nzart-exam-generator/files/N22.TXT

% FILENAME = N22.TXT
% Regulated Power Supplies
% Release version 3, October 2001
% Q 4, 10 corrected 6 Mar 2012

%Question: 1 
#22.1 The block marked 'Filter' in the diagram is to: 
<img src = "regps.gif" align = center width = 511 height = 129> 
<totallines = 13 >

filter RF radiation from the output of the power supply 

smooth the rectified waveform from the rectifier 

act as a 50 Hz tuned circuit 

restore voltage variations 

% ans 2 

%Question: 2 
#22.2 The block marked 'Regulator' in the diagram is to: 
<img src = "regps.gif" align = center width = 511 height = 129> 
<totallines = 13 >

regulate the incoming mains voltage to a constant value 

ensure that the output voltage never exceeds a dangerous value 

keep the incoming frequency constant at 50 Hz 

keep the output voltage at a constant value 

% ans 4 

%Question: 3 
#22.3 The block marked 'Transformer' in the diagram is to: 
<img src = "regps.gif" align = center width = 511 height = 129> 
<totallines = 13 >

transform the incoming mains AC voltage to a DC voltage 

ensure that any RF radiation cannot get into the power supply 

transform the mains AC voltage to a more convenient AC voltage 

transform the mains AC waveform into a higher frequency waveform 

% ans 3 

%Question: 4 
#22.4 The block marked 'Rectifier' in the diagram is to: 
<img src = "regps.gif" align = center width = 511 height = 129> 
<totallines = 13 >

turn the AC voltage from the transformer into a fluctuating DC voltage 

rectify any waveform errors introduced by the transformer 

turn the sinewave output of the rectifier into a square wave 

smooth the DC waveform 

% ans 1 

%Question: 5 
#22.5 The block marked 'Regulator' in the diagram could consist of: 
<img src = "regps.gif" align = center width = 511 height = 129> 
<totallines = 13 >

four silicon power diodes in a regulator configuration 

two silicon power diodes and a centre-tapped transformer 

a three-terminal regulator chip 

a single silicon power diode connected as a half-wave rectifier 

% ans 3 

%Question: 6 
#22.6 In the block marked regulator in the diagram below, a reversed diode may be present across the regulator.  Its job is to
<img src = "regps.gif" align = center width = 511 height = 129> 
<totallines = 15 >

Block negative voltages from appearing at the output 

Blow a fuse if high voltages occur at the output

Blow a fuse if negative currents occur at the output

Bypass the regulator for higher voltage at its output compared to its input

% ans 4 

%Question: 7
#22.7 A power supply is to power a solid-state transceiver. A suitable 
over-voltage protection device is a: 

crowbar across the regulator output 

100 uF capacitor across the transformer output 

fuse in parallel with the regulator output 

zener diode in series with the regulator 

% ans 1 

%Question: 8 
#22.8 In a regulated power supply, the 'crowbar' is a: 

means to lever up the output voltage 

circuit for testing mains fuses 

last-ditch protection against failure of the regulator in the supply 

convenient means to move such a heavy supply unit 

% ans 3 

%Question: 9 
#22.9 In a regulated power supply, 'current limiting' is sometimes used to: 

prevent transformer core saturation 

protect the mains fuse 

minimise short-circuit current passing through the regulator 

eliminate earth-leakage effects 

% ans 3

%Question: 10 
#22.10 The purpose of a series pass transistor in a regulated power supply is 
to: 

suppress voltage spikes across the transformer secondary winding 

work as a surge multiplier to speed up regulation 

amplify output voltage errors to assist regulation 

Allow for a higher current to be supplied than the regulator would otherwise allow

% ans 4