3T intermediate frequency furnace requirements for trigger circuit
The function of the 3T intermediate frequency furnace trigger circuit is to generate the required gate trigger pulse to ensure that the 3T intermediate frequency furnace is turned from blocking to conducting at the required time. Broadly speaking, the 3T intermediate frequency furnace trigger circuit often also includes a phase control circuit that controls the departure time.
The 3T intermediate frequency furnace trigger circuit should meet the following requirements:
The width of the trigger pulse should ensure that the 3T intermediate frequency furnace can be turned on. For the inductive and back EMF load converters, wide frequency pulse or pulse train trigger should be used. For the start of the converter, the trigger pulse of the double star line with the balanced reactor circuit should be For wider than 30o, the three-phase fully controlled bridge circuit should be wider than 60o or double narrow pulses separated by 60o.
The trigger pulse should have sufficient amplitude. For cold outdoor conditions, the amplitude of the pulse current should be increased to 3-5 times of the maximum trigger current of the device, and the steepness of the pulse front edge should also be increased, generally reaching 1-2 A/μs.
The trigger pulse provided shall not exceed the voltage, current and power rating of the 3T IF furnace gate and be within the reliable triggering region of the gate volt-ampere characteristics.
It should have good anti-interference performance, temperature stability and electrical isolation from the main circuit.
The following picture shows the common 3T intermediate frequency furnace trigger circuit.

It consists of a pulse amplifying link composed of V1 and V2 and a pulse number output link composed of a pulse transformer TM and an auxiliary circuit. When V1 and V2 are turned on, a trigger pulse is outputted between the gate and the cathode of the 3T intermediate frequency furnace through the pulse transformer. VD1 and R3 are set for the pulse transformer TM to release its stored energy when V1 and V2 are turned on and off.