J.P.C. Smeets

Comparison of Position-Independent Contactless Energy Transfer Systems

This paper presents a comparison of position-independent contactless energy transfer systems by means of an inductive coupling, as a solution to overcome moving cables in emerging mechatronic applications with a linear moving load. A 2-D electromagnetic model of the contactless energy transfer system is derived and applied to six different topologies, which have either air-cored coils or a combination of salient or nonsalient magnetic cores. A parametric sweep is performed to obtain an optimal parameter set for each topology, suited for a power transfer of 1 kW with a position-independent mutual inductance between the primary and secondary coils. Comparison among the topologies shows that slotted topologies are less suited for a constant power transfer and that the geometry can be optimized for a mutual inductance variation below 3% along the linear movement.

Overview of Analytical Models for the Design of Linear and Planar Motors

In this paper, an overview of analytical techniques for the modeling of linear and planar permanent-magnet motors is given. These models can be used complementary to finite element analysis for fast evaluations of topologies, but they are indispensable for the design of magnetically levitated planar motors and other coreless multi-degrees of freedom motors, which are applied in (ultra) high-precision applications. The analytical methods describe the magnetic fields based on magnetic surface charges and Fourier series in 2-D and 3-D.

Optimal design of a pot core rotating transformer

This paper discusses the optimal design of a pot core rotating transformer to replace wires and slip rings in mechatronic systems by means of contactless energy transfer. Analytic models of the transformer are derived in the electromagnetic and thermal discipline. The models are compared with both 2D/3D FEM simulations and measurements. The analytical models are combined and used in a multi-objective sequential quadratic programming algorithm to find the minimal Pareto front in terms of volume and power loss for comparison of the adjacent and coaxial winding topologies. Finally, the optimization algorithm is used for the design of two prototype rotating transformers for a power transfer of 1kW peak, rotating at 4000 rpm. The prototypes are manufactured and tested in an experimental setup.

Modeling Framework for Contactless Energy Transfer Systems for Linear Actuators

This paper presents a semianalytical modeling framework to evaluate the performance of a contactless energy transfer system which consists of multiple primary windings and a linear moving secondary winding. The modeling framework combines steady-state and electromagnetic analyses and is able to deal with different winding configurations, consisting of combinations of nonmagnetic materials, iron plates, and slotted structures. In this paper, the modeling framework is used to compare the geometrical dimensions of the six different winding configurations under the condition of a constant magnetic coupling. The analysis shows that flat and thin primary windings and a flat and wide secondary winding are favorable for a constant magnetic coupling.

Three-Dimensional Analytical Modeling Technique of Electromagnetic Fields of Air-Cored Coils Surrounded by Different Ferromagnetic Boundaries

This paper presents a method for the calculation of the self- and mutual inductance of coils surrounded by air, positioned on top of a ferromagnetic plate and placed in a cavity inside a ferromagnetic plate. The magnetic fields around an array of air-cored coils are obtained by means of the three-dimensional magnetic vector potential using Fourier analysis. The current density distribution of a coil is modeled by four straight bars; three different configurations to position these bars against each other are presented as an alternative to model the round corners of a coil. An error of maximum 5% has been obtained in the analytically calculated flux density distribution compared to the values obtained from 3-D finite element simulations. Self- and mutual inductances are calculated for each current density description and compared with finite element simulations and measurements. A good agreement has been found for coils modeled by four overlapping or four trapezoidal bars.

Semianalytical Calculation of the Torque in a Linear Permanent-Magnet Motor With Finite Yoke Length

In this paper, a semianalytical model for the calculation of the torque produced by an iron-cored linear permanent-magnet motor is presented. The torque is calculated by means of the Maxwell stress tensor, which requires a description of the magnetic flux density distribution. The two-dimensional distribution is obtained from a semianalytical harmonic model, which accounts for the slotting and finite length of the iron yoke. An analytical expression for the thrust and normal force is obtained by evaluating the Maxwell stress tensor over a line through the air gap. For the torque calculation, the Maxwell stress tensor is numerically integrated along a contour that closely follows the structure of the yoke. The resulting torque and forces show good agreement with finite-element (FE) results.

Three-Dimensional Magnetic Field Modeling for Coupling Calculation Between Air-Cored Rectangular Coils

A semianalytical model is derived for the description of the three-dimensional magnetic field of an array of air-cored rectangular coils. The model describes the magnetic field with Fourier series and is obtained by solving the Maxwell equations using a combination of the magnetic vector and scalar potential. The model avoids the necessity of finite element analysis and allows three-dimensional analysis between air-cored rectangular coils in contactless energy transfer systems. As an example, the model is used to calculate the magnetic coupling between an array of primary and one secondary air-cored coil.

Contactless power transfer to a rotating disk

This paper discusses a power transfer system from the stationary to the rotating part of a device, by means of contactless energy transfer. A rotating transformer is proposed as a replacement for wires and slip rings. A pot core geometry is used for the rotating transformer and two different winding topologies are compared. The transformer is analyzed in the electromagnetic and thermal domain. An analytic model for each domain is derived. The validity of the analytical models is confirmed with both 2D and 3D FEM simulations and measurements. Two prototype rotating transformers are designed for the transfer of 1 kW peak, rotating at 6000 rpm. The prototypes are manufactured using commercially available pot cores and tested in an experimental setup.

Mode-Matching Technique Applied to Three-Dimensional Magnetic Field Modeling

A semianalytical model is derived for the description of the three-dimensional magnetic fields, generated by an array of air-cored rectangular coils above a ferromagnetic plate with cavities, or bounded slots, in the xy-plane. The magnetic fields are described with a double Fourier series and are obtained by solving the Maxwell equations using a combination of the magnetic vector and scalar potentials. Mode-matching of the double Fourier series is applied to obtain the description of the magnetic fields inside the cavities. Therefore, the mode-matching technique is extended for two dimensions. The semianalytical model is compared with three-dimensional finite element analysis and a good agreement has been found.

Design and control of a magnetically suspended ceiling actuator with infinite planar stroke

This paper presents the design and control of a magnetically suspended ceiling actuator which combines four iron-cored linear actuators and a checkerboard permanent magnet array for an infinite planar stroke. When the actuators are rotated with respect to the PM array, it is shown that the thrust and normal force produced by the three-phase linear actuators can be controlled by applying Parks transformation. The design of the iron-cored linear actuators is optimized for minimum losses when the translator inside the ceiling actuator and a payload are accelerated in the xy-plane. The optimization is performed using an analytical model is. Simulations of the optimized design with a 3D FE-model, show a maximum tracking error of 1 μm and rotations of 30 μrad when the translator is moved and controlled in 6 DOF.