Silicon controlled rectifier with parametric phase shifter

Abstract

The object of this paper is to present a new magnetic ignition device for the silicon controlled rectifier (SCR), called a parametric phase shifter, in which the theoretical range of the firing angle is 360 degrees. In this device, a magnetic frequency subdivider, called a parametron, is used as the supply for the conventional saturable reactor connected to the gate circuit of the SCR. The ac source for the SCR and for the parametron is common or selected to have the same frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</tex> . The supply frequency of the saturable reactor becomes one half ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2 f</tex> ) of the source frequency by the frequency subdividing action of parametron. Thus, the firing angle range of the SCR can be extended to twice the value as that reached by the ordinary ignition circuit with the saturable reactor only. From the experimental results, its range is measured to about 300 degrees. The starting angle of the ignition in this device can be controlled by changing the supply voltage, the loss component of the oscillating circuit, and the constant part of the inductance of the parametron. If this device is used as an SCR amplifier, the characteristics, such as the gain, the linearity, and the maximum output, are improved considerably. As the firing angle can be extended to the inverter zone of the SCR, this combined device can be used as a regenerative braking of dc motor.