Analysis of the cause of IGBT explosion in the inverter

IGBT is the CPU of power electronic devices and plays a pivotal role in power electronic conversion and control. In the frequency converter, the IGBT module is more important. However, IGBT modules often explode. Below, the editor will analyze the case in detail.

1. IGBT Explosion

For some reason, the loss of the module is very large, and the heat cannot be dissipated, resulting in extremely high internal temperature, gas is generated, and the shell breaks through. This is the so-called IGBT explosion.

2. Analysis of IGBT Explosion Causes

1. The essence of the explosion is that the heating power exceeds the cooling power, and the internal cause should be overheating.

2. Human factors (1) The incoming line is connected to the outgoing line terminal (2) The inverter is connected to the wrong power supply (3) The load is not connected as required 3. Common reasons: (1) Overcurrent: one is a short circuit of the load, and the other The second is that the logic at the control circuit is disturbed, causing the upper and lower bridge arm components to pass through. (2) Insulation damage (3) Overvoltage: It is usually caused by the peak voltage generated by the stray inductance of the line under the action of extremely high di/dt. The solution is to design a high-performance absorption circuit to reduce the stray inductance of the line. (4) Overheating: The IGBT cannot be fully turned on, and the components are lost under the condition of the current

Increased temperature increases lead to damage. (5) Communication bit error rate a. After a period of communication, a sudden error message causes the IGBT to be misconducted and causes the IGBT to explode b. The FPGA program of the communication board runs unstable, causing the IGBT to misconduct and cause the IGBT to explode. 4 Other reasons (1) Overheating in the circuit The response time of the flow detection circuit cannot keep up.

(2) IGBT short-circuit protection is by detecting the saturation voltage drop, and the time left for the actuator is generally 10us (8 times overcurrent). When the power is turned on, it is easy to burn the pre-charging resistor and the IGBT in the braking unit.

(3) Technological problems: the alignment of the copper row is strong, the screws are not tightened, etc.

(4) Short-term high current: There are many reasons, such as the dead zone needs to be set properly, the main circuit is overvoltage, and the absorption circuit needs to be improved.

(5) The drive power supply is also a problem that should be paid special attention to. The isolation should be added to the isolation, and the filtering should be added to the filter.

(6) IGBT exploded due to excessive motor impact feedback voltage. But the probability of explosion during charging could be a lot higher.

(7) When the motor starts, the input voltage drops instantly, and the capacitor discharges. After the input measurement voltage is restored, the inrush current when the capacitor is charged is too large to cause the IGBT to explode 3. The case of the IGBT explosion

  Case number one

The inverter explodes when powered on, and the failure rate is about 5%. I suspected it was a problem with the charging circuit, but this old model has been used for a long time. Later, it was found that due to the use of a new factory, there was a problem with the power distribution of the new factory, and the grid voltage was unstable.

case two

When the frequency converter is powered on, the failure rate is about 2%. I have been trying to find the reason, and later found a strange phenomenon, the frequency converter is particularly easy to blow up on rainy days. In the end, the reason was that the PCB was not treated with moisture-proof treatment. On rainy days, there were water droplets on the PCB, and there was a problem with the insulation.

case three

The inverter was running well, but suddenly there was a loud noise, and the cabinet tripped. Its protection circuit was perfect, and it wasn't a wiring error, but two IGBTs exploded. The reason is the motor shock feedback voltage.

case four

Cause Analysis of IGBT Explosion in a Coal Chemical Group in Shaanxi

(1) The power supply line is short-circuited, and over-current and the insensitive over-current protection of the power unit is the main cause, and the over-voltage is the secondary cause.

(2) During the operation of the inverter, if one of the power units is damaged due to the huge moment of inertia of the fan motor, the energy will be suddenly and violently poured back, resulting in strong overcurrent and overvoltage. If the inverter is not protected in time, many of The IGBTs of two power units burn out simultaneously.

(3) If multiple large motors start simultaneously on the main fan 6KV power supply system, the power supply voltage of the inverter will drop instantaneously, and the energy stored in the intermediate capacitors of each power unit of the inverter will be exhausted instantly. When a strong surge current impact is generated, if the inverter is not protected in time, the IGBTs of multiple power units will be burned and explode simultaneously.