Magnetic field analysis of an ironless brushless DC machine

Abstract

This paper presents an analytical solution for the magnetic field inside an unconventional ironless brushless (ILBL) dc motor design. We discuss the unique characteristics of the design, which adopts an "inside-out" construction with an internal ironless stator. With the intention of obtaining an analytical solution for the magnetic field, we propose a model based on a magnetic pole concept for representing the magnetic circuit. The magnetic field inside the motor, which has no iron for guiding magnetic flux paths, is obtained by solving Laplace's equation for magnetic scalar potential. We present both analytical and numerical solutions for the magnetic field and compare them with measured results of a 20-pole prototype IL design to show the validity of the model. The IL design is simple, easy to manufacture and, as indicated by the results, has an optimum number of magnets, for which its performance becomes maximum.

Design and Performance Analysis of Coreless Axial-Flux Permanent-Magnet Generator for Small Wind Turbines

“…Assuming that at the axial middle of the stator the flux distribution generated by the armature coils with current excitations assumes a 'conical' shape, as has been reported in the literature [1,5]. Therefore, the flux density is presumed to be constant over the center of the circular coil and to decrease linearly across the coil.…”

“…As a result of this lower structural load and lack of iron core, the coreless configuration eliminates all ferromagnetic material including the steel laminations that would otherwise be needed in the stator, and so does not incur any associated eddy current or hysteresis core losses. By eliminating the core losses, a coreless-stator AFPMG machine can operate at a higher efficiency than a conventional machine [3][4][5].…”

Approaches to prove the rotor of the permanent magnet machine must be outside in order to improve the energy conversion process

“…Consequently, it is expected that the output torque, efficiency and performance all are different from each other. From these facts, the rotor of the permanent magnet machine must to be located in the right location that enables the use the most suitable design [9]. Some argue that the external location of the static parts in the internal rotor permanent magnet machines are safe for users and a better for ventilation, also they argue that the external location of the static parts enable the machine to be used in many applications such as these require integrating the electrical machine in a flywheel.…”

Simulation of Outer Rotor Permanent Magnet Brushless DC Motor Using Finite Element Method for Torque Improvement

“…For a given outer radius, an outer rotor motor has a much larger air gap radius than that of an inner rotor motor. As a result, higher torque is achievable, provided the ohmic losses of the stator windings can be dissipated [5][6][7].…”