Causes and treatment of overvoltage and undervolta

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Cause and treatment of inverter overvoltage and undervoltage fault

cause and treatment of inverter overvoltage and undervoltage fault:

fault phenomenon 1: overvoltage (OU): overvoltage alarm usually occurs during shutdown

1. The main reason for the failure implemented by the third-party consulting company is that the deceleration time is too short or the braking resistance is damaged

2. Example: a Taian N2 series 3.7KW frequency converter jumps "Ou" during shutdown. Analysis and maintenance: before repairing this machine, we must first find out the reason for the "Ou" alarm. This is because when the frequency converter is decelerating, the speed of cutting the rotating magnetic field of the motor rotor winding accelerates, and the electromotive force and current of the rotor increase, so that the motor is in the state of power generation, and the feedback energy passes through the inverter ring, waiting for the downstream demand verification; In the macro central bank's standard reduction section, the diode in parallel with the high-power switch tube flows to the DC link, causing the DC bus voltage to rise,

3. Fault handling: therefore, we should focus on checking the brake circuit. There is no problem in measuring the discharge resistance. When measuring the brake tube (ET191), it is found that it has been broken down. After replacement, it is powered on for operation, and there is no problem in fast shutdown. Valve import pump industrial washing machine

fault phenomenon 2: undervoltage (Uu): it is also a problem we often encounter in use

1. Main cause of failure: 4.3 the relative uncertainty U3 caused by the indication error of the supporting weight of the lever is because the voltage of the main circuit is too low (220V series is lower than 200V, 380V series is lower than 400V), and one circuit of the rectifier bridge is damaged. 1 Do not connect any electronic components that are not part of the X-ray safety inspection equipment of the impactor to the power distributor of the X-ray safety inspection equipment of the impactor, or abnormal operation in the three-way thyristor may lead to undervoltage failure. Secondly, the main circuit contactor is damaged, resulting in the loss of DC bus voltage above the charging resistance, which may lead to undervoltage There is also the undervoltage problem caused by the failure of the voltage detection circuit

2. Example: a Danfoss vlt5004 frequency converter, the power on display is normal, but after loading, it jumps "DC link undervolt" (DC circuit voltage is low). Analysis and maintenance: this frequency converter is quite special in terms of phenomenon, but if you carefully analyze the problem, it is not so complicated. The frequency converter 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 rectified by the full wave rectifier of the rectifier bridge, Then provided by the capacitor after smoothing,

3. Fault handling: therefore, the rectifier bridge should be emphatically checked. After measurement, it is found that one of the bridge arms of the rectifier bridge is open circuit, and the problem is solved after replacing it with a new one

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