Question

Problem 5 (10 points A 3 phase induction machine is mechanically coupled to a dc shunt machine. The rating and parameters of the machines are as follows: Induction machine 3 phase, 5 kVA, 208 V, 60 Hz, four-pole, 1746 rpm (equivalent circuit shown below) Air gap DC machine: (dc shunt machine shown below) 220 V, 5 kW, 1750 rpm R.-0.4 ?, Rf,-1000, Rfc-100? SW tw The induction machine is connected to a 3 phase, 208 V, 60 Hz supply, and the dc machine is connected to a 220 V dc supply. The rotational loss of each machine of the M-G set may be considered constant at 225W The system rotates at 1710 rpm in the direction of the rotating field of the induction machine Determine the mode of operation of the induction machine Determine the current taken by the induction machine Determine the real and reactive power at the terminals of the induction machine and indicate their directions Determine the copper loss in the rotor circuit Determine the armature current (and its direction) of the dc machine a) b) c) d) e)

Answer 1

Given Induction machine R_1 = 0.25 ohm R_2 ' = 0.35 ohm x_1 = 0.55 ohm x_2 ' = 1.1 ohm x_m = 39 ohm critical Diagram DC -machine DC short machine as shown in below 220 v, 5 k w 1750 r p m where R_a = 0.4 ohm R f w = 100 ohm k f c = 100 ohm rightarrow The Induction machine is connected to 3 phase, 208 v, 60 Hz rightarrow The DC machine is connected to 220 v de supply Determine the mode of operation Give the system the rotates in the direction of the rotating field 'g' the Induction machine so the mode of operation of ' T' the Induction machine is Induction motor find current taken by Induction machine we know that the formula of current (I) I_1 = 208 v/squareroot 3 times 2 s = frequency = 60 Hz