| 摘要 |
A first power source circuit (8), a second power source circuit (6) and a power source circuit (9) are connected to a power supply unit (5). The first power source circuit includes a direct current power source (8A) and a switching element (8B). The power source circuit (8) does not substantially include a resistor and has a relatively low inductance value and a low impedance value properties. The power source circuit (6) includes a direct current power source (6A), a switching element (6B) and a current limiting resistor (6C). The power source circuits (6, 8, 9) use a cable (11) as a common wiring and are connected to a gap. The power source circuit (8), the conductor (11), a coupling transformer (13) and the gap constitute a high frequency alternate current circuit. At this time switches (6F, 6G, 9F, 9G) provided in the power source circuits (6, 9) are opened so as to completely separate the power source circuits (6, 9) from the high frequency alternate circuit. These switches (6G, 6F, 9F, 9G) are used to completely separate the power source circuit (6) from the power source circuit (8) or connect them for complete conduction, and therefore it is desirable that they comprise butt joint type switching devices. In addition, at this time, it is desirable to use a detecting device (30) having a photocoupler (35) and suited to high frequency alternate current as a means for detecting the voltage of the gap.
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