1 Over-current and over-current is the most frequent phenomenon of inverter alarm.

1.1 Phenomenon (1) When restarting, it trips at a rising speed. This is a very serious phenomenon of overcurrent. The main reasons are: load short circuit, mechanical parts stuck; inverter module damage; motor torque is too small and so on.

(2) Power-on jump, this phenomenon can not be reset generally, the main reasons are: bad module, bad drive circuit, bad current detection circuit.

(3) When restarting, it does not immediately trip, but when accelerating, the main reasons are: too short acceleration time setting, too low current limit setting, and high torque compensation (V/F) setting.

1.2 Example (1) An LG-IS3-43.7kW inverter jumps "OC" as soon as it starts

Analysis and maintenance: Open the cover and found no signs of burnout. On-line measurement IGBT (7MBR25NF-120) has no problem in basic judgment. To determine the problem further, turn off and turn off the IGBT after measuring 7 units of high-power transistors. well. When measuring the drive circuit of the upper half bridge, it was found that there was a clear difference between the two circuits and the other two circuits. After careful inspection, it was found that the output pin of the optocoupler A3120 was short-circuited to the negative terminal of the power supply. After the replacement, the three paths were basically the same. The module is powered on and everything is running fine.

(2) A BELTRO-VERT 2.2kW inverter energizes to jump “OC” and cannot be reset.

Analysis and maintenance: First check the inverter module found no problems. Secondly, there is no abnormality in checking the drive circuit. It is estimated that the problem is not in this block. It may be in the part of the over-current signal processing. After the circuit sensor is removed and the power is turned on, it shows that everything is normal. Therefore, the sensor is considered to be bad and a new one is needed. After loading the experiment, everything is normal.

2 Overvoltage Overvoltage alarms usually occur at the time of shutdown. The main reason is that the deceleration time is too short or there is a problem with the brake resistor and the brake unit.

(1) Example A Taian N2 series 3.7kW inverter jumps “OU” when it stops.

Analysis and maintenance: Before repairing this machine, we must first understand what causes the “OU” alarm. This is because when the frequency converter is decelerating, the rotor rotor winding cuts the rotating magnetic field faster, and the rotor's electromotive force and current increase. Make the motor in the power generation state, the energy returned by the diode in the inverter circuit in parallel with the high-power switch tube to the DC link, so that the DC bus voltage rise, so we should focus on checking the brake circuit, measuring the discharge resistance is no problem, When the brake pipe (ET191) was measured, it was found to have broken down. After the replacement, it was powered on, and there was no problem with the quick stop.

3 under-voltage under-voltage is also a problem we often encounter in use. Mainly because the main circuit voltage is too low (220V series is lower than 200V, 380V series is lower than 400V). The main reason is that any damage to the rectifier bridge or abnormal operation in the SCR three-way circuit may cause undervoltage faults. Appeared, followed by the main circuit contactor damage, resulting in DC bus voltage loss above the charging resistor may cause undervoltage. There is a voltage detection circuit failure and undervoltage problems.

3.1 Example (1) A Yamaguchi 18.5 kW frequency converter is powered on.

● Analysis and maintenance: After checking that the charging resistance of the rectifier bridge of this inverter is good, but no contactor action is heard after power-on, because the charging circuit of this inverter is not using thyristor but by the contactor. The suction process is completed to complete the charging process. Therefore, it is considered that the fault may be in the contactor or the control circuit and the power supply section. The removal of the contactor alone and the addition of the 24V DC contactor are working properly. Then check the 24V DC power supply, after careful inspection of the voltage is regulated by the LM7824 regulator after the output, measuring the regulator tube is damaged, find a new replacement after the power is working properly.

(2) For a DANFOSS VLT5004 inverter, the power-on display is normal, but jump “DCLINKUNDERVOLT” after the load (low DC loop voltage).

● Analysis and maintenance: This inverter is special in terms of phenomena, but if you carefully analyze the problem is not so complicated, the inverter also through the charging circuit, contactor to complete the charging process, there is no power Any abnormal phenomenon is estimated to be caused by the voltage drop of the DC circuit when the load is applied, and the voltage of the DC circuit is rectified by the full bridge of the rectifier bridge and then provided by the capacitor after the flat wave. Therefore, the rectifier bridge should be checked and measured. The rectifier bridge was found to have an open bridge and the problem was solved after replacing the new one.

54 Overheating Overheating is also a relatively common type of failure. The main causes are: high ambient temperature, blocked fans, poor temperature sensor performance, and motor overheating.

4.1 Example A customer of ABB ACS50022kW inverter reflected “OH” jumping about half an hour running.

● Analysis and maintenance: Because it is only after running for a period of time, there is a possibility that the temperature sensor is bad. The temperature of the inverter may be too high. After the power is turned on, the fan is found to be rotating slowly. The protective hood is full of a lot of cotton. (Because the frequency converter is used in the textile industry), the boot fan runs well after being cleaned, and does not jump this fault after several hours of operation.

5 Unbalanced output The unbalanced output is generally manifested as motor jitter, unstable speed, mainly due to bad module, bad drive circuit, and bad reactor.

5.1 An example of a Fuji G9S11KW inverter, the output voltage difference of about 100V.

● Analysis and maintenance: Open the machine to check the inverter module online (6MBI50N-120). No problem was found. Measured six drive circuits and found no faults. Remove the module and find that the high-power transistor on one side of the bridge cannot be turned on normally. Closed, the module has been damaged, after the replacement of new products after confirming that the drive circuit has no fault, everything is normal.

6 Overload overload is also one of the frequently occurring faults of the inverter. Usually, we see the overload phenomenon. In fact, we should first analyze whether the motor is overloaded or the inverter itself is overloaded. In general, the motor has strong overload capacity, as long as the inverter parameter table When the motor parameters are properly set, generally there will not be motor overload. The inverter itself is prone to overload alarm due to poor overload capacity. We can detect the inverter output voltage, current detection circuit, etc. .

6.1 Example A LGIH55KW inverter often jumps "OL" during operation.

● Analysis and maintenance: According to customers, this machine was originally used on a 37kw motor and is now switched to a 55kw motor. The parameters have not been re-set, so the problem may be in the parameters, after checking the inverter current limit is set to 37kw motor rated current, after the parameters are reset and all the normal load

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