PURPOSE: To divide and reduce a surge voltage and to make a protecting device compact, by inserting the protecting device comprising a parallel circuit of a resistor and electrostatic capacitors between the secondary output terminal of a testing transformer and a load.
CONSTITUTION: A secondary output terminal 3 of a main body 2 of a testing transformer, which is enclosed in a container 1, is connected to an electric unit 9 in a container 8 through a protecting device 5 in a container 4 and an insulating spacer 7 in a container 6. The device 5 is constituted by a parallel circuit of a resistor element 5a and capacitor elements 5b. When a high voltage is applied from the main body 2 and a surge voltage is generated on a load side, the surge voltage is applied to the terminal through the device 5. The peak value of the voltage is divided by the impedance ratio between the circuit 5 and the main body 2. The divided surge voltage is applied to the main body 2. In this constitution, the resistance value of the element 5a can be made small in comparison with the case where only the resistor is used. The resistance drop due to a load current can be reduced, and the protecting device can be made compact.
OYABU TSUTOMU
KANO TAKAHARU
ASHIDA JIRO
