thyristor


Posted on Feb 7, 2014

A thyristor is like a diode; it can pass electricity in a forward direction but, blocks it in a reverse direction. The difference between a diode and a thyristor is that the thyristor is a three terminal device consisting of an anode, cathode and gate, which will also block current flow in the forward direction until it`s gate is signaled to open


thyristor
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or, to use more technical jargon, the thyristor is fired . Once turned on, the gate signal is removed and the thyristor remains on until the current through it drops to zero, which conveniently happens during each cycle of the main supply. Thyristors are most commonly known as Silicon Controlled Rectifiers (SCRs), Triacs, Thyristor Surge Protective Devices & SIDACs, and Programmable Unijunction Transistor (PUT). Although it can take many forms, they all have certain things in common. Normally-off  switches, a small current pulse into the gate electrode can trigger thyristors on . Once triggered, the component then stays in the conducting state even when the gate on signal is removed. It only returns to the off  (blocking) state if the current falls below a certain minimum or if the direction of the current is reversed. The circuit symbol is shown below. When there is no gate current, the device is in the non-conducting state and will hold off positive and negative bias voltages. The zero gate current characteristic is: Coilgun Thyristors are the device of choice when using a basic capacitor discharge coilgun. The thyristor will hold off the capacitor voltage until it is triggered into the forward conduction zone by the gate current signal. The capacitor then discharges through the thyristor into the coil and the current decays to zero. There is no option for turning off the current once the device is conducting....




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