The international name of SCR (SCR) is Thyyistoy, or Chinese referred to as thyristor. It can work under the condition of high voltage and high current. It has the advantages of high pressure, high capacity, small volume and so on. It is a high-power switch type semiconductor device. It is widely used in electric power and electronic circuits.
1. characteristics of silicon controlled.
The SCR is divided into unidirectional silicon controlled silicon and bidirectional thyristor. One way SCR has three lead pins: anode A, cathode K and control pole G. The bidirectional silicon controlled rectifier has the first anode A1 (T1), the second anode A2 (T2), and the control pole G three lead feet.
Only when the positive voltage is added between the unidirectional SCR anode A and the cathode K, and the required positive trigger voltage between the polar G and the cathode can be triggered. At this time, A and K showed a low resistance conduction state, and the pressure drop between anode A and cathode K was about 1V. After unidirectional silicon control, the controller G continues to be in a low resistance conduction state even if the positive voltage is still maintained between the anode A and the cathode K, even if the trigger voltage is lost. Only when the anode A voltage is dismantled or the voltage polarity between the anode A and the cathode K changes (zero exchange), the unidirectional thyristor is converted from the low resistance conduction state to the high stop state. Once the unidirectional silicon controlled silicon is cut off, even the positive voltage is added between the anode A and the cathode K, the positive triggering voltage between the control pole G and the cathode K is still necessary. The conduction and cut-off state of the one way thyristor is equivalent to the closing and disconnecting state of the switch, and it can be used as a contactless switch.
Between the bidirectional thyristor first anode A1 and the second anode A2, no matter the polarity of the voltage is positive or reverse, as long as the trigger voltage between the control pole G and the first anode A1 is different from the positive and negative polarity, it can trigger a low resistance state. At this time, the pressure drop between A1 and A2 is about 1V. Once the bidirectional thyristor is switched on, even if the trigger voltage is lost, the conduction state can also be maintained. Only when the current of the first anode A1 and the second anode A2 decreases, the bidirectional thyristor is truncated when the voltage polarity changes between the maintenance current or the A1 and A2, and the voltage polarity is changed without the trigger voltage.
2. unidirectional SCR detection.
The multimeter selects the resistance R*1 Omega block, and uses the red and black two points to measure the positive and reverse resistance of any two pins until the number of a pair of pins which read as dozens of ohms. At this time the black pen is pin for the control pole G, the pin of the red pen is the cathode K, and the other is the anode A. At this time, the black pen is connected to the anode A which has been determined, and the red pen is still connected to the cathode K. At this time, the multimeter pointer should not be moved. With the short line instantaneous short anode A and the control pole G, the resistance indicator of the multimeter should be deflected to the right, and the resistance reading is about 10 ohms. If the anode A is connected with the black pen, when the cathode K is connected with the red pen, the multimeter pointer deflects, indicating that the one way thyristor has been damaged.
3. detection of bidirectional thyristor.
Using the multimeter resistance R*1 ohm block, the positive and negative resistances between any two pins are measured by the red and black two pens respectively, and the result shows that the two sets of readings are infinite. If a group is tens of ohms, the two pins of the red and black tables are the first anode A1 and the control pole G, and the other empty anode is the second anode A2.  When the A1 and G are determined, the positive and reverse resistance of the A1 and G poles is carefully measured. The black pen with relatively small readings is the first anode A1, and the pin of the red pen is controlled to G. The black pen is connected to the determined second anode A2 and the red pen is connected to the first anode A1. At this time, the pointer of the multimeter should not be deflected, and the resistance value is infinite. With short wiring, the A2 and G will be momentarily short, and the positive pole voltage will be added to the G pole. The resistance between A2 and A1 will be about 10 ohms. Then the short wiring between A2 and G will be disconnected, and the reading of multimeter should be maintained at about 10 ohms. Exchange the red and black watch wiring, the red pen is connected to the second anode A2, the black pen is connected to the first anode A1. Similarly, the multimeter pointer should not deflect, and the resistance will be infinite. With short wiring, the A2 and G poles will be connected again for a short time, giving the G pole a negative trigger voltage, and the resistance between A1 and A2 will be about 10 ohms. Then disconnect the A2 and G poles, and the reading of the multimeter should remain unchanged at about 10 ohms. According to the above rule, the bidirectional thyristor is not damaged and the three pin polarity is judged correctly.
When detecting large power thyristors, a 1.5V dry battery will be connected in a multimeter black pen to raise the trigger voltage.
Pin discrimination of thyristor (thyristor)
The foot of the sluice pipe can be judged by the following method: first use the multimeter R*1K to measure the resistance between the three feet, and the small two feet are the control pole and the cathode, the remaining one is the anode. Then put the multimeter on the R*10K gear, pinch the anode and the other foot with the finger, and do not let the two feet contact, the black pen holds the anode, the red pen holds the remaining foot, such as the needle to the right, indicating that the red pen is connected to the cathode, and does not swing for the control pole.