Magnetics Business & Technology - Winter 2017 - 8

FEATURE ARTICLE

Multi-physics Simulation of novel 3D Flux Machines
with Soft Magnetic Composite Cores
By Amed Khebir/ EM Works

Advances in magnetic material technology and constant push for
better performance have brought industry closer to widely accepting novel 3D flux electrical machine topologies. Soft magnetic composite materials offer greater design freedom to machine designers;
compared to laminated steels they have significantly lower eddy
current losses which open up possibilities for operation at higher
frequencies and smaller machine size [1]. On the other hand, 3D
flux machines are very difficult to model and simulate. Integration
of Solidworks and EMS by EMWorks, a powerful multi-physics simulation package, is an ideal solution for these problems.
Commercial and academic researchers are investing serious effort in development of configurations that only recently seemed
too exotic, such as transverse flux, axial flux, claw pole etc. A feature many of these machine types have in common is a complex
three-dimensional flux distribution, which makes their design and
electromagnetic modeling complicated. Analytical and experimental formulas are unable to resolve this simulation problem, due to
its sheer complexity and lack of experience with these machine
types. Standard 2D machine simulation suites are also inadequate;
furthermore, any change in the motor design usually requires dealing with limited CAD tools native to most of the simulation packages or importing externally created CAD files, which makes any
redesign or optimization extremely difficult.
EMWorks is an electromagnetic simulation company based in
Montreal, Canada. Its multi-physics simulation tool - EMS is fully
embedded in Solidworks, which is the most powerful platform for
handling complex spatial topologies. This symbiosis enables seamless redesign and electromechanical analysis of soft magnetic composite cores right inside Solidworks. EMS computes all the parameters relevant to a machine designer, such as core losses, winding
inductance, flux distribution, temperature rise, torque etc.

Transverse Flux Machines
In electrical vehicle, aerospace and other critical applications,
Transverse flux machines (TFMs) have received great attention in
the last few years for their high torque density (traditional electrical
machines are characterized by 0.24-0.8 kW/kg torque density, while
TFMs report 0.5 - 2 kW/kg) [2] and axial compactness [3]. The concept has convoluted spatial flux distribution and requires complex
manufacturing procedure. Although TFM idea has been around
for a couple of decades, its practical implementations has become
possible only recently, thanks to the advances in neodymium-ironboron and samarium-cobalt production [2].
TFM technology liberates machine design by placing the electrical and magnetic loading in different planes (Fig. 1-a). This way,
number of poles can be increased without reducing the magnetomotive force per pole, resulting in a higher thrust. End windings
that do not contribute to the torque production are eliminated,
leading to an enhanced efficiency.
Main disadvantage of the TFM technology is excessive winding
inductance that deteriorates the machine's performance in terms of
the power factor, core saturation and core loss [4]. Accurate evaluation of the TF machine's inductance requires detailed 3D model of
the structure and accurate material properties. Solidworks enables
high fidelity representation of the machine's parts, such as magnets, poles and slots, as well as their easy fine tuning; EMS in turn
takes care of the inductance computation at various frequencies
and nonlinear material characteristics. Furthermore, it also computes other winding parameters: AC resistance, mutual inductance
and losses.
Simplified analysis of TF machines is often conducted by neglecting its uncommonly pronounced magnetic flux leakage (partially due to the lower saturation levels in soft composites) and
can therefore predict unrealistic torque densities. EMS nonlinear

Figure 1. Transverse flux machine a) Elements: 1-armature winding, 2-stator pole shoes, 3-permanent magnets, 4-rotor back
iron, 5-flux, 6-current; b) Three dimensional TFM flux distribution calculated in EMWorks EMS

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