How to detect thyristors! Different types of thyristor detection methods

The basic detection method of thyristor?
1. Identify the anode, cathode and control electrode of the unidirectional thyristor?
Unplug the unidirectional thyristor of the circuit board, the anode, cathode and control pole 3 pins generally have no special labels. The identification of each pin is mainly carried out by detecting the positive and negative resistance values between the pins. The resistance between the pins of the thyristor is relatively large. When a small resistance is detected, the black test lead is connected to the control electrode (G), the red test lead is connected to the cathode (K), and the other pin is Anode (A). ?
2. Judge the quality of the unidirectional thyristor?
Unplug the one-way thyristor of the circuit board, the anode (A), cathode (K) and control electrode (G) are clearly marked; normal one-way thyristor, between the two pins of the anode (A) and cathode (K) Positive and reverse resistance, the resistance of the positive and negative resistance between the anode (A) and the control electrode (G) should be large, the cathode (K) and the control electrode (G) two pins The forward resistance should be much smaller than the reverse resistance. And the greater the forward resistance between the anode (A) and cathode (K) pins, the better the positive blocking characteristics of the unidirectional thyristor anode; the greater the reverse resistance, the better the reverse resistance of the unidirectional thyristor anode The better the breaking characteristics. ?
3. Judge the quality of the bidirectional thyristor?
Remove the bidirectional thyristor of the circuit board, the electrode (T1), the second electrode (T2), and the control electrode (G) are clear. To judge the quality of the bidirectional thyristor, it mainly depends on the resistance between the second electrode (T2) and the electrode (T1) before the short circuit is close to infinity, the second electrode (T2) and the control electrode (G) pin are short-circuited, and the thyristor is triggered after the short circuit. When it is turned on, the resistance between the second electrode (T2) and the electrode (T1) becomes smaller and has a fixed value. It can be concluded that the bidirectional thyristor has a bidirectional triggering capability, and the performance is basically good. ?
4. What is the replacement principle of thyristor?
There are many varieties of thyristors, and different electronic devices and different electronic circuits use different types of thyristors. When selecting and replacing the thyristor, the main consideration should be its rated peak voltage, rated current, forward voltage drop, gate trigger current and trigger voltage, switching speed and other parameters. The rated peak voltage and rated current should be higher than the working circuit. The voltage and working current are 1.5~2 times, and the thyristor of the same type, characteristics and shape should be used for replacement.
Ordinary thyristors are generally used for AC and DC voltage control, controlled rectification, AC voltage regulation, inverter power supply, switching power supply protection and other circuits.
Bidirectional thyristors are generally used in circuits such as AC switches, AC voltage regulators, AC motors linear speed adjustment, lamp linear dimming, solid state relays, and solid state contactors.
Reverse conducting thyristors are generally used in circuits such as induction cookers, electronic ballasts, ultrasonic circuits, superconducting magnetic energy storage systems, and switching power supplies.
Light-controlled thyristors are generally used in photoelectricity combiners, photodetectors, light alarms, light counters, photoelectric logic circuits and automatic production line operation monitoring circuits.
BTC transistors are generally used in sawtooth generators, long time delays, overvoltage protectors, and high-power transistor trigger circuits.
Gate-off thyristors are generally used for AC motor variable frequency speed regulation, choppers, inverter power supplies and various electronic switching circuits.
How to detect thyristors! Different types of thyristor detection methods
How to detect thyristor
The thyristor can be detected by a multimeter electric block. The detection methods of different types of thyristors are introduced below.
(1) Detecting unidirectional thyristor
First put the multimeter in the "RX10Ω" block, and the black test lead (the positive electrode of the battery in the meter is connected to the control electrode G, and the red test lead is connected to the cathode K, as shown in Figure 4-57. At this time, the forward resistance of the PN junction is measured. It has a smaller resistance value. After adjusting the two test leads, the reverse resistance should be significantly larger than the forward resistance.
The black test lead is still connected to the control electrode G, and the red test lead is connected to the anode A. The resistance should be infinite, as shown in Figure 4-58. After measuring with two test leads, the resistance value should still be infinite. This is because two PN junctions are connected in reverse series between G and A, and the forward and reverse resistances are both infinite under normal circumstances.

Then check the continuity characteristics, put the multimeter in the "RX1Ω" block, connect the black test lead to anode A, and the red test lead to cathode K. The needle indicator should be infinite. Use a metal object such as a screwdriver to short-circuit the control electrode G and anode A (it will be disconnected after the short connection), and the needle should be deflected to the right and kept at more than ten ohms, as shown in Figure 4-59. Otherwise, it means that the product brake tube has been damaged.

(2) Detection of bidirectional thyristor
When testing, the multimeter is placed in the "RX1Ω" block, and the forward and reverse resistances between the control electrode G and the main electrode T1 are measured with two test leads. Both should be smaller resistance values, as shown in Figure 4-60. Use two meter pens to measure the forward and reverse resistance between the control electrode G and the main electrode T2. Both should be infinite, as shown in Figure 4-61.


When detects the conduction characteristics of the bidirectional thyristor, the multimeter is still placed in the “RX1Ω” block, the black test lead is connected to the main electrode T1, the red test lead is connected to the main electrode T2, and the needle indication should be infinite. Short-circuit the control electrode G and the main electrode T2, the needle should be deflected to the right and kept at more than ten ohms, as shown in Figure 4-62. If it contains, it means that the bidirectional thyristor has been damaged.
(3) Detection can turn off the thyristor
When testing, put the multimeter in the "RXlΩ" block, connect the black test lead to anode A, and the red test lead to cathode K. The needle indication should be infinite resistance.
A 1.5v battery is used as the control voltage, and a current limiting resistor of about 100Ω is connected in series with the negative electrode of the battery to the cathode K of the thyristor that can be turned off. After touching the control electrode G with the positive electrode of the battery, the meter needle of the multimeter should be turned to the right to indicate that the thyristor is turned on, as shown in Figure 4-63.

Then change the battery polarity, change the positive electrode of the battery in series with a current limiting resistor of about 100Ω connected to the limiter K of the thyristor that can turn off the thyristor. After touching the control electrode G with the negative electrode of the battery, the needle of the multimeter should return to the left The resistance is infinite, indicating that the thyristor has been turned off. Otherwise, it means that the turn-off thyristor is damaged. As shown in Figure 4-64.