A.C. supply converter

Claim 2

A direct a.c. converter having N input conductors for an N-phase a.c. input voltage system, where N is an odd integer greater than 2, one or more output conductors for carrying respective phases of an a.c. output voltage system having at least one characteristic such as frequency, amplitude, phase angle or phase displacement which is different from that of the input voltage system, a plurality of bidirectional switches which individually connect each input conductor to the or each output conductor, and a control system including timing means which produces for the or each output conductor a repeating sequence of mutually abutting width modulated pulses, there being N pulses in the sequence respectively allocated to the phases of the input voltage system, the control system being connected to the switches so that the pulses cause the switches to be closed in such a way that each phase of the input voltage system is connected in turn to the or each phase of the output voltage system and that at any given instant only one of the switches connected to the or each output conductor is closed, wherein the width modulation of the pulses includes a component at the N th harmonic of the input voltage frequency which is of such an amplitude and so phased as to permit the amplitude of the output voltage system to be larger than the minimum instantaneous voltage of the input voltage system.

Claim 3

A converter according to claim 1, wherein the phase of the harmonic component is such that its peaks coincide with the peaks of the N phases of the input voltage system.

Claim 4

A converter according to claim 1 wherein N is 3 and the amplitude of the harmonic component is one quarter that of the input voltage system.

Claim 5

A direct a.c. converter having N input conductors for an N-phase a.c. input voltage system, P output conductors for carrying respective phases of a polyphase a.c. output voltage system having at least one characteristic such as frequency, amplitude, phase angle or phase displacement which is different from that of the input voltage system, where P is an odd integer greater than 2, a plurality of bidirectional switches which individually connect each input conductor to each output conductor, and a control system including timing means which produces for each output conductor a repeating sequence of mutually abutting width modulated pulses, there being N pulses in the sequence respectively allocated to the phases of the input voltage system, the control system being connected to the switches so that the pulses cause the switches to be closed in such a way that each phase of the input voltage system is connected in turn to each phase of the output voltage system and that at any given instant only one of the switches connected to each output conductor is closed, wherein the width modulation of the pulses includes a component at the P th harmonic of the output voltage frequency which is of such an amplitude and so phased as to permit the amplitude of the output voltage system to be larger than the minimum instantaneous voltage of the input voltage system.

Claim 6

A direct a.c. converter having N input conductors for an N-phase a.c. input voltage system, P output conductors for carrying respective phases of a polyphase a.c. output voltage system having at least one characteristic such as frequency, amplitude, phase angle or phase displacement which is different from that of the input voltage system, where P is an odd integer greater than 2, a plurality of bidirectional switches which individually connect each input conductor to each output conductor, and a control system including timing means which produces for each output conductor a repeating sequence of mutually abutting width modulated pulses, there being N pulses in the sequence respectively allocated to the phases of the input voltage system, the control system being connected to the switches so that the pulses cause the switches to be closed in such a way that each phase of the input voltage system is connected in turn to each phase of the output voltage system and that at any given instant only one of the switches connected to each output conductor is closed, wherein the width modulation of the pulses includes a component at the P th harmonic of the output voltage frequency which is of such an amplitude and so phased as to permit the amplitude of the output voltage system to be larger than the minimum instantaneous voltage of the input voltage system.

Claim 7

A converter according to claim 4, wherein the phase of the harmonic of the output voltage frequency is such that its peaks coincide with the peaks of the P phases of the output voltage system.

Claim 8

A converter according to claim 4 wherein P is 3.

Claim 9

A direct a.c. converter having N input conductors for an N-phase a.c. input voltage system, where N is an odd integer greater than 2, P output conductors for carrying respective phases of a polyphase a.c. output voltage system having at least one characteristic such as frequency, amplitude, phase angle, or phase displacement which is different from that of the input voltage system, where P is an odd integer greater than 2, a plurality of bidirectional switches which individually connect each input conductor to each output conductor, and a control system including timing means which produces for each output conductor a repeating sequence of mutually abutting width modulated pulses, there being N pulses in the sequence respectively allocated to the phases of the input voltage system, the control system being connected to the switches so that the pulses cause the switches to be closed in such a way that each phase of the input voltage system is connected in turn to each phase of the output voltage system and that at any given instant only one of the switches connected to each output conductor is closed, wherein the width modulation of the pulses includes components at the N th harmonic of the input voltage frequency and the P th harmonic of the output voltage frequency, the components being of such amplitudes and so phased as to permit the amplitude of the output voltage system to be larger than the minimum instantaneous voltage of the input voltage system.

Claim 10

A direct a.c. converter having N input conductors for an N-phase a.c. input voltage system, where N is an odd integer greater than 2, P output conductors for carrying respective phases of a polyphase a.c. output voltage system having at least one characteristic such as frequency, amplitude, phase angle, or phase displacement which is different from that of the input voltage system, where P is an odd integer greater than 2, a plurality of bidirectional switches which individually connect each input conductor to each output conductor, and a control system including timing means which produces for each output conductor a repeating sequence of mutually abutting width modulated pulses, there being N pulses in the sequence respectively allocated to the phases of the input voltage system, the control system being connected to the switches so that the pulses cause the switches to be closed in such a way that each phase of the input voltage system is connected in turn to each phase of the output voltage system and that at any given instant only one of the switches connected to each output conductor is closed, wherein the width modulation of the pulses includes components at the N th harmonic of the input voltage frequency and the P th harmonic of the output voltage frequency, the components being of such amplitudes and so phased as to permit the amplitude of the output voltage system to be larger than the minimum instantaneous voltage of the input voltage system.

Claim 11

A converter according to claim 7, wherein the phase of the N th harmonic component is such that its peaks coincide with the peaks of the N th harmonic of the input voltage system.

Claim 12

A converter according to claim 7 wherein N is 3 and the amplitude of the N th harmonic component is one quarter that of the input voltage system.

Claim 13

A converter according to claim 7, wherein the phase of the P th harmonic of the output voltage frequency is such that its peaks coincide with the peaks of the P th harmonic of the output voltage system.

Claim 14

A converter according to claim 7, wherein P is 3 and the amplitude of the P th harmonic component is 0.192 of that of the output voltage system.

Claim 17

A method according to claim 12 in which the output voltage system has P phases, where P is an odd integer greater than 2, wherein the width modulation of the samples also includes a component at the P th harmonic of the output system frequency which is of such amplitude and phase as to permit the amplitude of the output voltage system to be larger than it could be if the component were absent.