Thermal plotter system for thyristor under load - uses proportional amplifiers and first-order delay networks to simulate thermal conditions

摘要

The simulator circuit for plotting the thermal characteristics of a thyristor under load consists of an input network fed with the thyristor load current (IF). The network comprises parallel branches with linear amplifier (1) representing the gate voltage and a squarer (2) in series with a second linear amplifier (3) representing the differential internal resistance of the anode-cathode circuit of the thyristor. The outputs of the two branches are added and fed to the inputs of two parallel, first-order delay networks (4, 5) representing the time responses of the internal and external thermal resistances of the thyristor. The output of the simulator - the temperature difference between junction and ambient is compared with a reference current taken from a resistor in series with the slider of a potentiometer connected across a voltage source. The final output is used to control the thyristor current and/or to drive an indicator and recording instrument.