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Class F Commutation Figure 48 shows the class F commutation and it is voltage and current waveforms are depicted in Fig. 49. This type of commutation is also known as natural commutation or ac line commutation. This type of commutation…
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Class E commutation Figure 46 shows the class E commutation circuit. In this commutation method, the reverse voltage applied to the current carrying thyristor from an external pulse source. This commutation is also known as external…
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Class D Commutation Figure 44 shows the class D commutation circuit which consists of two thyristors such as main thyristor T1 and auxiliary thyristor TA, inductor L, diode D and a commutation capacitor C. The main thyristor T1 and load…
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Class C Commutation Figure 42 shows the class C commutation circuit which consists of two thyristors such as main thyristor T1 and auxiliary thyristor TA and a commutating capacitor. The load resistance RL is connected in series with…
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Class B Commutation Figure 40 shows the class B commutation circuit which consist of thyristor T1 and L-C circuit. Class B commutation is a self-commutation process by an L-C circuit. The L-C resonating circuit is connected across the…
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Class A commutation or Resonant Commutation Figure 35 shows the Class A commutation circuit where L and C are commutation components and RL is load resistance. For low value of load resistance, RL, L and C are connected in series as…
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Line Commutation and Forced Commutation Circuits Once thyristors operate in the ON state, carrying forward current, they can only be turned OFF by reducing the current flowing through them to zero for sufficient time to allow the removal…
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Snubber Circuit In most power electronic circuits, protection is necessary against the effects of excessive rate of rise of forward voltage (dv/dt) across the devices, which can otherwise cause unintended breakover, leading to a…
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String Efficiency For series or parallel connected SCRs, it should be ensured that each SCR rating is fully utilized and the system operation is satisfactory. Therefore, string efficiency is a term that is used for measuring the degree…
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Parallel Operation of Thyristors The need to connect thyristors in parallel arises when the current or over current to be handled by the apparatus or equipment exceeds the rating of a single thyristor. Thyristors can be connected…
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