Polyphase power converter circuits having a high frequency transformer link

Claim 2

A polyphase power converter circuit comprising the combination of a single phase high frequency linear transformer having a pair of inductively coupled windings, a first polyphase switching circuit including in each phase solid-state switching means effectively connected in series circuit relationship between one of said transformer windings and one of a set of first terminals in which appears a polyphase low frequency electric potential, a second switching circuit including a plurality of solid-state switching means each effectively connected in series circuit relationship with the other transformer winding and at least one of a set of second terminals, control means for synchronously rendering conductive at least one oF said solid-state switching means in each switching circuit for a predetermined interval of conduction, and for sequentially rendering conductive at least one of the other solid-state switching means in each switching circuit synchronously for a predetermined interval of conduction, said switching circuits being switched continuously in sequence at a switching rate which is relatively high as compared to the frequency of the polyphase electric potential appearing in said first terminals, whereby the polyphase low frequency electric potential is converted to a series of high frequency voltage pulses, transformed, and reformed at the second terminals with the desired waveform.

Claim 3

A circuit as defined in claim 1 further including filter capacitor means connected between said second terminals.

Claim 4

A circuit as defined in claim 1 wherein said first switching circuit is a three-phase circuit in which said solid-state switching means have bidirectional conducting characteristics and are wye-connected, and further includes filter capacitor means connected between said first terminals and other filter capacitor means connected between said second terminals.

Claim 5

A circuit as defined in claim 3 wherein said second switching circuit is a three-phase circuit in which said solid-state switching means are wye-connected.

Claim 6

A circuit as defined in claim 3 wherein said second switching circuit is in the form of a single phase rectifier.

Claim 7

A circuit as defined in claim 3 wherein said first polyphase switching circuit further includes series capacitor commutation means comprising commutating inductor means effectively coupled in series circuit relationship with commutating capacitor means and tuned to series resonance at a frequency greater than said switching rate for developing half sine wave current pulses and respectively commutating said solid-state switching means.

Claim 8

A polyphase power converter circuit comprising the combination of a single phase high frequency linear transformer having a pair of inductively coupled windings, a first polyphase switching circuit including in each phase bidirectional conducting solid state switching means effectively connected in series circuit relationship between one of said transformer windings and one of a plurality of first terminals in which appears a polyphase low frequency electric potential, a second switching circuit including a plurality of solid-state switching means each effectively connected in series circuit relationship with the other transformer winding and at least one of a plurality of second terminals, control means for continuously rendering conductive in sequence for approximately equal intervals of conduction, when the circuit conditions are appropriate, the solid-state switching means in the phases of said first polyphase switching circuit, and for synchronously rendering conductive at least one of said solid-state switching means in said second switching circuit, said control means operating to switch said switching means at a switching rate which is relatively high as compared to the frequency of the polyphase electric potential appearing in said first terminals, whereby the single phase high frequency transformer is time shared among the phases and the low frequency polyphase electric potential is converted to a series of high frequency voltage pulses, transformed, and reformed at the second terminals with the desired waveform. 8. A circuit as defined in claim 7 wherein said second switching circuit is a polyphase circuit with the same number of phases as said first switching circuit and includes in each phase at least one of said solid-state switching means, said second switching circuit solid-state switching means also having bidirectional conducting characteristics, and filter capacitor means connected between said second terminals to facilitate reforming of the low frequency polyphase electric potential at said second terminals.

Claim 9

A circuit as defined in claiM 7 wherein said second switching circuit is a single phase rectifier circuit and said second switching circuit solid-state switching means are unidirectional devices, and a filter capacitor connected between said second terminals.

Claim 10

A circuit as defined in claim 7 wherein said second switching circuit is a single phase rectifier circuit and said second switching circuit solid-state switching means are bidirectional conducting switching means, and a filter capacitor connected between said second terminals.

Claim 11

A three-phase power converter circuit comprising the combination of a single phase high frequency linear transformer having inductively coupled primary and secondary windings, a first three-phase switching circuit including in each phase bidirectional conducting solid-state switching means effectively connected in series circuit relationship between said primary transformer winding and one of a first set of terminals in which appears a three-phase low frequency electric potential, a second three-phase switching circuit including in each phase bidirectional conducting solid-state switching means effectively connected in series circuit relationship between said secondary transformer winding and one of a second set of terminals, filter capacitor means connected between said second terminals, control means for synchronously rendering conductive one of said solid-state switching means in each switching circuit for a predetermined interval of conduction, and for sequentially rendering conductive in sequence for approximately equal intervals of conduction another solid-state switching means in each switching circuit and finally the remaining solid-state switching means in each switching circuit, said control means operating to switch said pairs of switching means sequentially at a switching rate which is relatively high compared to the frequency of the three-phase electric potential appearing in said first terminals, whereby the single phase high frequency transformer is time shared among the phases and the low frequency three-phase electric potential is converted to a series of high frequency voltage pulses, transformed, and reformed at the second terminals as a three-phase electric potential.

