PURPOSE: To extend the detection range of a DC control input, by providing a variable bias current supplying means where a bias current is reduced for application of the DC control input in the positive direction and is increased for application of the DC control input in the negative direction.
CONSTITUTION: When a DC control current ic is flowed in the direction of a solid arrow and this direction is the positive direction, an output voltage eo has polarities of + and -. In this case, the output of an amplifier 17 tries to be positive because the positive output voltage eo is inputted to the amplifier 17, but the output of the amplifier 17 becomes zero because of the negative feedback due to a diode 18. Meanwhile, when the DC control current Ic is flowed in the negative direction, the output voltage eo of a magnetic amplifier 16 has polarities (+) and (-), and the amplifier 17 generates a negative output proportional to the negative output voltage eo. Thus, since a bias ampereturn Nbib of the magnetic amplifier 16 is increased according as the output voltage eo is increased in the negative direction, this transformer is operated similarly to a unipolar (negative) momentary current detector even if the DC control input ic is negative.
KIMURA AKIRA
NAKAMURA KIYOSHI
KUROTAKI YOSHIMI
