The most important member of the thyristor family is the three wire thyristor , also known as the silicon controlled rectifier or SCR. This device was developed and given by the name SCR by the General Electric Company in 1958. The name thyrsistor was adopted later by the international Electrotechnical comission. The symbol for a three wire thyristor or SCR is shown below.
As the name suggests the SCR is a controlled rectifier or a diode. Its voltage current characterisctics with the gate lead open is the same as that of a PN PN diode.
Three wire thyrsitor or SCRs are by far the most common devices used in power control circuits. They are widely used for switching or rectification applications and are currently available in ratings ranging from a few amperes upto a maximum of about 3000A.
In summary , an SCR is
As the name suggests the SCR is a controlled rectifier or a diode. Its voltage current characterisctics with the gate lead open is the same as that of a PN PN diode.
Three wire thyrsitor or SCRs are by far the most common devices used in power control circuits. They are widely used for switching or rectification applications and are currently available in ratings ranging from a few amperes upto a maximum of about 3000A.
In summary , an SCR is
- Turns on when a voltage Vd applied to it exceeds Vbo.
- Has a breakover voltage Vbo whose level is controlled by the amount of gate current Ig present in the SCR.
- Turns off when the current Id flowing it drops below Ih.
- Blocks all current flow in the reverse direction until the maximum reverse voltage is exceeded.
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