Claim 12

A three-phase power converter circuit comprising the combination of a single phase high frequency linear transformer having inductively coupled primary and secondary windings, a first three-phase switching circuit including in each phase bidirectional conducting solid-state switching means effectively connected in series circuit relationship between said primary transformer winding and one of a first set of terminals in which appears a three-phase low frequency electric potential, a second three-phase switching circuit including in each phase bidirectional conducting solid-state switching means effectively connected in series circuit relationship between said secondary transformer winding and one of a second set of terminals, filter capacitor means connected between said second terminals, control means for synchronously rendering conductive one of said solid-state switching means in each switching circuit for a predetermined interval of conduction, and for sequentially rendering conductive in sequence for approximately equal intervals of conduction another solid-state switching means in each switching circuit and finally the remaining solid-state switching means in each switching circuit, said control means operating to switch said pairs of switching means sequentially at a switching rate which is relatively high compared to the frequency of the three-phase electric potential appearing in said first terminals, whereby the single phase high frequency transformer is time shared among the phases and the low frequency three-phase electric potential is converted to a series of high frequency voltage pulses, transformed, and reformed at the second terminals as a three-phase electric potential.

Claim 13

A circuit as defined in claim 11 wherein said first and second switching circuits further include series capacitor commutation means comprising commutating inductor means effectively connected in series circuit relationship with commutating capacitor means and tuned to series resonance at a frequency greater than said switching rate for developing half sine wave current pulses and respectively commutating said solid state switching means.

Claim 14

A circuit as defined in claim 11 wherein the phase rotation of sequentially switching said pairs of solid-state switching means is the same as the phase rotation of the low frequency three-phase electric potential in said first terminals.

Claim 15

A circuit as defined in claim 11 wherein the phase rotation of sequentially switching said pairs of solid-state switching means is different from the phase rotation of the low frequency three-phase electric potential in said first terminals.

Claim 16

A three-phase rectifier circuit comprising the combination of a single phase high frequency linear transformer having inductively coupled primary and secondary windings, a three-phase switching circuit including in each phase bidirectional conducting solid-state switching means effectively connected in series circuit relationship between said primary transformer winding and one of a first set of terminals in which appears a three-phase low frequency electric potential, a single phase rectifier switching circuit including at least a pair of alternately conducting solid-state switching means each effectively connected in series circuit relationship with the secondary transformer winding across a pair of second terminals, a filter capacitor connected between said second terminals, Control means for synchronously rendering conductive at least one of said solid-state switching means in each switching circuit for a predetermined interval of conduction, and for sequentially rendering conductive at least one of the other solid-state switching means in each switching circuit synchronously for a predetermined interval of conduction, said control means operating to switch said switching means continuously in sequence at a switching rate which is relatively high compared to the frequency of the three-phase low frequency electric potential in said first terminals, whereby the single phase high frequency transformer is time shared among the three phases and the low frequency three-phase electric potential is converted to a series of high frequency voltage pulses, transformed, and reformed at the second terminals as a unidirectional voltage.

Claim 17

A three-phase rectifier circuit comprising the combination of a single phase high frequency linear transformer having inductively coupled primary and secondary windings, a three-phase switching circuit including in each phase bidirectional conducting solid-state switching means effectively connected in series circuit relationship between said primary transformer winding and one of a first set of terminals in which appears a three-phase low frequency electric potential, a single phase rectifier switching circuit including at least a pair of alternately conducting solid-state switching means each effectively connected in series circuit relationship with the secondary transformer winding across a pair of second terminals, a filter capacitor connected between said second terminals, Control means for synchronously rendering conductive at least one of said solid-state switching means in each switching circuit for a predetermined interval of conduction, and for sequentially rendering conductive at least one of the other solid-state switching means in each switching circuit synchronously for a predetermined interval of conduction, said control means operating to switch said switching means continuously in sequence at a switching rate which is relatively high compared to the frequency of the three-phase low frequency electric potential in said first terminals, whereby the single phase high frequency transformer is time shared among the three phases and the low frequency three-phase electric potential is converted to a series of high frequency voltage pulses, transformed, and reformed at the second terminals as a unidirectional voltage.

Claim 18

A circuit as defined in claim 15 wherein said control means supplies turn-on signals to the solid state switching means in the phases of the three-phase switching circuit in a predetermined sequence and renders them conductive when the circuit conditions are appropriate.

Claim 19

A circuit as defined in claim 16 wherein the phase rotation of supplying turn-on signals to said three-phase switching circuit solid-state switching means is the same as the phase rotation of the three-phase low frequency electric potential in said first terminals.

Claim 20

A circuit as defined in claim 16 wherein the phase rotation of supplying turn-on signals to said three-phase switching circuit solid-state switching means is counter to the phase rotation of the three-phase low frequency electric potential in said first terminals.

Claim 21

A circuit as defined in claim 16 wherein said three-phase switching circuit further includes series capacitor commutation means comprising commutating inductor means effectively connected in series circuit relationship with commutating capacitor means and tuned to series resonance at a frequency greater than said switching rate for developing half sine wave current pulses and commutating said solid-state switching means.