Abstract: In apparatus for controlling the supply of power from an alternating current electrical supply of at least three phases to a resistive load, the load is so arranged that there exist current paths both between each phase connection of the load and two adjacent phase connections of the load and between each phase connection of the load and a common point which is directly connected to the neutral of the supply. The switching means for connecting each phase of the load to the corresponding phase of the supply is arranged to change from a non-conducting to a conducting state only when the voltage across such switching means is substantially zero, and to change from a conducting to a non-conducting state only when the current through each switching means is substantially zero.