Pole Window Estimate Using FEMM Modelled String

[aquin43]

I constructed a FEMM model of a magnetised string using the axisymmetric mode.
The model consists of a series of 1mm long magnets of 0.45mm diameter with magnetisations chosen so that the internal flux pattern in the string falls within the range measured by M Zollner of POTEG.

By repeatedly setting the magnetisations of all except a chosen symmetric pair of magnets to zero, it was possible to plot the relative radial flux contributed by each pair of 1mm lengths of the string at the centre of the surface of a notional pole. The pole position chosen was 6mm from the string. Flux radial to the string is axial to the pole.

The assumed magnetising pole is a Stratocaster magnet. I used the Octave FEMM interface that allows FEMM drawing and analysis to be programmed from Octave.

Arthur

[ms]

Are these the data Zollner measured with the coil moved along the string?  That is, similar to figure 5.4.10 of POTEG?

[aquin43]

May 16, 2020 9:38:20 GMT -5 ms said:

Are these the data Zollner measured with the coil moved along the string?  That is, similar to figure 5.4.10 of POTEG?

Yes. It is also similar in form to the magnetisation of a plate over a magnet in 2D FEMM. The magnetisation array is tweaked by hand to achieve a similarly shaped curve. The absolute values are arbitrary; only relative values are considered and all materials have linear magnetisation characteristics.

The curve for the pole shows one side of a symmetrical arrangement with the origin at the centre of the pole. Thus the received flux from the point at the pole centre is zero.

Arthur