A 50-hp, 200 V, 13.5 A, 1160 rpm., 60 Hz, wound rotor induction motor has the following equivalent-circuit parameters: R, = 2.22 0; R,' = 2.97 Q; X, = 14.2 Q and X'; = 324 Q The effective turns ratio is 1.22 and k = 0.979. a.) Determine the external rotor-circuit resistance per phase required to hold down, the starting current to three times the rated value. b.) Determine the speed at which the motor would developed an internal torque equal to 125% of the rated torque with this starting resistance still in circuit. Use: R;/S

23. As load is increased from no load to full load on a 3-phase squirrel-cage induction motor, what happens to the ..

With the aid of diagrams describe the basic topology of a wound field 3 phase synchronous generator and outline the relationship between the excitation voltage and rotor current. Q2 (a) (b) Outline with the aid of a suitable diagram the necessary power conversion stages required to interface a small permanent magnet (PM) generator to a stand alone DC system. A star connected 3 phase wound field synchronous generator with a synchronous reactance of 20 N is connected to a 6.6 kV (phase voltage) grid and supplies 1.5 MW at 0.95 lagging power factor at its terminals. Calculate the phase current and resultant voltage across the synchronous reactance (Vxs), and from a scaled phasor diagram graphically determine the required excitation voltage (Eph) and load angle (8). (c) The load is now increased to 3 MW with the Excitation Voltage kept constant. Using the phasor diagram drawn in part (c) graphically determine the resultant phase current, power factor and load angle. (d)