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.
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
Given Inductance L = 2 H Rate of change of current di/dt = 5 A/sec Self induced EMF = − (Rate of change of current × Inductance) = −L(di/dt) = −(5 × 2) = −10V
Mutual inductance between two coupled coils is given by the relation M = K√L1L2 Where L1L2 = Inductance of the coil K = Coefficient of coupling When K = 1 coils are said to be tightly coupled and if K is a fraction the coils are said to be loosely coupled. Here Kmax =1 Kmin =0 ∴ m ≤ (L1 L2 )0.5
EXAMIANS