Question

A 100 kW, 500 V, 2000 r.p.m separately excited d.c. motor is energized from a 400 V, 50 Hz, three phase source through a three phase full converter. The voltage drop in conducting thyristors is 2 V. The d.c. motor armature resistance is 0.1 Ω, motor constant is 1.6 V-s/rad, rated armature current is 210 A and no-load armature current is 10% of rated current. Determine the following:

i) Motor terminal voltage at a firing angle of 30

ii) No load motor speed at a firing angle of 30

iii) The firing angle for a speed of 2000 r.p.m at rated armature current

Answer 1

* A 100kw, 500V, 2000 ypm seperately excited de motos és Power Po=100x10311 Ra=011 Verms : 400 freq&f= 50 Hz K= 116 Yos/rad Vor-500V M, 2000rpm Vd=2v Ta,= 210A Iany : 10% of Iar 10% of 210 I and = A. i) Motor terminal voltage at a firing angle of 30% d=30° Vol. 3 Nima cosa 3 (73 Verms-2) Cos 30º =) 3(11(400) - 2) (0.15425) ग Vol = 466,16 V motor terminal v Hg, *) No lood motor speed at a firing angle of 30* Eb = Vo - la, Ra - 466.16 y at 30° - 500 - (210 x0,11) Ebg = vo- I andra =466,16 - (212011) Eb, 479 v Eb, 464,06 V la'R 'Eó directly proportional to mo. Ebz 2 kW, > 10,- 464,06 к 116 ONL = 2 LOL = 290.03 radis LONL: 21 NNL 60x290,03 - NALE GO 2X T Mo load motor speed. NAL= 2770 rpm ii) The firing angle for a speed of 2000 rpm at rated armature Wikit Iaz Ia, Corrent. Nuo Eь, 2 k L0, 277 None 2 K ( 2 1 2 211 x 2000 GO Eb22) 335,10 V Voga Eb2 + Ia, ha = 335110 + (210x010) ») 335110 + 211 You?) 358,10 V Vo2 =3Vme cosa ~ 356.10, 3(13400) - ) COS O Q: cos' (0.66) do 48,580 Scanned with CamScanner

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