Inverter provided with an overvoltage clamping circuit

Claim 2

An overvoltage suppressing apparatus, comprising: a voltage source inverter having switching transistors, recirculating diodes connected across current paths of the switching transistors, and an output terminal; at least one reactor having an input terminal connected to the output terminal of said voltage source inverter and an output terminal to be connected to the primary side of a boosting transformer; a clamping circuit including a diode for clamping an output voltage at the output terminal of said reactor to a first predetermined potential so that a potential on said output terminal of said reactor does not exceed said first predetermined potential; and at least one capacitor having one end connected to the output terminal of said reactor and another end coupled to a second predetermined potential, said capacitor and said reactor forming a resonant circuit which limits changes in potential between said first and second predetermined potentials on said output terminal to a resonance curve defined by said resonant circuit.

Claim 3

An overvoltage suppressing apparatus according to claim 1, including plural reactors, wherein said input and output terminals of said reactors are formed at each one end and each of the other ends of said reactors, respectively.

Claim 4

An overvoltage suppressing apparatus, comprising: a DC power source; a three-phase voltage source inverter having DC power input terminals connected to the DC power source and having three output terminals; three reactors having input terminals connected to respective of the output terminals of the voltage source inverter and taps provided as output terminals for connection to the primary side of a boosting transformer; a clamping circuit including three diodes for clamping the three output terminals of said reactors to a first predetermined potential so that the respective potentials on said output terminals of said reactors do not exceed said first predetermined potential; and three capacitors each having one end connected to one of the output terminals of said reactors and another end coupled to a second predetermined potential, said capacitors and said reactors forming resonant circuits which limit changes in potential between said first and second predetermined potentials of said output terminals to a resonance curve defined by said resonant circuits.

Claim 5

An overvoltage suppressing apparatus, comprising: a DC power source; a three-phase voltage source inverter having DC power input terminals connected to the DC power source and having three output terminals; three reactors having input terminals connected to respective of the output terminals of the voltage source inverter and taps provided as output terminals for connection to the primary side of a boosting transformer; a clamping circuit including three diodes for clamping the three output terminals of said reactors to a first predetermined potential so that the respective potentials on said output terminals of said reactors do not exceed said first predetermined potential; and three capacitors each having one end connected to one of the output terminals of said reactors and another end coupled to a second predetermined potential, said capacitors and said reactors forming resonant circuits which limit changes in potential between said first and second predetermined potentials of said output terminals to a resonance curve defined by said resonant circuits.

Claim 6

An overvoltage suppressing apparatus according to claim 3, comprising: a diode bridge having AC input terminals connected to respective of said another ends of said capacitors and DC output terminals connected to a second DC power source.

Claim 7

An overvoltage suppressing apparatus according to claim 4, wherein said second DC power source is a constant-voltage DC power source including: a three-phase AC power source; a rectifying circuit for rectifying an output voltage of said three-phase AC power source; and a smoothing reactor and a smoothing capacitor for smoothing a rectified output of said rectifying circuit.

Claim 8

An overvoltage suppressing apparatus according to claim 3, comprising: a transformer having a primary winding and a secondary winding, said primary winding connected to said another ends of said capacitors, and a three-phase diode bridge having AC input terminals connected to said secondary winding.

Claim 9

An overvoltage suppressing apparatus according to claim 3, wherein said clamping circuit includes a three-phase diode bridge having AC input terminals connected to the other ends of said reactors and DC output terminals connected to said DC power source, and wherein said capacitors each have one end connected to the other end of a respective of said reactors and the other end thereof connected to an adjacent AC terminal of a three-phase diode bridge connected to an AC power source.

Claim 10

An overvoltage suppressing apparatus according to claim 3, wherein said clamping circuit includes a three-phase diode bridge having AC input terminals connected to said taps and DC output terminals connected to said DC power source, and wherein said capacitors are three-phase connecting capacitors each having one end connected to the other end of a respective of said reactors, the other ends of said capacitor being Y-connected.

Claim 11

An overvoltage suppressing apparatus according to claim 8, wherein said second DC power source includes: a three-phase AC power source; a rectifying circuit for rectifying an output voltage of said three-phase AC power source; and a smoothing reactor and a smoothing capacitor for smoothing a rectified output of said rectifying circuit, a terminal of said smoothing capacitor being connected to the DC output terminal of said three-phase diode bridge.

Claim 12

An overvoltage suppressing apparatus, comprising: a first DC power source; a three-phase voltage source inverter having DC power input terminals connected to the first DC power source and having three output terminals; three reactors having input terminals connected to respective of the output terminals of the voltage source inverter and output terminals for connection to the primary side of a boosting transformer; a clamping circuit including three diodes for clamping the three output terminals of said reactors to a predetermined potential so that the respective potentials on said output terminals of said reactors do not exceed said predetermined potential; and three capacitors having one end connected to respective of the output terminals of said reactors and another end commonly interconnected to each other, said capacitors and said reactors forming resonant circuits which limit potential changes at the reactor output terminals to a resonance curve defined by said resonant circuits.

Claim 13

An overvoltage suppressing apparatus, comprising: a first DC power source; a three-phase voltage source inverter having DC power input terminals connected to the first DC power source and having three output terminals; three reactors having input terminals connected to respective of the output terminals of the voltage source inverter and output terminals for connection to the primary side of a boosting transformer; a clamping circuit including three diodes for clamping the three output terminals of said reactors to a predetermined potential so that the respective potentials on said output terminals of said reactors do not exceed said predetermined potential; and three capacitors having one end connected to respective of the output terminals of said reactors and another end commonly interconnected to each other, said capacitors and said reactors forming resonant circuits which limit potential changes at the reactor output terminals to a resonance curve defined by said resonant circuits.

Claim 14

An overvoltage suppressing apparatus according to claim 10, wherein said clamping circuit includes a three-phase diode bridge having AC input terminals connected to the other ends of said reactors and DC output terminals connected to a second DC power source at said predetermined potential.

Claim 15

An overvoltage suppressing apparatus according to claim 11, wherein said second DC power source is also used as the DC power source for said voltage source inverter.

Claim 16

An overvoltage suppressing apparatus according to claim 12, wherein the other ends of said capacitors

Claim 17

An overvoltage suppressing apparatus according to claim 11, wherein said second DC power source includes: a three-phase AC power source; a rectifying circit for rectifying an output voltage of said three-phase AC power source; and a smoothing reactor and a smoothing capacitor for smoothing a rectified output of said rectifying circuit, a terminal of said smoothing capacitor being connected to the DC output terminal of said three-phase diode bridge.