A converter for converting a multiple phase alternating input voltage waveform into a single phase alternating output voltage waveform, wherein the converter comprises: a) a bridge circuit having switching assemblies (1, 2, 3, 4, 5, 6) so connected as to define at least two pairs of input nodes and two output nodes (70, 80), each of the two pairs of input nodes being operative for receiving the input voltage waveform from one phase of a supply across the input nodes, and the output nodes (70, 80) being operative for providing a take-off point for the single phase alternating voltage output waveform, each switching assembly (1, 2, 3, 4, 5, 6) comprising at least two high power bi-directional semiconductor switching devices (SW A1, SW AN; SW B1, SW BN; SW C1, SW CN; SW D1, SW DN; SW E1, SW EN; SW F1, SW FN) connected in series between a respective input node and a respective output node to define a respective arm of the bridge circuit; b) a resonant circuit having a resonant frequency and connected across the output nodes (70, 80); and c) a control circuit for supplying a control waveform to each switching device (SW A1, SW AN; SW B1, SW BN; SW C1, SW CN; SW D1, SW DN; SW E1, SW EN; SW F1, SW FN) in the bridge circuit, the control circuit being operative for generating control signals which switch the switching devices (SW A1, SWAN; SW B1, SW BN; SW C1, SW CN; SW D1, SW DN; SW E1, SW EN; SW F1, SW FN) of the switching assemblies (1, 2, 3, 4, 5, 6) in each arm between on and off states in a pattern having a period substantially equal to the resonant frequency of the resonant circuit to provide the output waveform across the output nodes (70, 80) at a frequency which is substantially at the resonant frequency, and the resonant frequency being greater than a frequency of the multiple phase alternating input voltage waveform, the control circuit being operative for switching each device in the respective arm of the bridge circuit from the on state to the off state for one half cycle of a current in the resonant circuit, and from the off state to the on state for a remaining one half cycle, the switching being performed substantially at the resonant frequency of the resonant circuit. a) a bridge circuit having switching assemblies (1, 2, 3, 4, 5, 6) so connected as to define at least two pairs of input nodes and two output nodes (70, 80), each of the two pairs of input nodes being operative for receiving the input voltage waveform from one phase of a supply across the input nodes, and the output nodes (70, 80) being operative for providing a take-off point for the single phase alternating voltage output waveform, each switching assembly (1, 2, 3, 4, 5, 6) comprising at least two high power bi-directional semiconductor switching devices (SW A1, SW AN; SW B1, SW BN; SW C1, SW CN; SW D1, SW DN; SW E1, SW EN; SW F1, SW FN) connected in series between a respective input node and a respective output node to define a respective arm of the bridge circuit; b) a resonant circuit having a resonant frequency and connected across the output nodes (70, 80); and c) a control circuit for supplying a control waveform to each switching device (SW A1, SW AN; SW B1, SW BN; SW C1, SW CN; SW D1, SW DN; SW E1, SW EN; SW F1, SW FN) in the bridge circuit, the control circuit being operative for generating control signals which switch the switching devices (SW A1, SWAN; SW B1, SW BN; SW C1, SW CN; SW D1, SW DN; SW E1, SW EN; SW F1, SW FN) of the switching assemblies (1, 2, 3, 4, 5, 6) in each arm between on and off states in a pattern having a period substantially equal to the resonant frequency of the resonant circuit to provide the output waveform across the output nodes (70, 80) at a frequency which is substantially at the resonant frequency, and the resonant frequency being greater than a frequency of the multiple phase alternating input voltage waveform, the control circuit being operative for switching each device in the respective arm of the bridge circuit from the on state to the off state for one half cycle of a current in the resonant circuit, and from the off state to the on state for a remaining one half cycle, the switching being performed substantially at the resonant frequency of the resonant circuit.