Working Principle of Shaded-Pole Induction Ammeter

Working Principle of Shaded-Pole Induction Ammeter Points : Working Principle of Shaded-Pole Induction Ammeter Shows the shaded-pole disc type induction ammeter, only single flue producing winding is used. The flux produced by this winding is split up in to two fluxes Φ₁ and Φ₂, which are made to have the necessary phase difference of by the device.

The portions of the upper and lower poles near the disc “D” are divided by a slot in to two halves one of which carries a closed “shading” winding or ring. This shading winding or ring acts as a short-circuited secondary and the main winding as a primary. The current induced in the ring by transformer action retards the phase of flux Φ₂ with respect to that of Φ₁ by about 50°. The two fluxes Φ₁ and Φ₂, passing through the unshaded and shaded parts respectively, react with eddy currents “i₂” and “i₁” respectively and so produce the net driving torque.