1. How to Distinguish Between Heavy Faults and Light Faults?
When a light fault occurs, the system will issue an alarm signal, and the fault indicator will flash. In contrast, when a heavy fault is detected, the system will provide a continuous fault indication, and the fault indicator will remain on. Additionally, the system will automatically trigger a high-voltage disconnection command and close the switch. The fault information and the high-voltage disconnection command are stored in memory. The fault status remains active until it is resolved, and both the fault indication and the high-voltage disconnection command continue to be valid.
2. What Are Light Faults?
Light faults include: transformer over-temperature alarm, cabinet temperature over-temperature alarm, cabinet door open, unit bypass. These faults do not get stored by the system, only the fault indication is displayed. Once the fault is cleared, the alarm is automatically reset. A light fault alarm during inverter operation does not stop the system, and even if it occurs during shutdown, the inverter can still run normally.
3. What Are Specific Faults?
When the following faults occur in the system, the system handles them accordingly, and the fault type is displayed in the upper left corner of the monitor: external fault, transformer overheat, cabinet overheat, unit fault, inverter overcurrent, high voltage loss, interface board fault, controller no communication, interface board not communicating, motor overload, parameter error, main control board failure. Unit failures include: fuse failure, unit overheating, drive failure, fiber failure, and unit overvoltage. External faults must be removed from the high-voltage disconnect state (via the door button or external contact) before system reset to restore normal operation. After a major fault other than an external fault, a direct system reset can restore the system. However, it is essential to identify the cause of the fault before powering up again. After a unit failure, the unit status can only be detected by applying high voltage power again. If the fault is difficult to analyze and you're unsure whether it's safe to reapply high voltage, consult the manufacturer. Note: Never rush to power up without identifying the fault cause, as this could seriously damage the inverter!
4. Transformer Over-Temperature Alarm
When the transformer temperature controller measures a temperature above its set alarm temperature (default is 100°C), the temperature controller’s over-temperature alarm contact closes. Check if the fan at the top of the transformer cabinet or the fan at the bottom of the cabinet is working properly. If the bottom fan isn’t functioning, there may be a large difference in three-phase temperatures. Also check if the temperature measuring resistor is normal (no wire breakage, good plug contact). Poor contact can result in high temperature readings. Check if the filter is clogged (use an A4 paper to test for suction; clean if necessary). Ensure the inverter is not operating under long-term overload. Check if the ambient temperature is too high (should be below 45°C; otherwise, improve ventilation with wall-mounted fans or air ducts). Verify that the fan switch and contactor at the bottom of the transformer cabinet are not disconnected. Confirm that the control and protection circuit of the transformer cabinet fan is normal.
5. Cabinet Temperature Over-Temperature Alarm
If the temperature at the unit cabinet temperature measurement point exceeds 55°C, the system will trigger a cabinet temperature over-temperature light fault. Check if the top fan of the unit cabinet is operating correctly, whether the fan switch in the secondary room is tripped, if the filter is blocked (test with an A4 paper for suction; clean if needed), if the system is running under long-term overload, if the ambient temperature is too high (should be below 45°C; otherwise, reinforce with fans or refrigeration equipment), and if the transformer cabinet fan control and protection circuit is normal.
6. Transformer Overheating
If the transformer temperature controller measures a temperature above its set trip temperature (default is 130°C), the temperature controller’s trip contact closes, and the system reports a transformer overheat fault. Check if the temperature displayed by the controller is above 130°C. If not, verify that the over-temperature alarm value is set to 130°C. For other checks, refer to the transformer over-temperature alarm section.
7. Cabinet Temperature Overheating
If the temperature at the unit cabinet temperature measurement point exceeds 60°C, the system will report a heavy fault due to cabinet temperature overheating. Refer to the cabinet temperature over-temperature alarm section for checking procedures.
8. Cabinet Door Interlocking Alarm Travel Switch
Check if the travel switch is properly compressed against the top of the cabinet door. Ensure the “pre-stroke†and “over-stroke†settings are appropriate. Verify that the electrical function of the travel switch is working properly. If not, replace the interface board.
9. Controller Does Not Communicate
Confirm that the communication line from the monitor control board to the main control board is connected correctly. Check that the +15V and +5V voltages on the monitor control board are correct. Replace the main control board or the monitor if needed.
