(1) When restarting, it trips as soon as the speed increases. This is a very serious phenomenon of overcurrent. The main reasons are: load short-circuit, mechanical parts jam; inverter module damage; motor torque is too small, etc.;
(2) It will jump after power-on. Generally, this phenomenon cannot be reset. The main reasons are: bad module, bad drive circuit, bad current detection circuit;
(3) It does not trip immediately when restarting, but when accelerating. The main reasons are: the acceleration time setting is too short, the current upper limit setting is too small, and the torque compensation (V/F) setting is high.
①A LG-IS3-4 3.7kW inverter jumps "OC" as soon as it starts
Analysis and maintenance: Opening the cover did not find any signs of burnout. The online measurement of the IGBT (7MBR25NF-120) basically judged that there is no problem. To further judge the problem, after removing the IGBT, measure the turn-on and turn-off of the high-power transistors of 7 units. very good. When measuring the driving circuit of the upper half bridge, it was found that there was a clear difference between one path and the other two paths. After careful inspection, it was found that the output pin of an optocoupler A3120 was short-circuited with the negative pole of the power supply. After replacement, the three paths were basically the same. Everything is fine when the module is installed and powered on.
② When a BELTRO-VERT 2.2kW inverter is powered on, it will jump "OC" and cannot be reset.
Analysis and maintenance: First check the inverter module and no problems are found. Secondly, check the drive circuit and there is no abnormal phenomenon. It is estimated that the problem is not in this part. It may be in the part of the overcurrent signal processing. The circuit sensor is removed and then powered on. It shows that everything is normal. Therefore, the sensor is considered to be broken. Find a new one. After loading the test, everything is normal.
Overpressure (OU)
The over-voltage alarm usually occurs when the machine is stopped, and the main reason is that the deceleration time is too short or the braking resistor and braking unit are faulty.
A Taian N2 series 3.7kW inverter jumps "OU" when it stops.
Before repairing this machine, we must first understand the cause of the "OU" alarm. This is because when the frequency converter is decelerating, the speed at which the motor's rotor winding cuts the rotating magnetic field will increase, and the electromotive force and current of the rotor will increase, so that the motor is generating electricity. Status, the feedback energy flows to the DC link through the diode connected in parallel with the high-power switch tube in the inverter link, which causes the DC bus voltage to rise, so we should focus on checking the brake circuit, and there is no problem in measuring the discharge resistance. The tube (ET191) was found to have been broken down. After replacement, it was powered on and operated, and there was no problem with fast stopping.
Undervoltage (Uu)
Undervoltage 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: damage to a certain circuit of the rectifier bridge or abnormal operation of the three circuits of the thyristor may cause undervoltage faults Appears, secondly, the main circuit contactor is damaged, resulting in the loss of DC bus voltage, which may cause undervoltage on the charging resistor. There is also an undervoltage problem due to a failure of the voltage detection circuit
A CT 18.5kW inverter jumps on power up "Uu
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 completed by the use of thyristor but by the suction of the contactor During the charging process, it is believed that the fault may lie in the contactor or the control circuit and the power supply. Remove the contactor and add a 24V DC contactor to work normally. Then check the 24V DC power supply. After careful inspection, the voltage is output after the LM7824 zener tube is stabilized. It is measured that the zener tube is damaged. Find a new product and replace it and power on and work normally
A DANFOSS VLT5004 frequency converter
The display is normal after power-on, but "DC LINK UNDERVOLT" (DC link voltage is low) jumps after loading. This inverter is quite special in terms of phenomenon, but if you analyze the problem carefully, it will not be so complicated. The inverter also completes the charging process through the charging circuit and contactor. No abnormal phenomenon is found when it is powered on. It is estimated that it is caused by the voltage drop of the DC circuit when the load is applied, and the voltage of the DC circuit is full-wave rectified by the rectifier bridge and then provided by the capacitor after smoothing. Therefore, the rectifier bridge should be checked. The measurement found that the rectifier bridge has a The road bridge arm is open, and the problem is solved after replacing the new product
An ABB ACS500 22kW frequency converter
Jump "OH" after running for about half an hour. Because the fault occurs after a period of operation, the temperature sensor is unlikely to be damaged. Maybe the temperature of the inverter is indeed too high. After the power is turned on, it is found that the fan rotates slowly and the protective cover is full of cotton wool. After cleaning, the machine is turned on. The fan is running well and this fault has not been tripped after several hours of operation.
Unbalanced output
Unbalanced output generally manifests as motor jitter and unstable speed. The main reasons are: bad module, bad drive circuit, bad reactor, etc.
A Fuji G9S 11KW inverter, the output voltage difference is about 100V.
Turn on the machine and check the inverter module (6MBI50N-120) online. No problem is found. The 6-channel drive circuit is not found to be faulty. The module is removed and the measurement found that a high-power transistor of the road bridge cannot be turned on and off normally. The module has been Damaged, after confirming that the drive circuit is not faulty, everything is normal after replacing it with a new product.
overload
Overload is also one of the more frequent failures of the inverter. We should first analyze whether the motor is overloaded or the inverter itself is overloaded when seeing the overload phenomenon. Generally speaking, the motor has a strong overload capacity, as long as the motor is in the inverter parameter table. If the parameters are set properly, the motor overload is generally unlikely to occur. The inverter itself is prone to overload alarm due to its poor overload capacity. We can detect the output voltage of the inverter.
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