Given Data Voltage Va = 200 v Armature Resistance Ra = 0.5Ω Armature Current Ia = 20 A Induced EMF = Ea = ? The Induced EMF of a DC machine working as a Motor is Ea = Va − IaRa Ea = 200 − 20 × 0.5 Ea = 190 V
The total number of the conductor in stranded cable is given by N = 3x2 − 3x + 1 Where x = no. of layer For layer 1 N1 = 3(1)2 − 3(1) + 1 N1 = 1 For layer 2 N2 = 3(2)2 − 3(2) + 1 N2 = 7 In layer 2 no. of conductor = N2 − N1 = 7 − 1 = 6 For layer 3 N3 = 3(3)2 − 3(3) + 1 N3 = 19 In layer 3 no. of conductor = N3 − N2 = 19 − 7 = 12
Sudden changes of load on synchronous motors may sometimes set up oscillations that are superimposed upon the normal rotation, resulting in periodic variations of a very low frequency in speed. This effect is known as hunting or phase-swinging.
Hysteresis Loss = Kh × BM1.67 × f × v watts where Kh = Hysteresis constant depends upon the material Bm = Maximum flux density f = frequency v = Volume of the core Hence the hysteresis loss does not depend upon the ambient temperature.
The reluctance of any part of a magnetic circuit may be defined as the ratio of the drop in magnetomotive force to the flux produced in that part of the circuit. It is measured in ampere-turns/Weber and is denoted by S. Reluctance = m.m.f ⁄ flux
EXAMIANS