Tham khảo tài liệu '(mcgraw-hill) (instructors manual) electric machinery fundamentals 4th edition episode 2 part 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | VTH ---- i V j30Q V V TH R j X1 XM ộ Q j Q 30 Q v a If losses are neglected the induced torque in a motor is equal to its load torque. At full load the output power of this motor is 50 hp and its slip is so the induced torque is nm 1 - 1800 r min 1732 r min tm T . 50 N m 1732 r min Ĩĩ-ĩĩd Ịsá v 7 1 r 60 s The induced torque is given by the equation 3V2 R 5 In 2 T. ind 2 2 Rync RTH R2 s XTH X2 Substituting known values and solving for R2 5 yields 3 262 V 2R 5 N m -------- z v 7 2 -------------------- rad s R 5 2 38 774 205 932 y 5 R2 5 R2 5 2 R2 5 5 R2 5 2 R2 5 R 2 R R - R 0 5 5 R 5 R2 Q Q These two solutions represent two situations in which the torque-speed curve would go through this specific torque-speed point. The two curves are plotted below. As you can see only the Q solution is realistic since the Q solution passes through this torque-speed point at an unstable location on the back side of the torque-speed curve. 195 b The slip at pullout torque can be found by calculating the Thevenin equivalent of the input circuit from the rotor back to the power supply and then using that with the rotor circuit model. The Thevenin equivalent of the input circuit was calculate in part a . The slip at pullout torque is 5 max 5 max 7 TH2 XTH X2 2 Q ọ 7 Q 2 Q Q 2 The rotor speed a maximum torque is pullout 1 - 5 sync 1 - 1800 r min 1454 r min and the pullout torque of the motor is 3VTH T ------------------ 2 sync RTH RTH XTH X2 T 3 262 V 2__ max 2 rad s Q 7 Q 2 Q Q 2 Tmax 448 N m c The starting torque of this motor is the torque at slip 5 1. It is 3V R 5 T __TH 2_ Tind 2 2 . Rth RJ 5 Xth X2 _ _ 3 262 V 2 Q d rad s Q 2 .