10. Main Control Board Fault
If the monitor detects a faulty main control board after establishing communication with the controller, it will report a main control board fault. Replace the monitor or the main control board.
11. Interface Board Does Not Communicate
The interface board resets the monitor every 5 seconds. If communication is not established within 3 minutes and 30 seconds, it is considered a heavy fault. Check if the communication line is normal, if the terminal connections are correct, if the I/O board is working properly, especially its working voltage, and if the external chip on the I/O main control board is properly inserted.
12. Parameter Error
A parameter error occurs when an incorrect parameter is set, possibly during synchronous vector control. Re-enter the correct parameters and press the reset button.
13. External Fault
If the local high-voltage disconnect button is pressed or the high-voltage disconnect contact on the interface board is closed, the system will report an external fault. Check if the high-voltage breaking button is pressed, if the high-voltage breaking terminal is shorted, or if the interface board is damaged.
14. High Voltage Power Supply Disappears
This usually happens during normal opening operations. If there is an abnormal high-voltage power failure (no fault record, no trip operation), check the upper switchgear opening circuit.
15. Inverter Overcurrent
If the inverter output current exceeds 1.5 times the rated current, the inverter will trigger overcurrent protection. Check the output voltage detection board, look for signs of short circuits or discharge traces, ensure the optical fiber is securely inserted, and verify that the main circuit connection screws are tight. Check the Hall element power supply and output current signal. Confirm that the acceleration time setting is not too short, torque boost is not too high, and starting frequency is not too high. Check if the motor or load machinery is jammed, or if the motor windings or output cable insulation is damaged. Ensure all units are working properly (remove the unit, connect copper bars, and use a multimeter or oscilloscope to check input and output voltages and waveforms). Check if the input power supply voltage is too low. Check if there is a power factor correction capacitor or surge absorbing device on the inverter output side that might cause resonance with the inductor. Remove such devices if necessary. Check if the unit detection board is short-circuited or damaged. If the above causes are still present, replace the controller signal board or main control board. In some cases, cogging effects may cause large current fluctuations at low motor speeds, leading to current limiting and overcurrent protection. In such cases, reduce the acceleration time and increase the current limiting coefficient to help the motor pass through the fluctuation region. If the unit output voltage is low, replace the unit.
16. Motor Overcurrent
If the motor output current exceeds 1.2 times the rated current and lasts more than 2 minutes, the system will report an overcurrent fault. Check if the motor rated current setting is correct, if the motor or load machinery is jammed, or if the power supply voltage is too low.
17. Motor Does Not Rotate After Inverter Starts
Check if there is any contactor or switch-type equipment on the inverter output. Confirm that the inverter output primary cable is connected to the motor. Observe if the monitor shows output current and voltage. If there is voltage but no current, the inverter’s main circuit to the motor is open. If there is voltage and current, check if the cable has single-phase grounding or if the motor rotor winding is open.
18. Unit Heavy Faults (Fuses, Drives, Overheating, Overvoltage, Fiber Faults)
There are five types of unit faults: fuse faults, drive faults, unit overheating, unit overvoltage, and fiber faults. The first three can be bypassed if the unit has a bypass function and the number of bypass stages is set to non-zero.
19. Fuse Failure
If the unit detects a phase loss, it indicates a fuse failure. Check if the main power is off, if the three-phase incoming lines are loose, or if the incoming fuse is intact. If the fuse is open, replace the unit.
20. Drive Fault
Check if the unit voltage detection board is short-circuited. A short circuit can cause A1, B1, and C1 units to report drive faults. Check if the power unit output terminals L1 and L2 are short-circuited. If so, the unit IGBT may be damaged, and the unit should be replaced. Check if the motor insulation is intact and if there is any mechanical failure in the load.
21. Unit Overheating
A temperature switch (normally closed) is installed on the radiator inside the unit. When the temperature exceeds 85°C, the temperature relay closes, and the unit is reported as overheated. Check if the fan at the top of the cabinet is working, if the unit cabinet fan switch is tripped, and if the filter is blocked (test with an A4 paper for suction; clean if needed). Check if the ambient temperature is too high (should be below 45°C; otherwise, improve ventilation with fans or air ducts). Finally, check if the power unit temperature relay is functioning properly.
