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SCR Commutation Question & Answers

November 2, 2022 By WatElectronics

This article lists 50 SCR Commutation MCQs for engineering students. All the SCR Commutation Questions & Answers given below include a hint and a link wherever possible to the relevant topic. This is helpful for users who are preparing for their exams, interviews, or professionals who would like to brush up on the fundamentals of SCR Commutation.

Transistors require voltages at the gate terminal to get turned ON and as the flow of voltage is stopped, it gets turned OFF. But this is not the case in thyristors or SCRs. Turning it ON require Gate voltage but as the voltage flow gets stopped still it will be in the mode of conduction.

To turn it OFF i.e., to bring SCR from its forward mode of conduction to the forward state of blocking requires reducing anode currents below the level of holding currents. The process of turning OFF SCRs is referred to as Commutation.

Commutation is about transferring currents between circuits. Directions of current can be reversed in windings as the commutators present in DC motors. Brush assembly consists of such commutators.

Similarly in SCRs forward or the Anode currents are reduced to zero and it is turned Off. After it is OFF SCR can conduct forward voltages immediately. SCRs contain only OFF and ON states and also it doesn't have any control overload current and voltages.

1). What is SCR commutation?

Hint
2). Turning OFF thyristor indicates that it is in ____________ mode.

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Read More about Turn OFF SCR 
3). SCR in _____________ mode makes the gate to lose control?

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4). External circuit used in SCR turn OFF referred to as ____________?

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5). What should be less than holding currents to turn OFF SCR?

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6). Which voltage is applied around SCR to regain its forward mode of blocking from conduction?

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7). SCRs does not require ___________ to remain in ON state?

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8). Reverse voltages applied around SCR accelerates __________?

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9). How many states does any SCR have?

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10). SCRs does not have control over ____________?

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11). Commutation is ___________ process?

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12). What happens if SCR turns OFF?

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13). Reverse voltage applied in SCR Commutation referred to as __________?

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14) On what basis methods in commutations of SCR classified?

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15). What are the various methods of SCR commutation?

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16). What is turn OFF time of SCR?

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17). What happens at SCRs turn OFF time?

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18). What commutations have commutation voltages as its source of supply?

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19). ___________ occurs in AC circuitry only?

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20). If AC supplied to SCR, what happens at the end of each 'positive half' of the cycle?

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21). In how many categories, forced technique of commutations classified?

Hint
22). Natural Commutation method of SCR also referred to as__________?

Hint
23). Natural Commutation of SCR can be made possible by ____________?

Hint
24). In Natural Commutation, tOFF should be _________ than supply half cycles duration.

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25). What commutations takes place in DC circuitry?

Hint

SCR Commutation MCQ for Quiz

26). What requires the circuit externally to commutate SCR?

Hint
27). Forward current in Forced commutation of SCRs are forcefully made __________?

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28). What does commutating circuitry consists?

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29). What causes the reverse voltages to applied around SCR?

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30). What are self-commutation classes in Forced Commutation?

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31). Class A commutation occurs by __________?

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32). The source for voltage commutation is in _______ for Class A Commutation?

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33). Commutating components in Class A commutation connected in ___________with Load resistance?

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34). ____________ RLC circuit of resonance selected in Self-commutation?

Hint
35). Forward currents flow through SCR makes the capacitor ___________?

Hint

SCR Commutation MCQ for Students

36). What determines the time to switch OFF SCR in Class A commutation?

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37). Resonant Frequency of Class A commutation depends on ________?

Hint
38). Class A method of commutation utilized in ___________?

Hint
39). SCR in Class B commutation has LC circuit connected in __________with Load?

Hint
40). In Class B of commutations, what happens if commutating currents are high than load currents?

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41). ____________ commutation is referred to as Complementary commutation?

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42). ___________ gets connected to load serially in Class C Commutation?

Hint
43). Frequencies below thousand Hertz use ___________ commutation?

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44). SCRs with slower times of turning OFF are referred to as _________?

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45). Externally applied pulse produces reverse voltages around SCR in __________ commutation?

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SCR Commutation MCQ for Interviews

46). What used to switch the capacitor charged in Class D of commutations?

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47). Single-phase inverters use _________ commutation?

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48). Chopper Circuits use _________ Commutation?

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49). Series Inverters use ____________ Commutation?

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50). Inverter and the chopper circuitry use _____________?

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