How to detect thyristor with the help of a multimeter
The thyristor is divided into one-way thyristor and two-way thyristor, both of which are three electrodes. The one-way thyristor has a cathode (K), an anode (A), and a control electrode (G). A bidirectional thyristor is equivalent to two single-phase thyristors in reverse parallel connection. That is, one of the one-way silicon anodes is connected to the other cathode, and its leading end is called T2 pole, one of the one-way silicon cathodes is connected to the other anode, and its leading end is called T2 pole, and the rest is the control pole. pole (G).
1. Judgment of single and two-way thyristors: first measure two poles, if the forward and reverse measurement pointers are not moving (R×1 block), it may be A, K or G, A poles (for one-way thyristors) ) may also be T2, T1 or T2, G pole (for triac). If one of the measurements indicates tens to hundreds of ohms, it must be a one-way thyristor. And the red pen is connected to the K pole, the black pen is connected to the G pole, and the rest is the A pole. If the forward and reverse test instructions are tens to hundreds of ohms, it must be a triac. Then turn the knob to R×1 or R×10 for re-testing. One of the resistance values must be slightly larger, then the slightly larger red pen is connected to the G pole, the black pen is connected to the T1 pole, and the rest are T2 poles. .
2. The difference in performance: turn the knob to R×1 gear, for 1~6A one-way thyristor, the red pen is connected to the K pole, the black pen is connected to the G and A poles at the same time, and the black pen is not separated from the A pole state. Disconnect the G pole at the bottom, the pointer should indicate tens of ohms to one hundred ohms, at this time the thyristor has been triggered, and the trigger voltage is low (or the trigger current is small). Then momentarily disconnect the A pole and then turn it on again, the pointer should return to the ∞ position, indicating that the thyristor is good.
For 1~6A triac, the red pen is connected to the T1 pole, the black pen is connected to the G and T2 poles at the same time, and the G pole is disconnected under the premise that the black pen does not leave the T2 pole, and the pointer should indicate tens to more than one hundred. Europe (depending on the size of the thyristor current and different manufacturers). Then switch the two strokes and repeat the above steps to measure once, and the pointer indication is slightly larger than the last time by a dozen to several tens of ohms, indicating that the thyristor is good and the trigger voltage (or current) is small.
If the G pole is disconnected when the A pole or T2 pole is kept connected, and the pointer returns to the ∞ position immediately, it means that the trigger current of the thyristor is too large or damaged. It can be further measured according to the method in Figure 2. For the one-way thyristor, close the switch K, the light should be on, and the light will continue to go out when K is disconnected, otherwise the thyristor is damaged.
For the triac, close the switch K, the light should be on, open K, the light should be off continuously. Then reverse the battery and repeat the above steps, all should be the same result, it is good. Otherwise, the device is damaged.
