after startup.
(10) Finally, send control and main power, working normally with load, working normally
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