Force calculation in electromagnetic devices

In this paper the authors show how the Maxwell stress tensor can be used, in practice, in order to determine local magnetic forces distribution in an electromagnetic system. An experimental set-up has been designed in view of comparing the theoretical results with the measurements

Passive Guidance Forces of Polarized Linear Motors Combined with Levitation Actuators Working in Partial Vacuum – Application to Swissmetro

Maglev (>400 km/h) refer to Maglev such as the Japanese JR-Maglev MLX, the German Transrapid and the USA Inductrack. The Swissmetro Project, presenting a unique aspect of Maglev, is designed to work under partial vacuum (400 km/h). The authors investigate the combination of the propulsion with the levitation. To minimize the heat due to the iron and copper losses, a polarized excitation is proposed with NdFeB PM for the magnetic way poles. This paper emphasis the determination of the passive guidance forces of the active magnetic way, based on 3D FEM analysis. The possibility, to use these passive forces to guide the vehicle, is presented. This paper describes the issues related to such technical choices

Temperature distribution of a ventricular assist device activated by a brushless DC motor

A theoretical analysis of temperature distribution on an artificial ventricular assist device is performed using three-dimensional finite element modelling. The model consists of 6000 solid elements representing all the ventricle components. In order to find out the maximum Joule's losses allowed for the motor design, the simulation is able to propose the temperature distribution in each ventricular component. The model is based on thermal-electrical analogy, allowing an equivalent thermal conductivity for composite material. Two modes of heat transfer (conduction and convection) are used in this model. Results show the temperature distribution in each component and particularly on the bag housing. Maximum temperature should not be over 41°C which is possible with a limit of 4 W motor Joule's losse

Reducing the cogging torque in brushless DC motors by using conformal mappings

We present an exact model for determining the cogging torque in a brushless DC (BLDC) motor. It is based on the conformal mapping (CM) method, by which the motor configuration is transformed to a configuration where the magnetic field can be determined. Then, by integrating the field over the stator surface, the cogging torque is determined. By varying some motor parameters, which is easy to do, an optimal configuration with the minimal cogging torque is obtained. We have confirmed the results by the finite-element method (FEM). The model produces results much faster than FEM alone

An exact formula for "tooth-to-tooth" permeance

We present a new, completely original exact method to determine the permeance between two opposing iron teeth. This configuration is important because it is often encountered in electrical machines and apparatus. The method is based on conformal mapping. The given "tooth-to-tooth" configuration is mapped into a simpler one, in which the same permeance can be analytically determined. We derive an explicit formula for this permeance, and confirm our results using the finite-element method. © 2005 IEEE

A square magnetic circuit analysis using Schwarz-Christoffel mapping

The paper presents an original method to determine the 2D magnetic field in a square magnetic circuit. To do it, the method of Schwarz-Christoffel mapping is used. This mapping is a special kind of the conformal mappings, applicable to polygonal 2D configurations. As the magnetic circuit is complicated, a numerical solution has to be applied. Knowing the magnetic field, the fluxes and inductances are determined. The results are verified using FEM commercial software. © 2006 IMACS