Question

QUESTION 2 [25 MARKS] a) Describe what will happen to the induction motor when the rotor speed is the same as the rotating magnetic field speed. 15 MARKS b) The following data in Table 2 was obtained from the no-load test, locked rotor test and DC test of a three-phase delta-connected, 450 V, 2-pole, 60 Hz, wound-rotor induction motor. The locked rotor test was done at 15Hz. No-load test Vyt = 450 V Ini - 30 A PNL-4.6 kW Table 2 Locked rotor test Vir - 36 V lur - 60 A Pur - 2.6 kW DC test Vpc = 12 V Ipc - 50 A Determine the equivalent circuit parameters of the induction motor based on the information given in Table 1. [10 MARKS Determine the starting current by assessing the per-phase equivalent circuit 15 MARKS ii. iii. Compare the starting current and the stator current when the motor runs at 2% slip (5 MARKS

Answer 1

Que a Slip s = NS-N- NS if Ns Nr than S=0 and the relative speed stator field will be zew. So motor stops Boleting, between sobor and so Torque will be zeu. 5 30, delat Cormeeled, 4500, 2 pole , Gokzis rotor test was done at 15Hz: De test No load test locked sotor test 36V 12V HLR > Voc - VAL = 4500 Inc = 50A INL = 30 A ILR - 60A PLA = 2.6kw PNL -4.6KW 77 p Step DC test :- RICAC) 1-5 RI(DC). RI (AC) 1-5 X 12 ང 0-36 n 50 Step ③ Block Rotor fest cim non RNL ph 3 You

ZAILE VNL 450 INLB 30/13 IZAL ZNL = 25.98 RNL WNL 4.68looo 5.111 3 INZ = 3* ( 30/5372 3 XNL = ZN 2² _ RN2² 25. 473 m Step 6:- Block Rotor LR ? VLR Tals 30 3 1.0992 60/52 ZR=1.03 92 RLR = 260o WLR IR = o 7 22r ar v 602 XLR - 11.0392 1,039 22-0-7222 XLR 0.747 0.747 x 60 XLR at 60 H2= 2.989 15 XLR g. 992

X, xo XLR 2 X1 = 1.5or and XNL =xit XM Xu = XNL-X, 25.473 1.50 Xu - 23.973 n 2 Xu and B' = ( ReR – RI) ( *** Kad = ( 0-722– 0.36) ( 23.97 1.504 23.97 Ral 0.4087 Part 6 ('ب 0-36 1:50 0.4087 11.50 1000 my son R jxy Rg jXg Von ; 23.97 jxu R=0.362 Xu = 93.97 i Rg' = 0.4087n X - _X = 1.500

(۱) at Starting Slip s=1 so Grosent Ist Uph z N = 0:36 6 +31:50 50+ ((123.92) *+ (0 v057 +3 1.60)")" z = 3.005/76.102 So Ish = 450 3.005Z 76:102 Ish = 149. 73_-764102 figure in shown above. If S = 2 =0:02 100 then equivalent ckt is 31.50 ชชชชา Ri jx, j1.50 Vph 6.36 ex 1 23.97 Ra jxu 20-435 1 Zpn 0.30+31,50 + [1395 | 93.97) + (20.485+1.50) 16.35_45.93 Zph =

I Iph Vph Zph 450 16- 35/ 45.93 Inh = 27. 53 3 / -45.930 Amp Current at a % slip so 149.73 Ist (Ipn at al common 5.44 27.53 so Grosent is 5.44 times than Arosent at starting 29. sup.