- SCR damage discrimination detection
You can use the R×1k or R×100 range of a multimeter to measure the forward and reverse resistance between any two poles. If you find a pair of poles with a low resistance value (100Ω～lkΩ), then the black probe is connected to the control pole, the red probe is connected to the cathode, and the other pole is the anode. Thyristors have three PN junctions, and we can determine their quality by measuring the positive and negative resistance of the PN junctions.
When measuring the resistance between the control electrode (G) and the cathode (C), if both the forward and reverse resistances are zero or infinite, it indicates that the control electrode is short circuited or open circuited; When measuring the resistance between the control electrode (G) and the anode (A), both the forward and reverse resistance readings should be very large; When measuring the resistance between the anode (A) and the cathode (C), both the forward and reverse resistance should be very high.
- Identification and detection of damage to bidirectional thyristors
A bidirectional thyristor has a main electrode 1, a main electrode 2, and a control electrode. If a multimeter is used to measure the resistance between two main electrodes in the R × 1k range, the reading should be approximately infinite, while the positive and negative resistance readings between the control electrode and either main electrode are only a few tens of ohms.
Based on this characteristic, we can easily identify the control electrode of a bidirectional thyristor by measuring the resistance between the electrodes. And when the black probe is connected to the main electrode 1. When the red probe is connected to the control electrode, the forward resistance measured is always smaller than the reverse resistance. Based on this, we can easily identify main electrode 1 and main electrode 2 by measuring the resistance size.
