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The analysis of armature reaction field and winding inductance is extremely important for the design and control of electromagnetic motors. In this paper, a more accurate analytical model to predict the armature reaction field of an ironless brushless dc motor having either non-overlapping winding or overlapping winding is presented. First, for a non-overlapping winding analytical model, the field domain is divided into three subdomains, and for an overlapping winding analytical model, the field domain is divided into four subdomains. Second, the armature current model is established, and the field solution is obtained by solving Maxwell’s equations through the variable separation method and the use of adequate boundary and interface conditions. Third, the magnetic flied distribution in different subdomains calculated by the analytical method is compared with that calculated by the finite-element method (FEM). Last, the winding inductance is investigated as it is relatively small for an ironless motor, which introduces serious current/torque ripple. The accurate calculation of inductance is important for facilitating dynamic motion control. The results obtained by the analytical method and the FEM are compared and are in good agreement. A research prototype is developed, and experiments are carried out to verify the analytical results.

This paper presents an analytical magnetic field calculation for slotted brushless permanent-magnet (PM) machines equipped with surface inset magnets. The analytical expressions can be used to calculate both open-circuit and armature reaction field distributions. Although the expressions can be used for brushless PM machines with any magnetization pattern, the results of the open-circuit magnetic field are presented for three different magnetization patterns: radial, parallel, and Halbach. Different winding structures, such as overlapping, nonoverlapping with all teeth wound and nonoverlapping with alternate teeth wound, can be considered to compute the armature reaction field distribution. The analytical expressions can be used for the surface inset magnet structure with airspace between the magnets and the iron interpoles but they cannot be used in the case of brushless machines with surface mounted magnets. The calculations account for slotting and slot-opening effects via the subdomain technique. The analytical results for a four-pole, six-slot brushless PM machine with three magnetization patterns and nonoverlapping winding are presented and evaluated by comparing them with those obtained from the finite element method.

This paper presents an analytical solution for prediction of the armature reaction magnetic field in slotted surface mounted permanent magnet radial flux synchronous machines. This technique is used in the case of internal and external rotor radial-field machines. The magnetic field expressions are developed in both slots regions and magnetic airgap region leading to an exact calculation of the effects of slotting on the airgap magnetic quantities. Results from this analytical model are compared to corresponding finite element analyses. This analytical model is then used to estimate the self and mutual inductances.

A numerical computation of a squirrel cage induction machine parameters is presented using the finite element method (FEM). The effects of the main field and of the reaction field on the saturation are studied. The calculated parameters can be used in a field-oriented control system. >

A new way to couple the magnetic vector potential with the reduced or scalar potentials is discussed. The proposed method is based on a two-step solution procedure: first, a field due to the sources is computed considering the permeability of the magnetic regions as infinite, and then the true permeability of the regions is restored, and a reaction field is computed. Unlike the usual AV- Phi - Phi /sub r/ formulation, this new formulation can be employed even if the permeability of the regions described with A is much higher than that of the regions described with Phi or Phi /sub r/. >