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(McGraw-Hill) (Instructors Manual) Electric Machinery Fundamentals 4th Edition Episode 2 Part 4

Tham khảo tài liệu '(mcgraw-hill) (instructors manual) electric machinery fundamentals 4th edition episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | the line Ea_ar - Vt - i_a r_a goes negative. i_a 0 1 37 for jj 1 length i_a Calculate the equivalent field current due to armature reaction. i_ar i_a jj 50 200 n_f Calculate the Ea values modified by armature reaction Ea_ar interp1 if_values ea_values i_f - i_ar Get the voltage difference diff Ea_ar - Vt - i_a jj r_a 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 Save terminal voltage at this point v_t jj Vt ii i_l jj i_a jj - v_t jj r_f r_adj end Plot the terminal characteristic figure 1 plot i_l v_t b- LineWidth 2.0 Xlabel bf itI_ L rm bf A ylabel bf itV_ T rm bf V title bfTerminal Characteristic of a Shunt DC Generator w AR hold off axis 0 50 0 120 grid on 255 The resulting terminal characteristic is shown below 9-26. If the machine in Problem 9-25 is running at 1800 r min with a field resistance Radj 10 Q and an armature current of 25 A what will the resulting terminal voltage be If the field resistor decreases to 5 Q while the armature current remains 25 A what will the new terminal voltage be Assume no armature reaction. Solution If IA 25 A then IARA 25 A 0.18 Q 4.5 V. The point where the distance between the Ea and VT curves is exactly 4.5 V corresponds to a terminal voltage of 104 V as shown below. 256 If Radj decreases to 5 Q the total field resistance becomes 29 Q and the terminal voltage line gets shallower. The new point where the distance between the EA and VT curves is exactly 4.5 V corresponds to a terminal voltage of 115 V as shown below. 9-27. Note that decreasing the field resistance of the shunt generator increases the terminal voltage. A 120-V 50-A cumulatively compounded dc generator has the following characteristics Ra RS 0.21 Q Nf 1000 turns Rf 20 Q Nse 20 turns Radj 0 to 30 Q set to 10 Q nm 1800 r min The machine has the magnetization curve shown in Figure P9-7. Its equivalent circuit is shown in Figure .