When a load short circuit occurs in the IGBT of a frequency converter or a shoot-through occurs in the same bridge arm, the power supply voltage is directly applied between the collector and emitter terminals of the IGBT. The collector current flowing through the IGBT will increase sharply. If the gate drive signal is not removed quickly, the IGBT will burn out. The time that the IGBT can withstand the circuit current without damage is called the permissible short-circuit time.
To prevent IGBT damage due to short-circuit faults, OKE inverters have implemented a comprehensive fault detection and protection system. This system promptly detects overcurrent faults and quickly isolates them. Soft turn-off is employed to prevent excessively high voltage and current drop rates in di/dt, reducing protection operation delays. Slow turn-off by reducing the gate voltage within a limited time effectively minimizes the power and thermal stress impact of short-circuit protection on the IGBT, preventing induced overvoltage damage.
Short circuit protection is a device connected between a power source and a load that has the function of effectively disconnecting the short circuit point from the power source when a short circuit occurs on the load side.
Short-circuit breaking capacity refers to the ability of a device to reliably interrupt the short-circuit current without damaging the device itself after a short circuit occurs on the load side, thus preventing the fault range from expanding.
The main causes of short circuit faults are:
1) The cause of a shoot-through short circuit is the damage to a component in the bridge arm or the damage to the anti-parallel diode.
2) The cause of the bridge arm short circuit is that the two IGBTs in one bridge arm are turned on at the same time due to the fault of the control circuit or drive circuit or the malfunction caused by interference noise.
