Inverter failures (inverte Approach )

Posted by sere on February 28th, 2020

The structural composition of the inverter is mostly unitized or modularized. If the method is incorrect or incorrectly set during use, it may easily cause the inverter to fail and fail to achieve the expected operating results. Today, the editor of the inverter manufacturer introduces in detail the faults of the inverter and how to deal with them:

I. Over-voltage and under-voltage fault protection of the inverter

The most common reason for everyone to use the inverter is the overvoltage problem. The most common reason for the overvoltage problem is that the motor is in the power generation state, and the energy generated cannot be consumed in a timely manner. The most common cause of undervoltage is a phase loss in the power supply. Of course, the inverter manufacturershas corresponding protection functions, and its default response is OFF2 to stop.

The necessity of inverter over-voltage and under-voltage protection

The voltage detection circuit is an important part of the fault detection circuit of the inverter. In the inverter's main circuit, due to the withstand voltage of the rectifier bridge, IGBT filter capacitor and other components, the operating range of the device cannot be exceeded. , May cause the performance of the whole machine to decline, accelerated device aging, or even the situation of the bomber, so the voltage detection link is essential.

Third, the voltage detection principle

1. For the inverter's over-voltage and under-voltage protection circuits, it is generally designed on the DC side of the main circuit. According to the six-pulse rectification, the DC bus voltage is 1.35 times the AC incoming line voltage. The AC power supply can be reflected by detecting the DC bus voltage. .

2. In the main circuit, the series resistor divides the voltage, samples it to the CU for processing, and then calculates the DC bus voltage situation and responds accordingly. .

3. Through the voltage detection module, the monitoring of AC parameters can be realized.

Fourth, several factors that cause the inverter overvoltage fault.

1. Over-voltage problems caused by improper design selection:

① The potential energy load is decentralized, and no braking unit, braking resistor or energy feedback unit is not configured, which causes the DC bus voltage to increase until fault protection.

② The mechanical load itself is an "eccentric" mechanism. During the operation of the equipment, the motor will be dragged backwards, which will cause the inverter to overvoltage.

③ The cable on the output side of the inverter exceeds the allowed length of the inverter. Due to the influence of the distributed capacitance of the cable, the voltage reflection causes the inverter to overvoltage.

④ Unsuitable filter components are selected on the output side of the inverter, which will cause the inverter to overvoltage.

⑤ Switching device is installed on the output side of the inverter. During the operation of the inverter, the switch is operating.

2. Overvoltage problems caused by improper debugging:

① The motor deceleration time is set too short, which leads to overvoltage; due to the large mechanical inertia of some loads, if the deceleration time is too short, the frequency output by the inverter will fall rapidly, causing the actual speed of the motor rotor to be greater than the speed of the motor's rotating magnetic field. Working in the power generation state, the IGBT anti-parallel diodes of the inverter's main circuit feed back to the DC bus, causing the DC bus voltage to increase. If there is no braking unit or the power grid cannot be fed back, it will cause the DC bus voltage to increase. Eventually, Voltage failure.

② When the potential energy load is lowered, the timing of opening and closing the brake logic is not appropriate, resulting in overvoltage.

③ Rewinding and unwinding control technology. The unwinding motor is over-voltage due to being dragged back.

④During the operation of the high-power fan, the sudden change of the pipeline valve causes the inverter to overvoltage.

⑤ Belt conveyor control, speed setting is not suitable, and the over-voltage phenomenon of the towed motor inverter appears.

⑥ Multiple inverters and multiple motors drive a car at the same time, the speed setting is not appropriate, and the acceleration and deceleration times are inconsistent, resulting in inverter overvoltage.

最大 The function of the maximum DC voltage controller is prohibited. For example, during the inverter's speed reduction, if the inverter has an overvoltage trend, at this time, if the maximum DC voltage controller is activated, the inverter will automatically extend the speed reduction time and wait for DC. After the bus voltage returns to normal, the speed continues to decrease.

⑧The braking unit and braking resistor are installed in the hardware, but the braking resistor power P219 is not input, which is equivalent to the braking resistor not being turned on.

⑨Incorrect setting of motor nameplate data may also cause overvoltage.

3. Overvoltage problems caused by peripheral device failure:

① Power grid fluctuations or operating overvoltages caused by other equipment on the grid side.

② The motor insulation is damaged, and the winding grounding condition may cause overvoltage.

③ Loose cables and terminals on the output side of the inverter cause the inverter to overvoltage.

④ The filter on the output side of the inverter works abnormally, causing the inverter to overvoltage.

⑤ The motor drags a large inertial load. Before starting, the motor shaft rotates freely. During the speed-up process of the motor, the actual speed is higher than the synchronous speed, and the motor is in a feedback state, which causes overvoltage.

4. Overvoltage caused by inverter hardware problems:

① The voltage detection circuit is abnormal, causing overvoltage.

② The braking unit is damaged, the braking resistor is burnt out, and the braking resistor resistance selection is inappropriate.

③ Over-voltage fault caused by failure of inverter CU unit.

Five, under voltage fault protection

Usually the inverter reports an undervoltage fault, which is mostly caused by grid-side voltage fluctuations.

1. The AC grid voltage is low.

2. Under the same grid, large-capacity equipment is started.

3. The AC incoming line is out of phase, for example, a certain phase is fast-melted.

4. The trigger of the rectifier on the rectifier side is not good, and the rectifier bridge arm is damaged.

5. The DC electrolytic capacitor of the main circuit is aging, and the capacitance value decreases.

6. The voltage detection circuit is faulty and the undervoltage is caused.

7. The dynamic characteristics of the speed loop are adjusted too hard, or the acceleration time is too short, and the DC bus is pulled to the bottom instantly.