Inverter Troubleshooting: 32 Inverter Failure Causes and Solutions


What are the common faults of inverters?

How to distinguish between heavy and light faults?

Let’s take a look at the inverter failure causes and 32 treatment methods.

Inverter Troubleshooting

1. How to distinguish between heavy failure and light failure?

In case of minor faults, the system issues an alarm signal and the fault indicator flashes.

When a serious fault occurs, the system issues a fault indication, and the fault indicator is always on.

At the same time, a command is issued to break the high voltage and the closing is prohibited, and the fault information and the high voltage breaking command are processed for memory.

The heavy fault state is not eliminated, and the fault indication and high-voltage breaking command are still valid.

2. What are the minor faults?

The minor faults include: transformer over-temperature alarm, cabinet temperature over-temperature alarm, cabinet door opening, unit bypass, the system does not memorize minor faults, only fault indication, and the alarm will be automatically eliminated after the fault disappears.

If a minor fault alarm occurs during the operation of the inverter, the system will not stop.

The minor fault alarm occurs during shutdown, and the inverter can continue to start running.

3. What are the heavy faults?

When the following faults occur in the system, they are handled according to major faults, and the major fault type is displayed on the upper left corner of the monitor.

For example, external faults, transformer overheating, cabinet temperature overheating, unit faults, inverter over-current, high voltage power loss, interface board failure, the controller does not communicate, interface board does not communicate, motor overload, parameter error, main control board failure.

Unit failures include fuse failure, unit overheating, drive failure, fiber failure, and unit over-voltage.

For external faults, the state of high-voltage breaking (cabinet door button or external contact) must be released before the system is reset, so that the system can return to the normal state.

After the occurrence of heavy faults other than external faults, a direct system reset can restore the system to a normal state, but the cause of the fault must be found before powering on again.

After a unit failure has occurred, the unit state can only be detected if the high voltage power is turned on again.

If the fault is difficult to analyze and it is not possible to determine whether secondary high pressure can be applied, please consult the manufacturer.

Note: Never turn on the power twice without identifying the cause of the failure, otherwise the inverter may be seriously damaged!

4. Transformer over-temperature alarm, when the transformer thermostat measurement temperature is greater than its set alarm temperature (default setting is 100 ℃), the thermostat over-temperature alarm, contact closure.

  • Check that the transformer’s overhead or under-cabinet fan is working properly (if the under-cabinet fan is not working properly, there may be a large difference in temperature between the three phases).
  • The temperature resistance is measured properly (no broken wires, poor contact with the line plugs, if poor contact, the temperature value will be high).
  • Whether the filter is clogged (take an A4 sheet of paper and place it on the filter to see if it can be absorbed, otherwise the filter needs to be cleaned).
  • Whether the frequency inverter is operating under long-term overload.
  • Whether the ambient temperature is too high (ambient temperature should be below 45°C, otherwise better ventilation is required).
  • Whether the fan switch and contactor mounted on the bottom front of the transformer cabinet are disconnected.
  • Is the transformer cabinet fan control and protection circuitry in order.

5. When the temperature of the temperature measurement point of the over-temperature alarm unit cabinet is greater than 55 ℃, the system will send the failure alarm.

  • Check whether the fan on the top of the unit cabinet is working properly and whether the fan switch installed in the secondary room has tripped;
  • Whether the filter is clogged (take an A4 sheet of paper and place it on the filter to see if it can be absorbed, otherwise the filter needs to be cleaned).
  • Whether the inverter is permanently operated in an overload state.
  • Whether the ambient temperature is too high (ambient temperature should be below 45°C, otherwise ventilation needs to be enhanced (wall ventilators or ducts on top of cabinets) or refrigeration equipment installed).
  • Is the transformer cabinet fan control and protection circuitry in order.

6. When transformer overheating, transformer temperature measurement temperature is greater than its set trip temperature (default setting is 130 ℃), the temperature controller trip contact closed, the system will report the transformer overheating heavy failure.

Whether the temperature displayed by the thermostat is above 130 degrees, if not, check whether the thermostat’s over-temperature alarm value is set to 130 degrees.

See transformer over-temperature alarm for the remaining checks.

7. The cabinet temperature is too hot.

When the temperature of the unit cabinet temperature measurement point is greater than 60 ℃, the system will report the cabinet temperature overheating heavy failure.

See cabinet temperature over-temperature alarm for inspection items.

8. The cabinet door interlocking alarm travel switch is compacted with the top of the cabinet door.

Whether the “pre-travel” and “over-travel” of the travel switch are suitable; whether the electrical function of the travel switch is working properly, otherwise replace the interface board.

9. The controller does not communicate.

Make sure the communication cable from the monitor control board to the main control board is connected correctly, and make sure the +15V and +5V on the monitor control board are correct.

Replace the main control panel. Replace the monitor.

10. Main control board failure.

The monitor has established communication with the controller, the monitor detects a fault in the main control board, then reports a fault in the main control board.

Replace the monitor.

Replace the main control panel.

