Flux density around translator

It is possible to formulate and analyse the equivalent magnetic circuit of the flux flow out of a single radial pole segment, width d9, into the adjacent pole, Figure 5.1. All the flow is assumed to emanate from the midpoint of the magnet and flow through the entire width of the magnet section into the steel spacer, thus ignoring leakage through the magnet air border. In combination with the concept of effective airgap introduced in Chapter 3, the flux density across the width of the steel / air border is assumed to be constant whilst that above the magnet / air border is assumed to be zero, Figure 5.2. All the steel is assumed to have an infinite permeability.

Figure 5.1: Equivalent circuit of radial segment
Figure 5.2: Assumed flux flow in air core machine

The reluctance of the two effective airgaps and each half of the magnet is given in (5.1) and (5.2) respectively.

^odA2

^0nRmWsd^

The total reluctance of the flux path from each magnet may hence be calculated by summing two of each of these components (giving Sm+2Sg) and integrating for 9 between 0 and 2n, which will allow the flux flow from one pole to be as given in (5.3) when subjected to the mmf from the magnet with a remnant flux density of Br.

22 n Br wmWsRm

The flux derived above divided by the area from which it emanates represents the value of flux density at the surface of the rotor, Bg, given in (5.4).

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