Electromechanical Dynamics (Part 1).0049

Electromechanical Dynamics (Part 1).0049 - p and length f....

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Lumped Electromechanical Elements The calculation of terminal relations is now the same as described, except that in the permanent magnet (2.1.25) is used rather than (1.1.8). Example 2.1.3. The system shown in Fig. 2.1.2 is excited electrically by removing the N turns and placing a permanent magnet of length f in the magnetic circuit. Then the analysis of Example 2.1.1 is altered by the integration of (1.1.20) around the contour 1. If, in the section of lengthf, the material is characterized by (2.1.25), (a) of Example 2.1.1 is replaced by fB _ fB Hg + H 2 +o, (a) where B is the flux density in the magnet. Equation 1.1.21, however, again shows that B is the same in the magnet as it is in each of the air gaps. Hence B = oHM = oH, 2 (b) and (a) shows that B-- fB 0 B fBo (c) (•/lo)(g + X) +f ( Note from (a) that we can replace the permanent magnet with an equivalent current source I driving N turns, as shown in Fig. 2.1.2, but in which fB, NIi= and in the magnetic circuit there is a magnetic material of permeability
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Unformatted text preview: p and length f. This model allows us to compute forces of electrical origin for systems involving permanent magnets on the same basis as those excited by currents through electrical terminal pairs. 2.1.2 Generalized Capacitance To derive the terminal characteristics of lumped-parameter electric field systems we start with the quasi-static equations given in Table 1.2. The equations we need are (1.1.24) to (1.1.26) and (1.1.13): E - dl = 0, (1.1.24) SD.nda = p, dV, (1.1.25) D = eE + P, (1.1.13) fJ -n da = -p, dV. (1.1.26) We can use the differential forms of these equations alternatively, although the integral forms are more appropriate for the formalism of this section. It is essential to recognize that an ideal, lossless electric field system consists of a set of equipotential bodies with no conducting paths between them. A-PDF Split DEMO : Purchase from www.A-PDF.com to remove the watermark...
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