How to use a multimeter to determine whether a thyristor is good or bad
Thyristor is a high-power semiconductor switching device, whose main function is to achieve precise control of current. The voltage drop during its conduction and turn off processes is relatively small, so it is widely used in the field of power electronics. When using thyristors, there are several methods to measure and judge the quality of thyristors:
1. Observe the appearance
Firstly, one can determine whether the thyristor is damaged by observing its appearance. Under normal circumstances, the surface of the thyristor should have no obvious scratches, cracks, or other phenomena. If damage or burning is found on the surface of the thyristor, it indicates that the thyristor may have been damaged.
2. Check the pins
Secondly, the pins of the thyristor can be checked for looseness, breakage, and other phenomena. Under normal circumstances, the pins of the thyristor should be firmly connected to the circuit board without any corrosion. If loose or broken pins are found, it indicates that the thyristor may have been damaged.
3. Measure resistance
To more accurately determine the quality of thyristors, a multimeter can be used to measure their resistance. Connect the red probe of the multimeter to the gate of the thyristor (A+) and the black probe to the emitter of the thyristor (K). At this point, the multimeter should display a lower resistance value (usually between a few hundred ohms and several thousand ohms). If the resistance value displayed on the multimeter is infinite or very high, it indicates that the thyristor may have been damaged; If the resistance value displayed on the multimeter is low, it indicates that the thyristor is working properly.
4. Test the ability to turn on and off
To further evaluate the quality of thyristors, tests can be conducted on their conduction and turn off capabilities. Connect the thyristor to an appropriate load (such as a light bulb, motor, etc.), and then input a forward current signal. If the thyristor can conduct normally and withstand the current of the load, and can quickly cut off the current when turned off, it indicates that the thyristor is working normally; If the thyristor cannot conduct or cannot turn off normally after conducting, it indicates that the thyristor may have been damaged.
5. Check the drive circuit
In addition to directly inspecting the thyristor itself, it is also necessary to check whether its driving circuit is working properly. If the driving circuit malfunctions, it may cause the thyristor to malfunction. Oscilloscope or other testing instruments can be used to check the signal waveform of the drive circuit to determine if it is normal.
