Inverter inverter module damage troubleshooting skills

The damage of the inverter inverter module is mostly caused by the damage of the drive circuit, causing the two switching devices on one bridge arm to be turned on at the same time. Inverter inverter power module damage is a common fault in other frequency conversion equipment such as vector inverter or energy-saving inverter. To solve this problem, only the root cause of damage can be found, and the possibility of damage again can be eliminated first. Change the module, otherwise the new module will be damaged again.

First, judge the inverter power module mainly has IGBT, IPM, etc., check whether the appearance has exploded, whether the terminal and the connected printed board have ablation marks. Use a multimeter to check whether CE, GC, GE are connected, or use a multimeter to measure whether P, U, V, W, and N have U, V, and W resistance inconsistencies, and the control poles of each driving power device are U, V, W, Whether the resistances of P and N are inconsistent, to determine which power device is damaged.

Second, the cause of damage

(1) The quality of the device itself is not good.

(2) The external load has severe overcurrent and unbalance. The winding of one phase of the motor is short-circuited to the ground. There is a phase short circuit internal short circuit, the load is mechanically stuck, the phase is broken, and the output wire is short-circuited or short-circuited to the ground.

(3) The capacitor is connected to the load, or the capacitor is too large due to improper wiring, so that the power tube has an inrush current.

(4) The user's grid voltage is too high, or there is a strong transient overvoltage, causing overvoltage damage.

(5) The overvoltage absorbing circuit of the power switch tube in the machine is damaged, which may not effectively absorb the overvoltage and damage the IGBT, as shown in the figure below.

Inverter inverter module damage troubleshooting skills

(6) The filter capacitor is aged for a long time, the capacity is reduced or the internal inductance is increased, and the overvoltage absorption capability of the busbar is lowered, causing the overvoltage on the busbar to be too high and damaging the IGBT. In the normal operation, the overvoltage on the busbar is converted from the inductive energy storage of the busbar circuit when the inverter switching device is turned off.

(7) The front-end opto-isolated device of the IGBT or IPM power device is broken down due to breakdown, or the ignition of the printed circuit board is caused by dust and moisture, resulting in damage to the IGBT and IPM.

(8) Inappropriate operation, or defective in the product design software, causing the simultaneous switching of the upper and lower power switching devices at the same time in the unstable situation such as interference and power-on and shutdown.

(9) Lightning strikes, house leaks, foreign objects entering, inspectors accidentally touching and other accidents.

(10) The filter capacitor has been replaced by maintenance. Because the quality of the capacitor is not good, or the line connected to the capacitor is longer than the original, the inductance is increased, resulting in a significant increase in the overvoltage of the bus.

(11) The front-stage rectifier bridge is damaged, and the IGBT and IPM are damaged due to the AC power entering the front stage of the main power supply.

(12) Repair and replacement of the power module, because there is no static protection measures, the IGBT is damaged during the welding operation. Or due to poor handling, such as heat dissipation, fastening, and insulation during repair, it may cause damage due to short-term use.

(13) The IGBT is used in parallel, and the consistency of the model and batch number is not considered in the replacement, resulting in uneven current and damage of the parallel components.

(14) A component of the internal protection circuit (overvoltage, overcurrent protection) of the inverter is damaged and loses its protection function.

(15) A certain group of power supplies inside the inverter, especially the IGBT driver stage +, - power supply is damaged, the output value is changed or the insulation between the two groups of power supplies is broken.

Third, the replacement only finds the root cause of the damage, and first eliminate the possibility of damage again, in order to replace the inverter module, otherwise the new module will be damaged.

(1) IGBTs should be protected from electrostatic damage as well as insulated gate field effect transistors. The fundamental measure to prevent damage during assembly welding is to connect all the machines to be repaired, IGBT modules, soldering irons, people, operating table pads, etc., so that the operation is performed at the same electric field potential, and all connections are common. It is better if the point can be grounded. In particular, the power supply iron head can not be equipped with high-potential power supply, and the oscilloscope power supply should be isolated by a well-isolated transformer. The IGBT module must keep the control electrode G and the emitter E connected before it is used. Do not remove the anti-static protection GE connection measures of the device before leaving the factory.

(2) Apply thermal grease between the power module and the heat sink to ensure the thickness of the coating is 0.1 0.25mm, the contact surface is more than 80%, and the tightening torque is applied according to the size of the fastening screw (M4 13kg?cm, M5 17kg?cm, M6 22kg) ?cm) to ensure that the module is well cooled.

(3) When the machine is disassembled, take notes on the removed parts, thread ends, and parts. All kinds of technical measures on the original assembly should be handled during reassembly, and should not be simplified or omitted. For example, the input twisted pair, the resistance value of each electrode connection, the insulation, the absorption plate or the absorption capacitance should be maintained as they are; the cleaning of the soldered printed circuit board should be cleaned and the paint protection should be prevented. And to ensure reliable insulation, not to wear less and misplaced parts.

(4) Parallel modules require the same model and number. When the numbers cannot be consistent, ensure that all modules connected in parallel have the same performance.

(5) For the copper parts that are caused by the bomber, the burrs should be rounded to avoid damage due to over-voltage discharge.

4. After the module is replaced, the power is often replaced after the module is replaced. In order to prevent such accidents, a resistor is generally connected in the DC main circuit of the inverter. The resistance is 1 y 2 赘 and the power is 50 W or more. Due to the current limiting action of the resistor, the module will not be damaged even if the fault is turned on. When the current is idling, the current flowing through the resistor is small, and the voltage drop is also small, and the no-load inspection can be performed. Generally, as long as the no-load operation is normal, the removal of the resistor will be normal.

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