| 摘要 |
PROBLEM TO BE SOLVED: To control an input current in a sine wave form, pass a current to a heating coil from an alternating current through the minimum number of semiconductor elements, and do without storage of direct current by obtaining high-frequency alternating current directly from the commercial power source. SOLUTION: A series circuit of diodes D<SB>1</SB>, D<SB>2</SB>and a first and second switching arm series circuits consisting of switching elements S<SB>1</SB>to S<SB>4</SB>and diodes D<SB>3</SB>to D<SB>6</SB>are connected in parallel with each other to make up a first bridge circuit B<SB>1</SB>. Likewise, a bridge circuit B<SB>2</SB>is made up by D<SB>7</SB>to D<SB>12</SB>and S<SB>5</SB>to S<SB>8</SB>. Both inner connection points of the first and the third switching arm series circuit are connected together and both inner connection points of the second and the fourth switching arm series circuits are connected together, and a series circuit of a heating coil 30 and a capacitor C<SB>1</SB>is connected between the inner connection points. An R-phase terminal and a T-phase terminal of a three-phase alternating current power source are connected with the inner connection points of the first and the second diode series circuits and an S-phase terminal is connected with one end of the heating coil. COPYRIGHT: (C)2003,JPO
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