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Q54ModerateRectifiers & Converters

AC source of 110 Vrms, 60 Hz supplies an ideal single-phase phase-controlled half-wave rectifier that charges a battery. Assume the battery is modelled using a voltage source of 100 V with a series resistance of 2Ω Choose the correct option. Statement-1: Minimum value of control firing angle is α = 40° (approx.) Statement-2: For firing angle, α = 60°, the battery current start falling from its peak value after 30° which is measured from the angle at which current starts rising.

Answer & step-by-step solution
Correct answer: A. Both statements are TRUE
Quick explanation

For a controlled half-wave battery charger, current can flow only after the source instantaneous voltage exceeds the battery emf and the SCR is fired. The conduction interval is bounded by the firing instant and the point where source voltage again falls to the battery voltage; evaluating the average current with the given source and load data gives the value in option A.

During conduction: i(θ)=[Vm sinθ−E]/R; Vm=√2 Vrms

Concept and Reasoning

For a controlled half-wave battery charger, current can flow only after the source instantaneous voltage exceeds the battery emf and the SCR is fired. The conduction interval is bounded by the firing instant and the point where source voltage again falls to the battery voltage; evaluating the average current with the given source and load data gives the value in option A.

Calculation / Key Relation

During conduction: i(θ)=[Vm sinθ−E]/R

Vm=√2 Vrms

Exam Takeaway

For a battery load, conduction requires source voltage > battery emf as well as SCR triggering.

Common Mistake

Do not use the resistive-load half-wave average formula without accounting for battery emf.

Quick Trick

For a battery load, conduction requires source voltage > battery emf as well as SCR triggering.

Solution diagram – AC source of 110 Vrms, 60 Hz supplies an ideal single-phase phase-controlled…
Exam tipFor a battery load, conduction requires source voltage > battery emf as well as SCR triggering.
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