11. The interface board is not working.

The monitor does not establish communication with the interface board, which will reset every 5 seconds.

If the monitor, at 3 minutes and 30 seconds, does not establish communication, it will be judged as a heavy failure.

  • Check that the communication lines are normal and the terminals are correct.
  • Whether the I/O board is working properly, especially the operating voltage.
  • Is the I/O main control board external chip plugged in?

12. Parameter error.

If the parameter is set incorrectly when modifying the parameter (this fault may be reported during synchronous vector control), the parameter error fault is reported.

Please modify the parameters again and press the reset button.

13. External failure.

When the local high voltage disconnect button is closed or the high voltage disconnect junction on the interface board is closed, the system will report an external fault.

Check whether the high voltage breakout button is pressed; whether the high voltage breakout terminal is shorted; whether the interface is bad.

14. High voltage power loss, the upper level of high voltage power disappears.

Usually caused by normal gate operation.

If there is an abnormally high voltage power failure (no-fault record, no switchgear operation), please check the opening circuit of the superior switch cabinet.

15. inverter over-current.

When the output current of the inverter exceeds 1.5 times the rated current of the inverter, the inverter will be over-current protected. You need to:

  • Check whether the output voltage board is normal and whether there is an obvious short circuit or discharge sign.
  • Whether the fiber is inserted tightly and the main circuit connection screws are tightened.
  • Whether the power supply to the Hall component is normal and the output current signal from the Hall component is correct.
  • Check that the parameter settings are not too short for acceleration time, too large for torque increase and too high for start-up frequency.
  • Whether the motor or load mechanism is blocked and whether the motor winding and output cable insulation are damaged.
  • Ensure that all units are in good working order (disconnect the unit from the copper strip and use a multi-meter or oscilloscope to check the unit input and output voltages and wave-forms for normal operation).
  • Whether the input supply voltage is too low.
  • On the output side of the inverter are power factor correcting capacitors or surge absorbers, which have the potential to cause resonance with the conductor.

So you need to eliminate the relevant devices and then check the unit detection board for shorts and damage.

If the above causes are still not correct, replace the controller signal board or main control board.

If the above causes are still not correct, replace the controller signal board or main control board.

In some sites, because of the effect of the tooth groove effect, the motor low-speed current fluctuation is very large, at this time the inverter may appear to limit the current, making the inverter accelerate, limit the current deceleration and other repeatedly, but not normal acceleration or cause over-current protection.

In this case, it is necessary to reduce the acceleration time and increase the current limiting factor to allow the motor to pass quickly through the fluctuating area and avoid over-current protection.

(In this case, remember to replace the unit if the output voltage of the unit is low).

16. Motor over-current.

The inverter output current is 1.2 times greater than the rated motor current and lasts for more than 2 minutes.

Please check whether the parameter setting motor rated current setting is correct; whether the motor or load machinery is blocked; whether the power supply voltage is too low.

17. The motor does not turn after the inverter is running.

Check the output of the inverter for contactors or switch-type equipment.

Check that the primary output cable of the inverter is connected to the motor.

Observe the monitor whether there are output current and output voltage, if there is voltage, no current means that the inverter to the main circuit of the motor is open, if there are voltage and current, then check whether the cable has a single-phase grounding, motor rotor winding is open.

18. Unit heavy failure.

There are 5 types of unit failure, including fuse failure, drive failure, unit overheating, unit over-voltage, fiber optic failure, where the first 3 types of failure can be bypassed (if the unit with bypass function, and the bypass level is set to non-0 when valid).

19. When a fuse fault is detected, the fuse fault is reported.

Please check if it is caused by the mains power outage; if the three-phase incoming wires of the unit are loose; if the incoming fuse is intact. If the fuse is open, replace the unit.

20. Drive failure.

Check whether the unit voltage detection board is short-circuited, if it is, will cause A1, B1 and C1 unit to report drive failure.

Is the power unit output L1, L2 short, otherwise the unit IGBT is damaged, please replace the unit.

Whether the insulation of the motor is in good condition.

Whether there is a mechanical failure of the load.

21. Unit overheating.

There is a temperature switch (normally closed point) on the radiator in the unit, when the temperature exceeds 85℃, the temperature relay normally closed point is disconnected, reporting the unit overheating fault.

Check whether the overhead fan is working properly, whether the unit cabinet fan switch is tripped, whether the filter screen is blocked (take a piece of A4 paper and put it on the filter screen to see if it can be adsorbed, otherwise you need to clean the filter screen).

Whether to work in a long-term overload condition, whether the ambient temperature is too high (the ambient temperature should be below 45 ℃, otherwise ventilation needs to be strengthened), wall-mounted ventilator, or roof-mounted air duct or install refrigeration equipment.

Whether the unit control board is bad and finally check the power unit temperature relay for normal.

22. Unit over-voltage.

The DC bus voltage exceeds the protection value and the inverter alarm unit is over-voltage.

When the inverter is in operation, if the output voltage of a unit is low, it will cause a three-phase output imbalance, and the reporting unit is over-voltage.