22. Unit Overvoltage
If the DC bus voltage exceeds the protection value, the inverter will report overvoltage. During operation, if a unit’s output voltage is low, it can cause unbalanced three-phase output, leading to overvoltage in the unit. During no-load motor commissioning, overvoltage is more likely to occur in A1/B1/C1 units. At this time, the reference voltage can be appropriately reduced. Check if the input high-voltage power supply exceeds the maximum allowable value (if too high, adjust the transformer tap to 105%). If overvoltage occurs during deceleration, increase the inverter’s deceleration time setting.
23. Fiber Fault
If the system does not detect unit communication in the power-on state, it indicates a fiber fault. Check if the power unit control power supply is normal (green indicator light on). Otherwise, replace the power unit. Check if the power unit and controller fiber connector are disconnected or if the fiber is broken.
24. Unit Bypass
If the unit is configured with bypass hardware and the number of bypass stages in the parameter setting is non-zero, and the unit has three faults—drive fault, fuse fault, and unit overheat—the unit bypass will occur. If a unit fails to bypass, the other two units in the same position will also be bypassed. At this time, the inverter can still start and operate, but the rated output voltage and capacity will be reduced due to fewer series units per phase. When a unit bypass occurs, find out the cause and isolate the faulty unit as soon as possible (the remaining two phases are bypassed without replacement). Clean the unit drive board and control board. If the boards are too dusty, it may cause false positives.
25. Operating Frequency Is Inconsistent With Given Frequency
This situation can occur due to several reasons. During acceleration and deceleration, the output frequency may reach the given frequency due to the limitation of acceleration and deceleration time. If the system voltage is too high, the inverter will decelerate to avoid DC bus overvoltage. This is a protective measure, so the frequency cannot stay at a fixed point. It is recommended to adjust the transformer tap to 105%. If the inverter output current exceeds the set current limit, the inverter will automatically reduce the frequency to avoid overcurrent trips. This often happens when the input voltage is too low or the load suddenly increases. During a momentary power failure, the inverter will decelerate to maintain motor controllability. A faulty Hall element, unit detection board, or signal board can also cause this issue.
26. Monitor Black Screen
Press the system reset button on the door (this will not affect the inverter’s normal operation). If it still doesn’t recover, check if the monitor’s power terminal is off, if the cable is loose, if the 5V and 15V power supplies are normal, and if the monitor circuit is damaged. If interference is suspected, replace the monitor.
27. Parameters Cannot Be Modified
If the parameter modification option is disabled in the function parameter, most parameters cannot be modified, except for the parameter and the given frequency or given parameter. Most parameters cannot be changed while the system is running.
28. Inverter Automatically Restarts After Stopping
In remote control mode, the start and stop must be controlled via the remote terminal. If the start mode in the parameter setting is level start (closed start, disconnected stop), and the emergency stop signal is released during operation or the inverter is stopped by other means, the inverter will stop freely. However, once the emergency stop signal is reconnected, the inverter will automatically restart because the remote start level signal is still active.
29. Inverter Trips Upon Power-On
When the inverter is powered on, the instantaneous RMS current can reach 6–7 times the inverter’s rated current for tens of milliseconds. If the protection setting is too small, it may trigger the upper switchgear’s quick-break protection. Adjust the quick-break protection setting of the upper switchgear.
30. Output Frequency Fluctuates at Low Speed During Startup
Some motors experience large current fluctuations at low speeds due to cogging effects. At this point, the inverter may activate current limiting, causing repeated acceleration, current limiting, and deceleration, preventing normal acceleration. Increase the current limit setting, shorten the startup time, or replace the unit if its output voltage is low.
31. Automatic Bypass Cabinet Bypasses When Upper Switchgear Trips
Check if the delay pull-in time relay in the bypass cabinet is between 1.5S and 3S. Ensure the switch cabinet setting is not too small (should be more than 5 times the motor’s rated current). Set the quick-break protection time of the switch cabinet to be greater than 0.1S.
32. External Terminal Has Induced AC Voltage
It may be induced voltage from remote start/stop, high-voltage disconnection, or system reset signal lines. It is recommended to separate passive signals from the 220V AC power supply. Ground both ends of the shielded wire. It may also be induced voltage from the signal line on the remote control box and the power line. It is better to rewire the remote control box and use shielded cables for the signal lines. Avoid making the shielded wire too long. For 4–20mA current signals with AC induced voltage (below 10V), connect a 275V/0.33uf capacitor between the current signal and ground.
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