Page 272 - Solutions Manual to accompany Electric Machinery Fundamentals

A MATLAB program to locate the position where the triangle exactly fits between the E A and V T lines
is shown below. This program created the plot shown above.

% M-file: prob8_27b.m
% M-file to create a plot of the magnetization curve and the
% M-file to create a plot of the magnetization curve and the
% field current curve of a cumulatively-compounded dc generator
% when the armature current is 20 A.

% Get the magnetization curve. This file contains the
% three variables if_values, ea_values, and n_0.
clear all
load p87_mag.dat;
if_values = p87_mag(:,1);
ea_values = p87_mag(:,2);
n_0 = 1800;

% First, initialize the values needed in this program.
r_f = 20; % Field resistance (ohms)
r_adj = 10; % Adjustable resistance (ohms)
r_a = 0.21; % Armature + series resistance (ohms)
i_f = 0:0.02:6; % Field current (A)
n = 1800; % Generator speed (r/min)
n_f = 1000; % Shunt field turns
n_se = 25; % Series field turns

% Calculate Ea versus If
Ea = interp1(if_values,ea_values,i_f);

% Calculate Vt versus If
Vt = (r_f + r_adj) * i_f;

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