Multimeter measurement of thyristor_How to measure the good and bad thyristor
There are two types of SCRs, unidirectional SCRs and bidirectional SCRs, both with three electrodes. Unidirectional SCRs have a cathode (K), anode (A), and control pole (G). Bidirectional thyristor equivalent to two single thyristor reverse parallel. That is, one of the unidirectional silicon anode and the other cathode side by side, its lead end is called T2 pole, one of the unidirectional silicon cathode and the other anode is connected to the lead end is called T2 pole, and the rest is the control pole (G).
1, single, bidirectional thyristor discernment: first any two poles, if the positive and negative measurement of the pointer are not moving (R × 1 block), it may be A, K or G, A pole (on the unidirectional thyristor) may also be T2, T1 or T2, G pole (on the bidirectional thyristor). If one of the measurement instructions for tens to hundreds of ohms, it must be unidirectional thyristor. And the red pen connected to the K pole, the black pen connected to the G pole, the rest is the A pole. If the positive and negative measurement instructions are tens of hundreds of ohms, it must be bidirectional thyristor. Then dial the knob to R × 1 or R × 10 block retest, which must be a slightly larger resistance, a slightly larger red pen connected to the G pole, the black pen connected to the T1 pole, the rest is T2 pole.
2, the difference in performance: the knob will be dialled to R × 1 block, for 1 ~ 6A unidirectional SCR, red pen to K pole, black pen at the same time connected to the G, A pole, in keeping the black pen does not detach from the state of the A pole under the G-pole, the pointer should indicate a few tens of ohms to one hundred ohms, at this time the SCR has been triggered, and the trigger voltage is low (or triggering current is small). Then instantaneously disconnect the A-pole and then connected, the pointer should be returned to ∞ position, it shows that the thyristor is good.
For 1 ~ 6A bidirectional thyristor, red pen connected to the T1 pole, black pen connected to the G, T2 pole at the same time, in order to ensure that the black pen does not detach from the T2 pole under the premise of disconnecting the G pole, the pointer should be indicated as tens of more than one hundred ohms (depending on the size of the current of the thyristor, different manufacturers and different). Then the two pens will be adjusted, repeat the above steps to measure a pointer than the last slightly larger than a dozen to dozens of ohms, indicating that the SCR is good, and the trigger voltage (or current) is small. If you keep connected to the A pole or T2 pole when disconnecting the G pole, the pointer immediately returned to the ∞ position, then the SCR trigger current is too large or damaged. Can be further measured in accordance with Figure 2 method, for unidirectional SCR, close the switch K, the light should be bright, disconnect the K light is still not extinguished, otherwise the SCR is damaged.
For bi-directional SCR, close the switch K, the light should glow, disconnect K, the light should not be extinguished. Then the battery is reversed, repeat the above steps, should be the same result, it is good. Otherwise, the device is damaged.
