Identify Damaged Inverter Filter Electrolytic Capacitors

Inverter filter electrolytic capacitor is considered to be damaged? Actually, the outer plastic casing is cracked, the aluminum shell bulging, the appearance of explosion, out of the electrolyte, the insurance valve is opened or pressed out, the capacitor part of the valve cracking, wiring The column is heavily rusted, and the cover plate is deformed or peeled off. This indicates that the electrolytic capacitor is damaged and cannot be used. At this time, the multimeter is used to measure the open circuit or short circuit, the capacity is obviously reduced, and the leakage is serious (the resistance after the final stability is measured by a multimeter is small).

Analysis of Causes of Capacitor Damage:

1. The rectifier bridge before the filter is damaged, and AC power directly enters the capacitor.

2. The heat radiation environment is not good, so that the temperature rise of the capacitor is too high, and it will be damaged for a long time.

3. The voltage divider resistance is damaged, and the partial pressure unevenness causes a certain capacitor to break down first, followed by the breakdown of other related capacitors.

4. The quality of the device itself is not good (large leakage current, large loss, low pressure resistance, impurities such as chloride ions, poor structure, and short life).

5. The poor installation of capacitors, such as outsourcing insulation damage, the shell connected to the potential of the electrical connection and the welding site is not good, resulting in poor contact and heat damage.

How to replace the capacitor:

1) It is better to replace the filter electrolytic capacitor with the same model as the original one. When the same model cannot be obtained at the same time, the following points must be noted: The withstand voltage, leakage current, capacity, size, polarity, and installation method should be the same and Choose a product that can withstand large ripple currents and long life.

2) During the process of replacement and disassembly, note that the electrical connection (screw connection and welding) is firm and reliable, and the positive and negative electrodes must not be connected incorrectly. The fixing clamp should be firmly fixed, and the external insulation sheath of the capacitor must not be damaged. The partial pressure resistance is connected as it is. , And measure the resistance value, should make the partial pressure even.

3) Electrolytic capacitors that have been placed for more than one year should be measured for leakage current. They must not be too large. Before loading, they should be subject to DC current aging. The DC current should be increased first. When the leakage current decreases, the voltage is increased. Finally, the rated voltage is increased. The leakage current must not exceed the standard value.

4) Since the size of the capacitor is not suitable and the replacement capacitor can only be installed in other positions, care must be taken that the bus from the inverter module to the capacitor cannot be longer than the original busbar. The area enclosed by the two + and - busbars must be as large as possible. Small, the best way to use twisted pair. This is because the capacitance connection bus extension or +, - busbar envelopment area assembly causes the busbar inductance to increase, causing a pulse overvoltage rise on the power module, resulting in damage to the power module or overvoltage absorbing device. In the last resort, another high frequency and high voltage surge absorbing capacitor is added to the inverter module with a short line to help absorb the overvoltage of the bus and compensate for the damage caused by the extension of the capacitor connection bus.