GATE Electrical Engineering (EE) 2020 Solved Paper

Question : 32 of 65

Marks: +1, -0

Thyristor

T_{1}

is triggered at an angle

a

(in degree) and

T_{2}

at angle of

180^{∘}+a

, in each cycle of sinusoidal input voltage. Assume both thyristor to be ideal. To control the load power over the range of 0 to

2 {kW}

, the minimum range of variation in

{a}

is:

Solution:

Load Impedance

Z=10∠-60^{∘}=10 \cos 60-j 10 \sin 60^{∘}

=(5-j 8.66) Ω

Load is capacitive.
Maximum load power

=2 {kW}=2000

watts.
Power consumed by load

P=I^{2} R

2000=I^{2} × R

{I}=20

aptitude
Output R.M.S. Voltage

{V}= {IZ}=20 × 10=200

volt.
Maximum R.M.S output voltage

=200

volt.
Since load is capacitive, current would lead the voltage.

Minimum range of variation in

{L}

is ( 0 to

120^{∘}

)
Note:- After

120^{∘}

, current would change direction.

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