Answer Happy

(b) Figure 5 shows a set of Motor-Generator using two synchronous machines. The MG set draws 36 A current at 0.85 lagging power factor from a three phase supply of 415 V. The mechanical coupling between the two machines is not well maintained, resulting in 1 % of power loss. The output of the generator is connected to a current driven load with 35 A with 0.766 lagging power factor. The torque angle of the load (angle between the load current and the back erf of the generator) is 42º. The field current of the generator is adjusted so that the output voltage is 415 V at no load condition, and kept constant afterwards. Determine; i) The back emf, E, of the generator when the load is connected ii) The back emf, E, of the motor during the operation iii) The efficiency of the motor, 17. iv) The energy loss in the coupling, Pl.compling v) The rotational speed of the shaft in rad/s, vi) The input torque received by the generator, ting 122 Marks) (CO2, POI, C4) 415 V 50 Hz 36 A 0.85 p.f. lagging Synchronous motor Synchronous generator Coupling (1% loss) Load Vy - 415 V E,=? 50 Hz, 4 poles P,+Pc - 1332 W X, -0.5 R 0.22 Y-connected V, 415 V E, Vo_e_lood 50 Hz, 4 poles P, + Pc 1000 W X, -0.412 R-0.12 Y-connected I-35 A p.f. = 0.766 lagging y 42