Emf calculation

The emf induced in the VHM is dependent on the rate of change of flux due to magnet excitation, which means the equivalent magnetic circuit is similar to that of Figure 4.2 used to derive the shear stress, but with NI replaced with mmf from the magnets, or Hctm (defined previously in (3.5) ) as shown in Figure 4.3.

Figure 4.3: Equivalent circuit for VHM with magnetic excitation only

The flux flow due to one magnet only, may now be found in a similar manner as (4.2), giving (4.3). This expression considers only the flux flowing in the tooth region and thus represents the case when the magnet and teeth are fully aligned and leakage between two adjacent magnets is ignored, a highly simplified scenario.

Where Am = area of one magnet(m2)

If this is assumed to be the peak, (m, of a sinusoidal flux flow dependent on position, x, having a period of double the magnet width, then the flux flow through an entire face and its resultant emf can be expressed as (4.4).

V wm J vv m number of magnets mounted on stator face Combining (4.3) and (4.4) whilst remembering that Am = wmL, allows the relationship for peak emf given in (4.5) to be deduced.

Where n

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