Question

Be sure that you have enough knowledge and right answer with step by step solution and answer all three parts. more importantly (c) if you you solve wrong or half question leads to dislike. be sure that you have able to solve (986) Example 9 A 3-phase, 6-pole, 50 Hz, Schrage motor has duplex lap connected tertiary winding and a 3-phase secondary winding. The primary winding has total 180 turns with a coil span of five-sixths of full pitch. The secon- dary has total 240 turns arranged in 4 parallel paths and coil span of four-fifths of full pitch. The tertiary has total 180 full-pitch turns. The secondary carries 100 A. Neglect exciting current and assume no brush displacement. Brush separation is 80° (elec.) and the operation is at sub- synchronous speed. The leakage reactance per phase of the primary when running as an induction motor is 8 ohm, Calculate: (a) the no-load speed, (b) the primary current, (c) the leakage reactance drop per phase in the primary winding.

Answer 1

(a) Calculate the effective number of turns per phase in primary. Niep = Nike1 = 180 cos TT -- = 155.88 turns Calculate the effective number of turns per phase in secondary. Nzet = N2k2 240 4 5 = 16.18 turns Calculate the effective number of turns per phase in tertiary. 80 == cos T - - sin Nzeg = Nzk380 =- = 180 cos(1 - 1) = 2.89 turns Calculate the slip at no load. E; N3ell Ez Neo 2.89 16.18 = 0.18 Calculate the no load speed. no = n(1-5.) =1000(1–0.18) = 820 rpm Therefore, the no-load speed in 820 rpm.

(b) Calculate the primary current, 11. (16.18 =100 55.34 = 29.23 A (c) Calculate the leakage reactance drop per phase in primary winding. 1 Drop=4 - 8,11 - N3ef Net 1. 2.89 (0.8) (29.23). 16.18 = 28.52 A