Question

Below shows a graph of speed vs torque characteristic of a 3-phase induction motor. Describe how the induction motor speed varies as the motor torque increases.

Graph of Speed vs Torque Characteristic Torque (N.m) 0 2 00 400 600 1000 1200 1400 1600 800 Speed (r/min)

Answer 1

characterstics of 3 pk IM Torquan 35 Consider in Grease & Decrease 9- 81 205- - - - - I Qw yo belo 100 200 luw Broupm N=NST N=0 from figure, Tmax occur at nearly 650 rpm approximately Tmax = 3.550-m Given that, N=Ns = 150 pm for frequency f= 50H3 Then 4 poles are possible. Characterstics : at s=0 N=NS SER2 TE 180 em atins R22+(Sx2 at Nans slip becomes Zero Torque o for lower values of stif 56202 Ilo Tem = QuNS 127 S dry low R2 7 (5+2)² = neglect (x² - low Tema SEZRY at R2 Temas approximately from point a tod: slip slip in Greases, speed decoreases, Torque increases N= Ngli-s), Ship f, (1-5), NI
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s from point atod. T A NY follows innove relation at T- Tmax. (or) S- Sun: at point 'D' T = Tmax occurs T= 355N-m speed is at Torque in maximum = 650 rpm. up to this duason, motor opearates as a stable region beyond This region induction motor behaves as unstable OLSCI (Higher value of slip) S Tem= 1 st B2 TS+)? (5x23² >> 0Z te tem a PP I sh ,N=(1-sp NS ST NY TV from point e tue NL TV linear relation TURINN at s=1: NO NENS(1-5) = NS (1-1) = 0 rpm Tst = 180 % - Zitos" R4 x 2 Here speed is zero, Tst adjusts from final analysis: at N=0, There will be starting torque from & to D, speed in Greases gradually & Torque also increases gradually from otoA speed in Greases but Torque decreases
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