Question

Problem Solving: 1. A 220V, 4-pole, 60Hz, 1-phase induction motor has an effective rotor resistance and leakage reactance of 0.5 Ohms and 5 ohms respectively. It is running at a speed of 1,800 rpm. Determine: a. Frequencies of forward and backward rotor current components b. Relative magnitudes of forward and backward fluxes. Neglect magnetizing current and stator impedance. A 220-W, 2-pole, 115-V, 60-Hz single-phase induction motor delivers rated output at a slip 10%. The total copper loss at full load is 25 watts. Calculate the full-load efficiency and the rotor copper loss caused by the backward field. Rotational losses maybe assumed to be 25 watts. Neglect stator copper loss.

Answer 1

NG = 120xf - 120xc -ở 18 00 rpM. N = 1800rpm Cgiven) G. NG-N Ns K100 - 01. førcoard Glip G .0 ; Bachcoard Glep = 2--. @ freguency of forcoard rotor Currennt Coroponent - Ox 60 =0. I freguency of Backward rotor corrent Componerst - 120H2, (2- SE) xGO negle ctiving Gtator impedance and magnebiGing Current. Be'/26f Bd/26b ocd/26b. 99%/24 Given B2 = Be=0.52 Bea 0.25 a.25/o {2.5/a 2p+2b because 2 =. F0.25/2 Go Belative matgnitedes of -forcoard and reverBe fluxes phase difference Gummary : cohen Glep G-o the re t6 no Hco Gtator flux and rotor flux and there i6 no torgue Ecerted on rotor and rotor doeGnot rotate.(I=0), HocoEver practically the Glip Carst bezo CS IT That ts cohy et (6`called as asynchrone motor. CamScanner

rated output = 220B60. V= 11 5. f = 60HZ. - 0.1 25 coatts. loGGe6 atfoll load - Copper Fotor Copper LOGGEG caused by backoard field = 2 Effi cíency= ? Gtator LOGGEG =0. Copper Botattonal loGGe6 E25 coatts. I?CBf-Bb), P/p to Pf-Pb rotor ConGtant loGses) motor rated olp = ( Polp of rotor - Scanned with CS CamSca PA0 = (P olp rotor 25 )

220+25 soy coatt. developed poccer at rotor (Pf- Pb) 1- %3D Botor ilp pocoer <pf-Pb) Gtator /p poLoer = Botor (nputpocoer = Pt Pb. Pf -Pb. [Because Gtator copper negle cted) loGGeG are Pdeveloped (Pf-Pb) 245 = 272 222 0.9 1-S Ghaft op pocoer Full load Efficiercy X100. 972.222 Gtator p pocoer cs Scanned with CamScanner రిం: . " Full load

Total rotor Copper loGses Botor tnput pocoer- pocoer developed at rotor. Botor Copper loGses Pf- Pb - Cpt-Pb)C4-5) - Pf - Pb-(Pf - Pb)- 6 CPf-Pb] -(Pf-Pb)S. > PfG - PbG. = 27.222 Botor copper loGGe6 due to backcoard field. 27222- 25 = 2.22200ath Scanned with CS CamScanner %3D