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Equalising Network Voltage equalisation under these conditions can, however, be achieved by connecting shunt-capacitors as shown in Figure 28. This capacitor removes inequalities in thyristor self-capacitances. Therefore, during turn-off…
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Series Operations of Thyristors If the required voltage rating of the assembly or equipment incorporating thyristors is more than the voltage rating of a single thyristor, then several thyristors have to be united in a series connection.…
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Ratings of SCR All semiconductor devices have definite limits to their capability and exceeding these even for short times will result in failure, loss of control, or irreversible deterioration. All thyristors, therefore, have to be used…
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Overcurrent Protection of SCRs As the thyristors have a restricted overcurrent capacity, special fast-acting fuses and circuit breakers are usually provided for overcurrent protection. As the fault current increases, the fuse opens and…
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Overvoltage Protection of SCRs It is almost always necessary in a power semiconductor equipment to provide a means of limiting transient overvoltages which could otherwise overstress the semiconductor devices. To protect against all…
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Dynamic Characteristics of SCR The static characteristics gives no indication as to the speed at which the SCR is capable of being switched from the forward blocking voltage to the conducting state and vice-versa. However, the transition…
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Two-Transistor Model of SCR (Two Transistor Analogy) The operation of an SCR can also be explained very simply by considering it in terms of two transistors. This is known as the two-transistor analogy of the SCR. The SCR can be…
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Turn-Off Methods of A Thyristor The term commutation basically means the transfer of current from one path to another. In thyristor circuits, this term is used to describe process of transferring current from one thyristor to another. As…
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A thyristor can be switched from a nonconducting state to a conducting state in several ways described as follows. 1.9.1 Forward Voltage Triggering When anode-to-cathode forward voltage is increased with gate circuit open, the reverse…
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An elementary circuit diagram for obtaining static V-I characteristics of a thyristor is shown in Figure 17. Here, the anode and cathode are connected to the main source through a load. The gate and cathode are fed from another source Eg.…
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