Magnetization Curve - 170 kW, 250V, 850 rpm DC Shunt Generator 350 300 250 200 150 100 50 2 3 6 7 8 9 10 11 12 Field Current (A) Question 1 The figure above shows the excitation curve (including residual voltage) of a 170 kw, 250 V DC shunt generator at rated speed of 850 rpm. The generator has negligible (0 2) armature resistance and a shunt field coil resistance of 50 2. The variable Field Control Rheostat in series with the shunt field coil has variable resistance in the range of 0 - 25 0. Answer the following questions relating to this generator. Show (explain) your work (right), then select an answer from the choices provided. (a) What is the approximate value of the critical field circuit resistance? %3D (1) 95 0 (ii) (ii) (iv) (v) 85 0 75 0 65 Q 55 0 (b) What is the induced EMF( Eo) at rated speed with the rheostat set to its minimum resistance? () 322 V (i) 300 V (ii) 265 V (iv) (v) 250 V 50 V (c) What is the induced EMF( Eo) at rated speed with the rheostat set to its half way resistance? () (i) (iii) 325 V 265 V 250 V (iv) (v) 245 V 220 V What is the approximate value induced EMF( Eo) at a field current of 5.6 A and rotor speed of 630 rpm? (d) () (i) (i) (iv) (v) 375 V 335 V 300 V 275 V 200 V (e) What is the field current when the induced emf is 328 V and the rotor speed is 935 rpm? () (i) (ii) 8.4 A 7.4 A 6.1 A (iv) 4.8 A (v) 3.0 A (f) What is the rheostat resistance settings when the induced voltage is 300 V and the generator is turning at 120% rated speed? (1) (i) 12.65 0 10.47 Q Induced emf - Eo (V)