Power converting apparatus and method using a multiple three-phase PWM cycloconverter system

A power converting apparatus of a multiple three-phase pulse width modulation cycloconverter system for driving a high voltage AC motor at a variable speed, characterized in that

• said power converting apparatus comprises m (1.ltoreq.m.ltoreq.n) three-phase transformers each having a single set of primary windings and 3.times.j (j=n/m) sets of secondary windings, 3.times.n three-phase reactors individually connected to the secondary windings, and 3.times.n three-phase/single-phase pulse width modulation cycloconverters individually connected to said three-phase reactors, where n is a positive whole number, that
• said primary windings of said three-phase transformer are connected to an external AC power supply while said 3.times.n secondary windings are arranged in three units, each one unit with n sets of secondary windings, and the electric angles between n set of said each secondary windings of said n sets in same unit are different by (where 1.ltoreq.k.ltoreq.n) in phase from each other and the said secondary windings in said three units which have electric angles of the same phase form n groups, said secondary windings, said three-phase reactors and said three-phase/single-phase pulse width modulation cycloconverters connected in series, that
• each of said three-phase/single-phase pulse width modulation cycloconverters includes six pulse width modulation controlled bidirectional semiconductor switches capable of flowing current in the opposite directions therethrough and allowing self switching on and self switching off, three filter capacitors, three-phase AC terminals connected to corresponding ones of said three-phase reactors, and single-phase AC terminals connected to the outside, and said six bidirectional semiconductor switches are connected in a three-phase bridge circuit to said three-phase AC terminals and said single-phase AC terminals while said filter capacitors are connected in delta or star connection to said three-phase AC terminals, that
• the bidirectional semiconductor switches control so that voltages of AC outputs to be outputted to the single-phase AC terminals of said three-phase/single-phase pulse width modulation cycloconverters may have a same phase in each of said units but electric phase angles of fundamental voltage waveform may be different by 120 degrees from each other between said three units, and that
• the single-phase AC terminals of the three-phase/single-phase pulse width modulation cycloconverters in same ones of said units are connected in series and corresponding ones of the single-phase AC terminals at the opposite ends of the series connections are connected in star connection between said three units while the other three terminals are connected to three input terminals of the external high voltage AC motor which is an object of driving.

A power converting method of a multiple three-phase pulse width modulation cycloconverter system for driving a high voltage AC motor at a variable speed, characterized in that,

• using a power converting apparatus of a multiple three-phase pulse width modulation cycloconverter system wherein, said power converting apparatus comprises a single three-phase transformer having a single set of primary windings and 3.times.n sets of secondary windings, 3.times.n three-phase reactors individually connected to said secondary windings, and 3.times.n three-phase/single-phase pulse width modulation cycloconverters individually connected to said three-phase reactors, where n is a positive whole number, that
• said primary windings of said three-phase transformer are connected to an external AC power supply while said 3.times.n secondary windings are arranged in three units, each one unit with n sets of secondary windings, and the electric angles between n set of said each secondary windings of said n sets in same unit are different by 60.degree.-k (where 1.ltoreq.k.ltoreq.n) in phase from each other and the said secondary windings in said three units which have electric angles of the same phase form n groups, said secondary windings, said three-phase reactors and said three-phase/single-phase pulse width modulation cycloconverters connected in series, that
• each of said three-phase/single-phase pulse width modulation cycloconverters includes six pulse width modulation controlled bidirectional semiconductor switches capable of flowing current in the opposite directions therethrough and allowing self switching on and self switching off, three filter capacitors, three-phase AC terminals connected to corresponding ones of said three-phase reactors, and single-phase AC terminals connected to the outside, and said six bidirectional semiconductor switches are connected in a three-phase bridge circuit to said three-phase AC terminals and said single-phase AC terminals while said filter capacitors are connected in delta or star connection to said three-phase AC terminals, that
• the bidirectional semiconductor switches control so that voltages of AC outputs to be outputted to the single-phase AC terminals of said three-phase/single-phase pulse width modulation cycloconverters may have a same phase in each of said units but electric phase angles of fundamental voltage waveform may be different by 120 degrees from each other among said three units, and that
• the single-phase AC terminals of the three-phase/single-phase pulse width modulation cycloconverters in same ones of said units are connected in series and corresponding ones of the single-phase AC terminals at the opposite ends of the series connections are connected in star connection between said three units while the other three terminals are connected to three input terminals of the external high voltage AC motor which is an object of driving;
• said bidirectional semiconductor switches are controlled by a pulse width modulation system so that voltages of AC outputs to be outputted to the single-phase AC terminals of said three-phase/single-phase pulse width modulation cycloconverters may have a same phase in each of said units but electric phase angles of fundamental voltage waveform may be different by 120 degrees from each other among said three units to drive said high voltage AC motor at a variable speed.

A power converting method of a multiple three-phase pulse width modulation cycloconverter system for driving a high voltage AC motor at a variable speed, characterized in that,

• using a power converting apparatus of a multiple three-phase width modulation cycloconverter system wherein, said power converting apparatus comprises m (1.ltoreq.m.ltoreq.n) three-phase transformers each having a single set of primary windings and 3.times.j (j=n/m) sets of secondary windings, 3.times.n three-phase reactors individually connected to the secondary windings, and 3.times.n three-phase/single-phase pulse width modulation cycloconverters individually connected to said three-phase reactors, where n is a positive whole number, that
• said primary windings of said three-phase transformer are connected to an external AC power supply while said 3.times.n secondary windings are arranged in three units, each one unit with n sets of secondary windings, and the electric angles between n set of said each secondary windings of said n sets in same unit are different by 60.degree..div.k (where 1.ltoreq.k.ltoreq.n) in phase from each other and the said secondary windings in said three units which have electric angles of the same phase form n groups, said secondary windings, said three-phase reactors and said three-phase/single-phase pulse width modulation cycloconverters connected in series, that
• each of said three-phase/single-phase pulse width modulation cycloconverters includes six pulse width modulation controlled bidirectional semiconductor switches capable of flowing current in the opposite directions therethrough and allowing self switching on and self switching off, three filter capacitors, three-phase AC terminals connected to corresponding ones of said three-phase reactors, and single-phase AC terminals connected to the outside, and said six bidirectional semiconductor switches are connected in a three-phase bridge circuit to said three-phase AC terminals and said single-phase AC terminals while said filter capacitors are connected in delta or star connection to said three-phase AC terminals, that
• the bidirectional semiconductor switches control so that voltages of AC outputs to be outputted to the single-phase AC terminals of said three-phase/single-phase pulse width modulation cycloconverters may have a same phase in each of said units but electric phase angles of fundamental voltage waveform may be different by 120 degrees from each other between said three units, and that
• the single-phase AC terminals of the three-phase/single-phase pulse width modulation cycloconverters in same ones of said units are connected in series and corresponding ones of the single-phase AC terminals at the opposite ends of the series connections are connected in star connection between said three units while the other three terminals are connected to three input terminals of the external high voltage AC motor which is an object of driving;
• said bidirectional semiconductor switches are controlled by a pulse width modulation system so that voltages of AC outputs to be outputted to the single-phase AC terminals of said three-phase/single-phase pulse width modulation cycloconverters may have a same phase in each of said units but electric phase angles of fundamental voltage waveform may be different by 120 degrees from each other among said three units to drive said high voltage AC motor at a variable speed.