Thyristor Variable Resistor as a Power Component

Abstract

If we could realize a power variable resistor of which resistance can be varied at will, we would have many applications of it in the field of control and measurement.
For this purpose, a mechanical variable resistor is not adequate in its response and available power. The thyristor variable resistor to be mentioned here is a power variable resistor in which the equivalent resistance between two terminals is varied by means of controlling thyristor switches. Owing to the use of thyristors, we can expect the variable resistor to have a fast response as compared with mechanical ones.
In this paper, we describe the thyristor variable resistor circuit using choppers and constant resistor element. This circuit can be used in both DC and AC systems. From the circuit analyses, we obtain the equivalent resistance and its practical variable range. Furthermore we give an example of thyristor gate control circuit to get the linear characteristics. Next we give the design criterion of the filter that absorbs the variation of the load current occurred by the switching. Lastly we exhibit the experimental circuit which has the variable range from 10 to 100Ω and the rate current 10A. We obtained satisfactory test results.