selfcommutate

Self-commutation, or self-commutate, is a concept in power electronics describing the ability of a switch to turn off current through its own action rather than relying on the external circuit or the AC supply to interrupt the current. It is most closely associated with devices that can be gated on and off by control signals, such as insulated-gate devices, and with switching converters that use these devices.

In a self-commutating arrangement, the device is turned on by a gate signal and turned off by reducing the gate drive or by using a commutation circuit that drives the current to zero. This enables controlled interruption at will, independent of the voltage waveforms of the supply. This is in contrast to line-commutated devices, such as conventional thyristors, which rely on the AC line’s natural current zero crossing to turn off.

Self-commutation enables fully controlled rectification and inversion, supports higher switching frequencies, and is fundamental to modern DC power electronics, including motor drives, switched-mode power supplies, and HVDC converters. The approach reduces dependence on the AC line for turn-off, but it requires appropriate gate drive electronics, isolation, and effective thermal management due to switching losses and switching stress.

Common self-commutated devices include insulated-gate transistors such as IGBTs and MOSFETs, which can be switched on and off by gate signals in suitable topologies. In practice, many contemporary power-electronics systems rely on self-commutated devices to achieve fast, precise control, while some applications still use line-commutated topologies where suitable.