In daily work, we may encounter a situation where the frequency converter shows no response after power-up. Normally, if a fault occurs, the frequency converter will display a corresponding fault code. So what causes a complete lack of response? And how should we carry out troubleshooting?

Troubleshooting Procedures

1. Check the power switch

First verify whether the power switch is energized. A faulty power switch will prevent the frequency converter from starting normally; replace the switch if needed.

2. Static test

Measure the resistance of the frequency converter with a multimeter. Set the multimeter to the ×10 resistance range. Connect the red probe to terminal P of the frequency converter, then touch the black probe to R, S and T terminals one by one. The measured resistance should be roughly several tens of ohms and balanced across the three phases. Next, swap the probes: connect the black probe to terminal P, then touch the red probe to R, S and T in sequence. The reading will be nearly infinite resistance. Then connect the red probe to terminal N and repeat the above steps. If the readings remain consistent, the static test result is normal.

3. Dynamic test

Start the frequency converter under no-load condition and observe the three-phase output voltage of U, V, W. Check for phase loss or three-phase voltage imbalance, which may indicate faults in the power module or drive board. If the output voltage is normal, proceed to a load test.

Solutions

1. Power supply fault: Check whether the power supply works properly and ensure power connection.

2. Incorrect parameter settings: Review the frequency converter parameters to confirm they match the motor.

3. Faulty external control signal: Verify the external control signals from PLC or other control devices.

4. Faulty power module or drive board: Phase loss or three-phase imbalance found in dynamic testing points to faults of the power module or drive board.