Q.Write a note on the protection of power devices and converters.

Power devices and converters operate from the mains and face transients and faults, so several protection schemes, common to all devices, are built in against over-current, di/dt, over-voltage, dv/dt, over-temperature and gate stresses. …

[!TLDR]

Common protections: fuse+breaker (over-current), series inductor (di/dt), MOV (over-voltage), R-C snubber (dv/dt), heat sink (temperature), $R_G$ (gate over-current), zener $D_z$ (gate over-voltage).

Power electronic converters operate from the utility mains and are exposed to disturbances; transients from switching circuits and faults at the load stress the devices, so several protection schemes must be incorporated. These protection techniques are common to all power semiconductor devices. The devices and converters must be commonly protected against over-current, di/dt, voltage spikes/over-voltage, dv/dt, excessive temperature rise, gate over-current and gate over-voltage.

The protection methods are:

• Over-current: a semiconductor fuse, suitably selected and co-ordinated with fast circuit breakers connected in series with the device, protects against over-current.
• di/dt (maximum allowable rate of rise of current): limited by connecting a proper inductor in series with the device.
• Voltage spikes and over-voltages (large and of short duration): protected by Metal Oxide Varistors (MOVs) connected across the device.
• dv/dt (maximum allowable rate of rise of voltage): protected, for high stresses, by an R-C circuit (snubber circuit) across the device, chosen according to the device speed.
• Excessive case temperature: protected by mounting the device on a heat sink.
• Gate over-current: protected by a series resistance $R_G$ in the gate lead. …