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A single-phase SCR based ac regulator is feeding power to a load consisting of 5 Ω resistance and 16 mH inductance. The input supply is 230 V, 50 Hz ac. The maximum firing angle at which the voltage across the device becomes zero all throughout and the rms value of current through SCR, under this operating condition, are
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- 30° and 46 A
- 30° and 23 A
- 45° and 23 A
- 45° and 32 A
Correct Option: C
Vs = 230V, 50Hz
R = 5Ω, L = 16mH
The maximum firing angle at which the volt across device becomes zero is the angle at which device trigger i.e. minimum firing angle to converter.
| α = φ = tan-1 |  |  | = tan-1 | | | |||
| R | R |
| α = φ = tan-1 | | | = 45.1° | |
| 5 |
The current flowing SCR is max at their angle ie. when α = φ, γ = π
| ITrms = | = | |||
| 2z | 2 × √5² + 5.042 |
∴ ITrms = 22.9 ≈ 23 A
