How to use a multimeter and megohmmeter to check the quality of reverse conducting thyristors

The reverse conducting thyristor test content is mainly divided into three items:

1. Check the reverse conductivity

Select the multimeter R×1, connect the black test lead to the K pole and the red test lead to the A pole, the resistance value should be 5~10Ω. If the resistance value is zero, it proves that the internal diode is short-circuited; if the resistance is infinite, it means that the diode is open-circuited.

2. Measure the forward DC breakover voltage V(BO)

Connect the circuit, then shake the megohmmeter at the rated speed to make the RCT break down in the forward direction, and read the V(BO) value from the DC voltmeter.

3. Check the trigger capability

Example: Use a 500-type multimeter and a ZC25-3 megohmmeter to measure a S3900MF reverse-conducting thyristor. Select the R×1k, R×100, R×10 and R×1 ranges to measure the reverse resistance between the AK poles, and use the voltage reading method to calculate the reverse conduction voltage VTR of the internal diode (actually the forward voltage VF of the diode). Then use the megohmmeter and the 500VDC range of the multimeter to measure the V(BO) value. All data are organized into a table. This proves that the quality of the RCT being tested is good.