Tham khảo tài liệu 'electric machinery fundamentals (solutions manual) part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | sin s 2 sin l 2 2 E V RAI A Ũ XS1 A XS1 A RaIs V E 2 _ RaIs sin I 2 RaIa cos l X SI A sin I V XS I A cos If we examine these three cases we can see that the only difference among them is the sign of the term sin l . If l is taken as positive for lagging power factors and negative for leading power factors in other words if I is the impedance angle then all three cases can be represented by the single equation V E 2 _ RaIs sin I 2 RaI a cos l X SI A sin I V XS Ia cos A MATLAB program that calculates terminal voltage as function of impedance angle is shown below M-file prob5 M-file to calculate and plot the terminal voltage of a synchronous generator as a function of impedance angle as PF changes from lagging to leading. Define values for this generator EA 509 Internal gen voltage I 361 Current A R R ohms X XS ohms Calculate impedance angle theta in degrees theta th theta pi 180 In radians Calculate the phase voltage and terminal voltage VP sqrt EAZ 2 - X. I. cos th - R. I. sin th .A2 . - R. I. cos th - X. I. sin th VT VP . sqrt 3 Plot the terminal voltage versus power factor figure 1 plot theta abs VT b- LineWidth title bfTerminal Voltage Versus Impedance Angle xlabel bfImpedance Angle deg ylabel bfTerminal Voltage V axis 0 260 300 540 grid on hold off The resulting plot of terminal voltage versus impedance angle with field and armature currents held constant is shown below 134 5-21. Assume that the generator is connected to a 480-V infinite bus and that its field current has been adjusted so that it is supplying rated power and power factor to the bus. You may ignore the armature resistance Ra when answering the following questions. a What would happen to the real and reactive power supplied by this generator if the field flux and therefore E A is reduced by 5 . b Plot the real power supplied by this generator as a function of the flux as the flux is varied from 75 to 100 of the flux at rated .
