Magnetomotive Force


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magnetomotive force

[mag¦nēd·ō′mōd·iv ′fōrs]
(electromagnetism)
The work that would be required to carry a magnetic pole of unit strength once around a magnetic circuit. Abbreviated mmf.

Magnetomotive Force

 

a quantity that characterizes the magnetic action of an electric current. The magnetomotive force is introduced in calculations of magnetic circuits by analogy with the electromotive force in electric circuits.

The magnetomotive force F is equal to the circulation of the vector of magnetic field intensity H through a closed circuit L that encompasses the electric currents generated by the magnetic field:

(in the International System of Units). Here HI is the projection of H onto the direction of the element of the integration circuit d I and n is the number of conductors (coils) carrying a current Ii that are encompassed by the circuit. The unit of magnetomotive force is the ampere (or ampere-turn) in the International System of Units and the gilbert in the cgs system of units (symmetrical); 1 A = (4π/10) Gb ~ 1.2566 Gb.

References in periodicals archive ?
After completing the harmonic analysis of rotating magnetomotive force curves it was determined that the conditional amplitude of the fundamental harmonic of rotating magnetomotive force for the analysed motor was [F.sub.m11] = 0,914 [9], and the same amplitude generated by six-phase winding was [F.sub.m12] = 1,829.
Despite that windings of the investigated motors are identical only in part (windings of the same type, 2[p.sub.1] = 2[p.sub.2], [Z.sub.1] = [Z.sub.2]), the instantaneous spatial distributions of rotating magnetomotive forces generated by them are identical at any moment of time, as it can be seen from Fig.
Analysis of the considered short pitch coil winding indicates, that during one pole pitch the relative magnetomotive force [F.sub.1]([phi]) has the shape, shown in Fig.
Space harmonic spectrum of each winding magnetomotive force can be obtained on the base of Fourier series [12].
where [F.sub.v'(")m]--amplitude of v-th harmonic of rotating magnetomotive force; [F.sub.i]--conditional height of the i-th rectangle of the stair-shaped magnetomotive force halfperiod; [[beta].sub.i]--width of the i-th rectangle of the stair-shaped magnetomotive force half-period, expressed in electrical degrees; [[gamma].sub.i]--asymmetry of the i-th rectangle of the stair-shaped magnetomotive force half-period in respect of central axis of this half-period, expressed in electrical degrees; k-number of rectangles which constitute the stair-shaped magnetomotive force half-period; v--series number of odd space harmonic; v"--series number of even space harmonic.
here [F.sub.i] - the apparent size of the i-th rectangle of magnetomotive force; [[beta].sub.i] - the width of the i-th rectangle, expressed in electrical degrees of fundamental space harmonic; k - number of rectangles, which form the stairshape curve of half-period of magnetomotive force; v number of odd space harmonic.
1, a, the conditional changes of magnetomotive force in the slots of magnetic circuit are determined (Table 3).
Its magnetic circuit is composed of the magnetomotive force [F.sub.m], electromagnet magnetic core with the magnetic resistance [R.sub.mm] and gap with the magnetic resistance [R.sub.m0].
2, b, the amplitude value of rotating magnetomotive force of the v-th harmonic [F.sub.mv] is calculated using this analytical expression [4]:
Spatial distribution of rotating magnetomotive force in the defined moment of time was formed according to results presented in Table 2 (Fig.
Functions of instantaneous periodic rotating magnetomotive force of concentrated three-phase winding are square-shaped.
The reluctance force is produced by interaction of stator magnetomotive forces (mmf) and a reluctance variation produced by a toothed reactive part.