Consideration has been given to the use of a static switch as a switch for switching between electrical connection and disconnection between an alternating-current power supply and a load. For a static switch, a thyristor switch is typically used that is constituted of a pair of thyristors connected in anti-parallel.
For example, Japanese Patent Laying-Open No. 55-103073 (PTD 1) discloses a thyristor switch that has anti-parallel connected thyristor arms, each constituted of a plurality of thyristors connected in series, and that is configured to supply alternating power to a load through the pair of thyristor arms connected in anti-parallel. In PTD 1, in response to a gate signal applied to the thyristor arms, the plurality of thyristors are turned on and a load current is allowed to flow. Thus, the load is supplied with alternating power. In this state, in response to interruption of the gate signal, the plurality of thyristors are turned off and the load current comes to zero. Thus, the power supply to the load is interrupted.