company news

Main circuit tripping

This kind of fault manifests itself as a loud noise during the operation of the inverter, or failure to supply power when starting up, and the circuit breaker or air switch used for controlling the inverter trips. This situation is generally caused by a direct breakdown and short circuit of the main circuit (including the rectifier module, electrolytic capacitor or inverter bridge). At the moment of breakdown, a strong and large current causes the module to burst and produce a loud noise.

  There are many reasons for module damage and it is not easy to generalize. Now we only list a few types of situations encountered.

1) Damage to the rectifier module is mostly caused by pollution of the power grid. Due to the use of controllable rectifiers (such as silicon controlled welders, motorcycle charging bottles, etc.) in the frequency converter control circuit, the waveform of the power grid is no longer a regular sine wave, causing the rectifier module to be damaged by pollution from the power grid, which requires enhanced frequency conversion. The power absorption capacity of the input terminal of the converter.

2) Damage to electrolytic capacitors and IGBTs is mainly caused by uneven voltage equalization, which includes dynamic voltage equalization and static voltage equalization. In an inverter that has been used for a long time, due to the reduction of the capacity of some capacitors, the entire capacitor group will have uneven voltage, and the capacitors with high shared voltage will definitely burst. The damage to the IGBT is mainly caused by the excessive peak voltage of the busbar and the inability of the buffer circuit to absorb it. During the IGBT turn-on and turn-off process, there is a very high current change rate. When the busbar design is unreasonable and the busbar inductance is too high, the voltage borne by the module will be too high and breakdown will occur. The instant of breakdown will be large. The current causes the module to explode, so reducing the bus inductance is the key to making a good inverter.

3) Another one is that the parameter settings are unreasonable. Especially under large inertia loads, such as centrifugal fans, centrifugal mixers, etc., because the frequency converter frequency decreases for too short a time, the motor generates electricity during the shutdown process and the bus voltage rises, exceeding the limit that the module can withstand and bursting. In this case, the drop time should be made as long as possible, generally not less than 300 seconds, or a leakage circuit should be added to the main circuit and a energy-consuming resistor should be used to release the energy.