Frequency conversion power supply repair method - Solutions - Huaqiang Electronic Network

Filter 18.432M

1 Damage to the inverter power module
1.1.1 Judging the inverter power module mainly includes IGBT, IPM, etc., check whether the appearance has exploded, and whether the terminal and the connected printed board have ablation marks. Use a multimeter to check whether CE, GC, and GE are connected, or use a multimeter to measure whether P, U, V, W, and N have inconsistent U, V, and W resistances, 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.
1.1.2 Reason for 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, so that the IGBT cannot be effectively absorbed and the IGBT is damaged, as shown in Fig. 1.
(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 is replaced by maintenance. Because the quality of the capacitor is not good, or the line connecting 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 inverter's internal protection circuit (overvoltage, overcurrent protection) 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.
1.1.3 Replacement Only find 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 again.
(1) IGBTs should avoid 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 from 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 0.25 mm, the contact surface is more than 80%, and the tightening torque is applied according to the size of the fastening screw (M4 13 kg·cm, M5 17 kg· Cm, M6 22 kg·cm) to ensure good heat dissipation of the module.
(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 defects of the copper parts caused by the bomber, the burrs should be rounded and sanded to avoid damage caused by the tip discharge of the overvoltage.

When the IGBT is normally turned on, its saturation voltage drop is very low. When the IGBT is over-current, the tube voltage drop VCE will increase with the increase of the short-circuit current. When it increases to a certain value, the detection diode VDB will reverse-conduct. The reverse current signal is sent to the CPU processor via the IGBT drive protection circuit, and the CPU blocks the IGBT output for protection. If the detection diode VDB is damaged, the ECO15 inverter will have an ER15 fault, and the detection diode can be replaced during field processing to eliminate the fault.
1.10.6 Fault ER11
The ER11 fault of the variable frequency power supply indicates that the inverter is overheated. The possible causes are: air duct obstruction, high ambient temperature, failure of the cooling fan, and abnormal temperature detection circuit. When the site is processed, it is first determined whether the inverter is over-temperature. If the temperature is too high, the fault can be eliminated according to the above reasons; if the ER11 alarm occurs under normal temperature, the fault is caused by the temperature detection circuit. The seven-unit inverter module used in Kangwo's 22 kW models has integrated temperature components. If this part of the module also has ER11 alarms, the same fault phenomenon will occur when the temperature detection circuit is abnormal.
2 Frequently Asked Questions and Solutions for Inverter Drive Circuits Over the past 10 years, with the infiltration of power electronics technology, microelectronics technology and modern control theory into the field of AC electric drive, variable frequency AC speed regulation has gradually replaced the past slip rate adjustment. Speed ​​control technology such as speed, variable pole speed regulation and DC speed regulation. It can be said that there is a frequency converter in the place where there is an AC motor. Its main features are high efficiency of drive performance and good control characteristics.
The general-purpose inverter generally includes the following parts: a rectifier bridge, an inverter bridge, an intermediate DC circuit, a precharge circuit, a control circuit, a drive circuit, and the like. The quality of a frequency converter, the drive circuit plays a vital role, now let's talk about the common problems of the drive circuit and the solution.
With the continuous development of technology, the drive circuit itself has experienced from the drive circuit of the pin type component to the optocoupler drive circuit, to the thick film drive circuit, and the relatively new integrated drive circuit. At present, the latter three types of drive circuits are often encountered in maintenance.
The following describes how to repair several drive circuits.

1 The cause of the damage of the drive circuit and the cause of the drive damage are various. Generally speaking, the problem is nothing more than U, V, W three-phase no output or output imbalance, or output balance but at low frequency Time jitter, as well as start alarms. When the fast fuse of a variable frequency power supply large capacitor is disconnected, or the IGBT inverter module is damaged, the drive circuit is basically impossible to be intact, and it is not necessary to replace it with a good fast fuse or IGBT inverter module. This can easily cause the new device that has just been replaced to be damaged again. At this time, it should be emphasized whether there is a mark on the drive circuit. You can first unplug the drive pin of the IGBT inverter module and measure whether the resistance of the 12-way drive is the same with a multimeter. If the 12-channel resistance is basically the same, it can not fully prove that the driving circuit is intact. Then, it is necessary to use an electronic oscilloscope to measure whether the voltages on the six-way driving circuit are the same. When the starting signal is given, the waveforms of the 12-way driving circuit are the same. If you don't have an electronic oscilloscope, you can also try to use a digital electronic multimeter to measure the DC voltage of the drive circuit. Generally speaking, the DC voltage on each drive circuit when starting is about 10 V, and the DC voltage after starting is 2-3 V. If the measurement result is normal, it is basically judged that the drive circuit of the inverter is good. of. Then connect the IGBT inverter module to the drive circuit, but remember that in the absence of 100% confidence, the safest method is to disconnect the P of the IGBT inverter module from the DC bus, and connect a group of bulbs in the middle or A higher power resistor, which protects the IGBT inverter module from being burnt out by the large capacitor discharge current in the event of a large current in the circuit. The following are some examples of the drive circuit involved in repairing the drive.
2
The fault phenomenon is the three-phase output voltage, and it always alarms after starting, and normal operation cannot be performed. Firstly, it is estimated that most of the inverter drive circuit is damaged. The correct solution should be to turn off the variable frequency power supply after determining the fault phenomenon, remove the IGBT inverter module from the printed circuit, and use an electronic oscilloscope to observe whether the waveform of the six-way drive circuit is open. Consistently, find out the inconsistent drive circuit and replace the optocoupler on the drive circuit. If the inverter power supply is used for more than 3 years, it is recommended to replace all the electrolytic capacitors of the drive circuit, and then observe with the oscilloscope. After the agreement, the IGBT inverter module is installed to carry out the load test and the phenomenon is eliminated.