Zero trigger integrated circuit temperature control circuit 4

It is a furnace temperature automatic control circuit using KJ007 zero-trigger integrated circuit. It has the characteristics of high temperature control accuracy, wide range,
high sensitivity and simple circuit. The power of the electric furnace can reach 4kW (single phase) and 12kW (three phase).
    The temperature sensing element is a thermistor R with negative temperature coefficient. The entire device consists of power supply circuit, temperature control circuit and zero trigger
circuit. A three-terminal fixed integrated voltage regulator Ai is used to provide DC power, a 555 time base integrated circuit Az
is used as the temperature control circuit, and an I(J007 zero-trigger integrated circuit A3 is used as the trigger control circuit of the bidirectional thyristor V.
    If used in a three-phase circuit As shown in the dotted line and the figure inside the dotted box, as long as three sets of identical zero- trigger circuits are used
. The maximum capacity of each phase bidirectional thyristor is 50A. If this value is exceeded, the output power of KJ007 must be expanded.