Page 249 - Solutions Manual to accompany Electric Machinery Fundamentals

8-19. A series motor is now constructed from this machine by leaving the shunt field out entirely. Derive the
torque-speed characteristic of the resulting motor.
SOLUTION This motor will have extremely high speeds, since there are only a few series turns, and the
flux in the motor will be very small. A MATLAB program to calculate the torque-speed characteristic of
this motor is shown below:

% M-file: prob8_19.m
% M-file to create a plot of the torque-speed curve of the
% a series dc motor. This motor was formed by removing
% the shunt field from the cumulatively-compounded machine
% of Problem 8-17.

% Get the magnetization curve. Note that this curve is
% defined for a speed of 3000 r/min.
load p86_mag.dat;
if_values = p86_mag(:,1);
ea_values = p86_mag(:,2);
n_0 = 3000;

% First, initialize the values needed in this program.
v_t = 240; % Terminal voltage (V)
r_f = 200; % Field resistance (ohms)
r_adj = 120; % Adjustable resistance (ohms)
r_a = 0.14; % Armature resistance (ohms)
i_l = 20:1:100; % Line currents (A)
n_f = 1500; % Number of turns on shunt field
n_se = 15; % Number of turns on series field

% Calculate the armature current for each load.
i_a = i_l - v_t / (r_f + r_adj);

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