| 摘要 |
PROBLEM TO BE SOLVED: To perform the make and break of AC power by an AC switch in optional timing and mitigate power loss and also to avoid the breakdown of a switching element when an excessive current has flown. SOLUTION: The AC switch 3 is constituted such that the first switch 4 using a thyristor as a switch element and the second switch 5 using a MOSFET are connected in parallel, and usually it supplies a load 11 with AC power via the second switch 5. Hereby, it can break power at an optional point of time, and power loss is suppressed, too. When an excessive current flows by short circuit or the like on load side, a controller 8 detects it immediately by the current detected value from a current transformer 6, and immediately switches on the first switch 4 and switches off the second switch 5. A thyristor withstands an excessive current since the maximum rated current is larger than that of the MOSFET, so in case that an excessive current continues, a fuse 2 blows off to break the current before the thyristor breaks down. COPYRIGHT: (C)2006,JPO&NCIPI
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