This guide applies to self-commutated electronic power converters in which commutation is accomplished by components within the converter. In converters using switching devices that have turn-off capability, such as transistors or gate turn-off thyristors, interruption of the current results in a voltage that commutates the current to another branch. In converters using circuit-commutated thyristors, the commutating voltages required to transfer current from one branch to another are normally supplied by capacitors. The type of power conversion may be DC to AC, DC to DC, AC to DC, or AC to AC. Converters in which commutating voltages are supplied by the AC lines, the AC load, or some other AC source outside the converter, are excluded from the scope of this guide except where they may be linked with a self-commutated converter.<>