| 摘要 |
PROBLEM TO BE SOLVED: To detect the grounding failure of a neon transformer without using a tertiary winding. SOLUTION: The neutral point C of secondary windings 16 and 17 is connected to a ground terminal 18 via a voltage detecting means 41. A resistance element 44 is connected in parallel to the voltage detecting means 41. The voltage detecting means 41 is, for instance, a series circuit consisting of a Zener diode 42 and the light emitting device 43L of a photocoupler. If the secondary side is grounded, the potential of the grounding point is a reference potential and the potential of the neutral point C is elevated, a current is applied to the Zener diode 42 and the light emitting device 43L, a photodetector 43P is turned on, a relay 34 is made to operate, a switch 13 is turned from NC to NO and the power supply is cut off.
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