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Q1. A 9 V power supply delivers 2 A to a resistive load. The a.c. supply is 230 V, 50 Hz and a bridge rectifier is used in conjunction with a 0. 047 farad reservoir capacitor.
(a) The peak-to-peak ripple voltage.
(b) The transformer secondary voltage if the total forward voltage
drop in the rectifier is 2 V at 2 A.
Q2. An aircraft electrical system operates at 115 volts at 400 hertz. It is to supply an average d.c. voltage of 28 volts and an average current of 20 A at a ripple factor of 0.005.
a) The r.m.s. ripple voltage.
b) A suitable value of smoothing capacitor.
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The solution covers a set of important calculations regarding the design of a simple DC power supply using a transformer, diode bridge and a smoothing capacitor. Calculation examples emphasize the estimation of ripple voltage parameters and how to determine the suitable smoothing capacitor value.
One simple setup of the DC power supply can be built using a transformer, full-wave diode bridge rectifier and a reservoir (smoothing) capacitor. The large output capacitor (C) is discharged through a load (R) with the time constant tau = R*C. If the time constant is very large compared to the period of the AC supply waveform (T), the capacitor voltage decrease can be approximated with a linear function. When this condition is satisfied, the calculations can be simplified. The relation tau >> T holds for the sets of parameter values ...