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Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?
- a)26.23 Ω
- b)50 Ω
- c)16.67 Ω
- d)33.33 Ω
Correct answer is option 'C'. Can you explain this answer?
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Most Upvoted Answer
Three SCRs are connected together to form a series string. The voltage...
Concept:
- Need of series connection of SCR is required when we want to meet the increased voltage requirement by using various SCR’s.
- When the required voltage rating exceeds the SCR voltage rating, a number of SCR’s are required to be connected in series to share the forward and reverse voltage.
- When the load current exceeds the SCR current rating, SCR are connected in parallel to share the load current.
Application:
According to the question:
According to the question:
Given that
SCR 1 voltage = 350 V; current = 6 A
SCR 2 voltage = 300 V; current = 9 A
SCR 3 voltage = 250 V; current = 12 A
Let us take the total current to be ‘I’
Current through resistor R in shunt with SCR 1 is
SCR 1 voltage = 350 V; current = 6 A
SCR 2 voltage = 300 V; current = 9 A
SCR 3 voltage = 250 V; current = 12 A
Let us take the total current to be ‘I’
Current through resistor R in shunt with SCR 1 is
I1 = I – 6
Similarly, current through resistor R is shunt with SCR 2
I2 = I – 9
And, current through resistor R in shunt with SCR 3
I3 = I – 12
Now, the string voltage becomes
Vs = I1R + I2R + I3R
Vs = (I - 6) R + (I - 9) R + (I - 12) R
Vs = (I - 6) R + (I - 6) R – 3 R + (I - 6) R – 6 R …..(1)
Note that
We should consider the extreme case from the calculation of resistance R for voltage equalization in string of SCR.
In extreme case, the voltage drop across SCR 1 (or the one having highest voltage drop) will be maximum forward blocking voltage.
∴ Vmax = 350 = (I - 6) R ----(2)
Put (I - 6) R = 350 in equation (1), we get
Vs = 350 + 350 – 3 R + 350 – 6 R
(350 + 300 + 250) = 1050 – 9 R
900 = 1050 – 9 R
9 R = 1050 – 900
R = 150/9Ω
R = 16.66 Ω
Therefore the value of equalising resistance to be used across each thyrister is 16.66 Ω.
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Community Answer
Three SCRs are connected together to form a series string. The voltage...
B) 21.88
c) 17.54
d) 14.58
To find the value of the equalizing resistance, we need to calculate the voltage drop across each thyristor.
Voltage drop across thyristor 1 = 350V - 300V = 50V
Voltage drop across thyristor 2 = 300V - 250V = 50V
Now, we can calculate the resistance using Ohm's Law:
Resistance = Voltage drop / Current
Resistance 1 = 50V / 6A = 8.33 Ω
Resistance 2 = 50V / 9A = 5.56 Ω
To find the total resistance in the series string, we can add the resistances of each thyristor:
Total resistance = Resistance 1 + Resistance 2 = 8.33 Ω + 5.56 Ω = 13.89 Ω
However, this total resistance needs to be divided equally among the three thyristors. Therefore, the value of the equalizing resistance for each thyristor will be:
Equalizing resistance = Total resistance / Number of thyristors = 13.89 Ω / 3 = 4.63 Ω
Rounding to two decimal places, the value of equalizing resistance to be used across each thyristor is 4.63 Ω, which is closest to option c) 4.63.
c) 17.54
d) 14.58
To find the value of the equalizing resistance, we need to calculate the voltage drop across each thyristor.
Voltage drop across thyristor 1 = 350V - 300V = 50V
Voltage drop across thyristor 2 = 300V - 250V = 50V
Now, we can calculate the resistance using Ohm's Law:
Resistance = Voltage drop / Current
Resistance 1 = 50V / 6A = 8.33 Ω
Resistance 2 = 50V / 9A = 5.56 Ω
To find the total resistance in the series string, we can add the resistances of each thyristor:
Total resistance = Resistance 1 + Resistance 2 = 8.33 Ω + 5.56 Ω = 13.89 Ω
However, this total resistance needs to be divided equally among the three thyristors. Therefore, the value of the equalizing resistance for each thyristor will be:
Equalizing resistance = Total resistance / Number of thyristors = 13.89 Ω / 3 = 4.63 Ω
Rounding to two decimal places, the value of equalizing resistance to be used across each thyristor is 4.63 Ω, which is closest to option c) 4.63.
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Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer?
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Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer?.
Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer? for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Question and answers have been prepared according to the Electrical Engineering (EE) exam syllabus. Information about Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer?.
Solutions for Three SCRs are connected together to form a series string. The voltages across the thyristors are 350V, 300V and 250V respectively. If the currents in the thyristors are 6A, 9A, and 12A respectively, what will be the value of equalising resistance to be used across each thyristor?a)26.23 Ωb)50 Ωc)16.67 Ωd)33.33 ΩCorrect answer is option 'C'. Can you explain this answer? in English & in Hindi are available as part of our courses for Electrical Engineering (EE).
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