Tham khảo tài liệu '(mcgraw-hill) (instructors manual) electric machinery fundamentals 4th edition episode 2 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Appendix C Salient Pole Theory of Synchronous Machines C-1. A 480-V 200-kVA 60-Hz four-pole Y-connected synchronous generator has a direct-axis reactance of Q a quadrature-axis reactance of Q and an armature resistance of Q. Friction windage and stray losses may be assumed negligible. The generator s open-circuit characteristic is given by Figure P5-1. a How much field current is required to make Vt equal to 480 V when the generator is running at no load b What is the internal generated voltage of this machine when it is operating at rated conditions How does this value of EA compare to that of Problem 5-2b c What fraction of this generator s full-load power is due to the reluctance torque of the rotor Solution a If the no-load terminal voltage is 480 V the required field current can be read directly from the opencircuit characteristic. It is A. b At rated conditions the line and phase current in this generator is P 200 kVA IA Il -_ Tt-7 T A at an angle of V3 Vl 73 480 V 295 E Vộ RaI a jXq IA E 277Z0 Q A j Q a eA V Therefore the torque angle s is . The direct-axis current is Id IA sin 0 s ZS- 90 I d A sin Z- I d Z- A The quadrature-axis current is Iq IA cos 0 s ZS I q A cos E A q Therefore the internal generated voltage of the machine is E A Vộ RaI a jXd Id jXqIq Ea 277Z0 j j E A V E A is approximately the same magnitude here as in Problem 5-2b but the angle is about different. c The power supplied by this machine is given by the equation p-3Vộ E 3V2 Xd - Xq Ì P sin o sin 2o Xd 2 XdXq D_ 3 277 322 . o 3 277 2 - P _ - sin v I _ -7- I sin 2 J P kW kW kW The cylindrical rotor term is kW and the reluctance term is kW so the reluctance torque accounts for about 25 of the power in this .
