Q16. a) Fig shows a simple voltage regulator circuit. The unregulated supply Vs can vary between 21 V and 24 V and the minimum diode current for stable operation is 7 mA.
Calculate EACH of the following for protection of the diode and to stable load voltage:
(i) the minimum value of Rs (3)
(if) the minimum power rating of Rs (2)
(iii) the minimum value of RL (3)
b) Fig shows a simplified equivalent circuit for a single-phase transformer ignoring the no-load current.
The winding resistances are assumed to be negligible, and the reactance of the secondary has been referred to the primary to give a value equivalent to the reactance effects of both windings.
The transformer has a turns ratio of 5:1 and delivers 105∠-30° A at 86 V.
(i) Sketch a labelled phasor diagram, to show all voltages, currents and angles. (4)
(ii) Calculate EACH of the following:
→ The supply voltage V1
→ The voltage regulation. (8)
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