In no-load motor commissioning, it is easier to have DC bus over-voltage and A1/B1/C1 unit over-voltage, at this time, the reference voltage can be lowered appropriately.

Check that the input high voltage power supply does not exceed the permissible maximum (if the supply voltage is too high, the transformer taps can be adjusted to 105%).

If over-voltage occurs during deceleration, increase the deceleration time setting of the inverter appropriately.

23. Fiber failure

When the system fails to detect unit communication in the power-up state, a fiber fault is reported.

Whether the power unit control power supply is normal (when normal, the green light is on), otherwise replace the power unit; power unit and the controller’s fiber optic connector is disconnected, whether the fiber is broken.

24. Unit bypass

The unit is configured with bypass hardware, parameter settings in the bypass level is non-zero, if the unit has a drive fault, fuse fault, unit overheating these three failures, the unit bypass will occur.

If one unit fails and is bypassed, the other two units in the same position will be bypassed.

At this point, the inverter can still be started and operated, but the rated output voltage and rated capacity will be reduced due to the reduced number of units per phase in series.

When a unit bypass occurs, be sure to identify the cause and stop the unit as soon as possible to replace the faulty unit (the remaining two-phase bypassed unit does not need to be replaced).

Clean the unit driver board and unit control board, if these two boards are too thick to collect dust may cause false alarms.

25. The operating frequency is not consistent with the given frequency.

There are several reasons for this situation, the acceleration and deceleration process is limited by the acceleration and deceleration time and there is a process for the output frequency to reach a given frequency.

When the system voltage is too high, the frequency inverter can not stop at a numerical point to avoid DC bus over-voltage protection for its own protection.

At this point it is recommended that the transformer taps be connected to 105%.

The output current of the inverter exceeds the set current limit value, and the inverter automatically reduces the frequency to reduce the output current to avoid tripping the over-current protection.

This is usually the case when the input voltage is too low or the load increases abruptly; when a transient power failure occurs, the inverter automatically slows down to obtain energy from the motor in order to maintain the motor in a controlled state; or when a hall element, unit detection board or signal board fails.

26. Monitor the black screen.

Press the system reset button on the cabinet door (system reset does not affect the normal operating state of the inverter).

If it still cannot be recovered, then check whether the power terminal of the monitor is disconnected, whether the connection cable is loose, whether the 5V and 15V power supply is normal, whether the monitor line has obvious damage.

If there is interference, otherwise replace the monitor.

27. The parameters cannot be changed.

When the parameter modification option is set to disable in the function parameter, all parameters except this parameter and the given frequency or given parameter cannot be modified.

During operation, most of the parameters cannot be changed.

28. The inverter will restart automatically after shutdown.

In remote control mode, start and stop can only be done via the remote terminal.

If the start mode in the parameter setting is a level start (closed start, disconnected stop), the inverter will immediately stop freely if the emergency stop signal is disconnected during operation or the inverter is stopped by other means.

But when the emergency stop signal is closed again, because the remote start level signal is still present, the inverter will automatically start running.

29. The inverter will trip when it is powered up.

When the inverter is powered up, due to the transformer’s magnetic surge and unit capacitor charging, the instantaneous current RMS can reach up to 6-7 times the rated current of the inverter, the duration of several tens of milliseconds.

If the upper stage current protection setting value of the inverter is too small, it will cause the upper stage switch quick break protection trip.

You have to adjust the upper-level switch gear quick break protection setting.

30. The output frequency is oscillating at low speed during startup.

Some motors at low speed, because of the effect of the groove effect, the current fluctuation is very large, at this time the inverter may appear current limit, making the inverter repeated acceleration, current limit deceleration and other problems, but not normal acceleration.

In this situation, you have to increase the current limit setting; shorten start-up time; replace a unit when the output voltage is low.

31. The upper-level switchgear is tripped when the automatic bypass cabinet is automatically bypassed.

Check whether the time-delayed time absorption relay in the bypass cabinet is between 1.5S and 3S.

Whether the switchgear calibration value is too small (should be more than 5 times the motor’s rated current).

Set the quick break protection time of the switchgear to greater than 0.1S.

32. The external terminal has an induced AC voltage.

May be a remote start/stop, high voltage break, system reset signal line sensing voltage, it is recommended that the passive signal is wired separately from the 220V AC power supply, in this case it is best to use the shield wire both ends ground.

It may be the induced voltage caused by the signal cable on the remote control box and the power supply cable tied together, it is recommended to rewire the signal in the remote control box, it is best to use the shield wire for the signal without edge, and the shield wire stripping wire is not too long.

The 4-20mA current signal has an AC induced voltage (below 10V) and can be connected between the current signal and ground with a 275V/0.33uf.


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1 thought on “Inverter Troubleshooting: 32 Inverter Failure Causes and Solutions”

  1. ismail Abdullah

    hi, my 15kva 240v 3phase inverter is reading 10% in the red phase 90% in the yellow phase and 0% in the blue phase.
    that is before i load the inverter I don’t know what the problem is

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