1 elifier with an AC source voltage of 230 V, 50 Hz. Assume continuous conduction Motor is controlled by a single-phase hal mode. Calculate (a) speed at a-60 and torque 1000 N-m, and (b) torque wt a 200 rpm. (Ans: (a) 383 rpm, (b) 3547 N-m) 60 and speed of Note: The output voltage of a single-phase half-controlled rectifier is given by √2v, T (1 + cos a) Q.3) A 220 V, 750 rpm, 200 A separately excited DC motor has armature and field resistances of 0.05 2 and 20 £2, respectively. Load torque is given by the expression T-500-0.2N N-m where N is the speed in rpm. Speeds below rated value are obtained by armature voltage control with full field, and the speeds above rated are obtained by field control at rated armature voltage. Armature is fed from a three-phase fully controlled rectifler with a AC source voltage (line-to- line) of 170 V, 50 Hz and the field is fed from a single-phase half-controlled rectifier with a single-phase AC source voltage of 250 V, 50 Hz. Drive operates under continuous conduction mode. Calculate firing angles of armature (aa) and field (ar) converters for speeds: (a) 600 rpm, (b) 1200 rpm. (Ans: (a) a, -40.3", a 17.28", and (b) a,-16.61°, a=76.4") Note: The output voltage of a single-phase half-controlled rectifier is given by √2v, TIRS V₁ = TE (1 + cos a) Q.4) A 220 V, 750 rpm, 200 A separately excited DC motor has an armature resistance of 0.05 2. The Motor is fed from a three-phase fully controlled dual converter operating in circulating current control mode. The line voltage of AC source is 400 V. When the motor operates in forward motoring, converter-A works as a rectifier and converter-B as an inverter. Calculate firing angles of converters A and B for the following operating points: (a) Motoring operation at rated torque and - 600 rpm, and (b) Regenerative braking operation at rated torque and 600 rpm. 107°) (Ans: (a) a=107°, ag= 73°, and (b) a₁ = 73°, ag=