The novice can solve the frequency converter common fault diagnosis and processing.(7)
1.8 the frequency converter is internally fired or burned
1.8.1 improper overvoltage absorption leads to ignition
Inverter in the fast switching current of frequency converter, found a master device is damaged, usually due to switching circuit inductance tend to exist, the magnetic energy stored in inductance will quickly turn into electric energy, especially when I was switching current is big, and distributed capacitance C small circuit, high during the current switcher terminal over-voltage u, sometimes up to several hundred volts, the voltage for kv, or even tens of thousands of volts.
Therefore, the over-voltage absorption circuit or device is set up at the C, E end of the power switch device (such as IGBT) of the frequency converter, D end of the switching power tube, and the power supply inlet end.But these protection device failure, or other devices with the same effect with bad performance (such as shoulder some of the overvoltage absorbing filter capacitance dry), are likely to occur overvoltage, flint, breakdown or protected switch device itself damaged.
When these absorbing elements are damaged and the printing plate on which they are installed is damaged, overvoltage, fire jumping, ablation and main components are immediately damaged.
When replacing these components, you need to be aware of the importance of the model. For example, the diode must use quick recovery or super fast recovery.
1.8.2 the damage of the main device causes ignition
Some frequency converters are damaged, which makes people wonder that a certain distance between the bus lines is not small, but there is a potential area of tip discharge, and there are signs of electric erosion.Careful inspection found that a main device was damaged, is it the result of insufficient spacing?No, this is because the main circuit has a certain inductance. When the main device burns down suddenly due to the short circuit and large current of the fault, the overvoltage between the bus lines will be caused (see figure 4).IGBT short circuit of inverter bridge switch device will cause the ignition between positive and negative bus lines.The short circuit of rectifying bridge or the inverse IGBT short circuit may cause the ignition at the incoming line or damage to the pressure-sensitive resistance used for the protection of the incoming line, because the incoming line also has inductance, which may also cause overvoltage.
When IGBT or rectifier bridge burns down, it will burst itself. In serious cases, it will damage surrounding devices, such as the drive circuit board.
1.8.3 pressure-sensitive resistance problem
Varistor is originally used to into the line side absorbed into line overvoltage protection device, but when the line voltage to continue higher, varistor performance changes, may make the varistor explosion destroyed, it could also have hurt around devices and wire insulation.
1.8.4 electrolytic capacitor leakage, explosion and combustion
The quality of electrolytic capacitance is poor, such as: liquid leakage, large leakage current, large loss, heat, drum, explosion cracking, combustion caused by explosion cracking, decreased capacity, increased internal resistance and inductance.The electrolytic capacitor used for filtering is easy to cause leakage, explosion and combustion due to high voltage, large capacity and large energy storage.Electrolyte is combustible and can cause combustion accidents.Use good quality electrolytic capacitors and replace them before reaching life.