Page 318 - Solutions Manual to accompany Electric Machinery Fundamentals

18 2  1 1   /6
V  V t  sin2 t 
rms M  
  2 4  
0
18    1   3 9 3
V  V  sin  V   1.6554 V
rms M   M M
 12   4  3  2 4 
The resulting ripple factor is

 V  2  1.6554 V  2
r    V rms    1 100%     1.6540 V  M   1 100%   4.2%
M
DC
The ripple can be calculated with MATLAB using the ripple function developed in the text. We must
right a new function fullwave3 to simulate the output of a three-phase half-wave rectifier. This output
is just the largest voltage of  tv A ,   tv B , and   t at any particular time. The function is shown
v
C
below:

function volts = fullwave3(wt)
% Function to simulate the output of a three-phase
% full-wave rectifier.
% wt = Phase in radians (=omega x time)

% Convert input to the range 0 <= wt < 2*pi
while wt >= 2*pi
wt = wt - 2*pi;
end
while wt < 0
wt = wt + 2*pi;
end

% Simulate the output of the rectifier.
a = sin(wt);
b = sin(wt - 2*pi/3);
c = sin(wt + 2*pi/3);

volts = max( [ a b c ] ) - min( [ a b c ] );
The test driver program is shown below.

% M-file: test_fullwave3.m
% M-file to calculate the ripple on the output of a
% three phase full-wave rectifier.

% First, generate the output of a three-phase full-wave
% rectifier
waveform = zeros(1,128);
for ii = 1:128
waveform(ii) = fullwave3(ii*pi/64);
end

% Now calculate the ripple factor
r = ripple(waveform);

% Print out the result
string = ['The ripple is ' num2str(r) '%.'];
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