1. Locate the P(+) and N(-) terminals of the DC power supply inside the inverter. Set the multimeter to diode mode, connect the black probe to the P(+) terminal of the inverter, and measure the R, S, and T phases in sequence with the red probe. If the readings are the same and basically balanced, the inverter is working properly. If the measured values are different, the inverter module is damaged.
2. Locate the P(+) and N(-) terminals of the DC power supply inside the inverter. Set the multimeter to diode mode and connect the red probe to the N(-) terminal of the inverter. Measure the U, V, and W phases in sequence with the black probe. If the readings are the same and basically balanced, the inverter is working properly. If the measured values are different, the inverter module is damaged.
annotation:
1. When testing the inverter module, remove the automatic resistors at terminals R, S, T and U, V, W of the inverter.
2. The same method can be used to measure the quality of various frequency converters.
3. If the inverter reports overvoltage or undervoltage, check if the inverter module is damaged. Use the above method to measure the inverter's condition.
4. Sometimes, if the main switch trips, it may be due to a faulty inverter module. Do not rush to power it on. Use the methods above to test the inverter to determine if it is good or bad.
Measurement of DC bus voltage
1. Measurement purpose: When the frequency converter reports a phase loss or undervoltage, but the input voltage is normal, this voltage is measured to determine which part of the internal circuit of the frequency converter is malfunctioning.
2. Measuring instruments: DC voltmeter, select 1000V DC range.
3. Measurement Method: Connect the red probe to point P on the DC bus (with corresponding terminals), and the black probe to point N. Read the measured voltage value. According to the rectification principle, the inverter should be measured under load. Only by measuring under load can a voltage drop be detected. If the voltage is below 470V under load, the filter capacitor's capacitance has decreased; if it is below 400V, a phase loss has occurred.
