Tham khảo tài liệu 'electric machinery fundamentals power & energy_13', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | c If the armature current is 40 A then the effective field current contribution from the armature current IA -15- 40 A A Nf 1000 and the IA Ra RS voltage drop is IA Ra RS 80 a Q 8 V . The location where the triangle formed by IA and IaRa exactly fits between the EA and VT lines corresponds to a terminal Nf voltage of 116 V as shown below. 259 A MATLAB program to locate the position where the triangle exactly fits between the EA and VT lines is shown below. This program created the plot shown above. M-file 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 if_values p97_mag 1 ea_values p97_mag 2 n_0 180 0 First initialize r_f 20 r_adj 10 r_a i_f 0 6 n 1800 n_f 1000 n_se 20 the values needed in this program. Field resistance ohms Adjustable resistance ohms Armature series resistance Field current A Generator speed r min Shunt field turns Series field turns ohms Calculate Ea versus If Ea interp1 if_values ea_values i_f Calculate Vt versus If Vt r_f r_adj i_f Calculate the Ea values modified by mmf due to the armature current 260 i_a 20 Ea_a interp1 if_values ea_values i_f i_a n_se n_f Find the point where the difference between the enhanced Ea line and the Vt line is 4 V. This will be the point where the line Ea_a - Vt - 4 goes negative. diff Ea_a - Vt - 4 This code prevents us from reporting the first unstable location satisfying the criterion. was_pos 0 for ii 1 length i_f if diff ii 0 was_pos 1 end if diff ii 0 was_pos 1 break end end We have the intersection. Tell user. disp Ea_a num2str Ea _a ii V disp Ea num2str Ea ii V disp Vt num2str Vt ii V disp If num2str i_ f ii A disp If_a num2str i_ f ii i_a n_se n_f A Plot the curves figure 1 plot i_f Ea b- LineWidth hold on plot i_f Vt k-- LineWidth Plot .