Double Field Revolving Theory

DOUBLE FIELD REVOLVING THEORY

From the principle, ie any alternating quantity can be resolved into two quantities which rotate in opposite directions and have half of the magnitudes. The alternating sinusoidal flux (ϕ_m) produced in the single phase induction motor can be represented by two revolving fluxes, each equal to half the value of (ϕ_m/2) the alternating flux and each N_s = 120ƒ/p in opposite directions by shown in fig 3.66.

The vectors a and b have been rotated by an angle +Ɵ and -Ɵ is shown in fig 3.67.

The resultant flux would be 2 × ϕ_m/2 × cos 2Ɵ/2

= ϕ_m cos Ɵ

After the quarter cycle of rotation that means Ɵ = 90°, fluxes a and b will be oppositely directed as shown in fig 3.68.

Now the resultant flux is zero.

After the half cycle rotation, which meansƟ = 180°, fluxes a and b will have resultant of -2 × ϕ_m/2 = -ϕ_m, is shown in fig 3.69

After three quarter of a cycle, that is Ɵ = 270°, again the resultant flux is zero is shown in fig 3.70.