What is the difference between an axial flux motor and a radial flux motor?

An axial flux motor has a structure where the magnetic flux flows parallel to the axis of rotation, enabling a thin profile and high torque density. In a radial flux motor, the magnetic flux flows radially. The axial type is ideal for in-wheel EV motors and drone propulsion.

How is torque calculated for an axial flux motor?

It is calculated by performing a surface integral over the air gap using the Maxwell stress tensor. The fundamental formula is T = ∫r×(σ·n)dA, where σ is the Maxwell stress tensor and n is the normal vector to the air gap surface.

What software is commonly used for electromagnetic field analysis of axial flux motors?

JMAG-Designer, which includes built-in templates for axial flux types, is widely used in Japanese motor design. Ansys Maxwell excels at 3D transient analysis, while COMSOL Multiphysics is adept at multiphysics coupling.

Why is 3D analysis essential for axial flux motors?

Because the magnetic flux in an axial flux motor flows axially, a 2D cross-sectional analysis (as often used for radial types) cannot accurately represent the magnetic circuit. 3D analysis is indispensable for evaluating the radial distribution of air gap flux density and end effects.

Electromagnetic Field Simulation of Axial Flux Motors

Category: Electromagnetic Field Analysis / Motor Design | Updated 2026-04-11

Axial flux motor electromagnetic simulation showing flux density distribution in airgap and stator core — Axial Flux Motor Magnetic Flux Density Distribution Simulation ― Contours of radial and circumferential magnetic flux density on the air gap surface

Theory and Physics

Axial-Type Structure and Magnetic Flux Path

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What's the difference between an axial flux motor and a regular radial type? I've heard the name but can't picture it...

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It's a thin motor structure where magnetic flux flows in the direction of the rotation axis. It offers high torque density and is lightweight. It's a new structure gaining attention for EV in-wheel motors and drone propulsion.

Governing Equations

$$ T = \frac{\pi}{4}(R_o^2-R_i^2)B_g A_s $$

$$ P = T\omega $$

Discretization Methods

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How do you actually solve these equations on a computer?

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We use spatial discretization by the Finite Element Method (FEM). We assemble the element stiffness matrices and construct the global stiffness equation.

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We transform it into the weak form (variational form) and use formulation by the Galerkin method using test functions and shape functions. The choice of element type (low-order elements vs. higher-order elements, full integration vs. reduced integration) is directly linked to the trade-off between solution accuracy and computational cost.

Matrix Solution Algorithms

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What exactly are matrix solution algorithms?

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We solve the simultaneous equations using direct methods (LU decomposition, Cholesky decomposition) or iterative methods (CG method, GMRES method). Preconditioned iterative methods are effective for large-scale problems.

Solver	Classification	Memory Usage	Applicable Scale
LU Decomposition	Direct Method	O(n²)	Small to Medium Scale
Cholesky Decomposition	Direct Method (Symmetric Positive Definite)	O(n²)	Small to Medium Scale
PCG Method	Iterative Method	O(n)	Large Scale
GMRES Method	Iterative Method	O(n·m)	Large Scale / Non-Symmetric
AMG Preconditioner	Preprocessing	O(n)	Very Large Scale

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So, if you cut corners on the finite element method part, you'll pay for it later. I'll keep that in mind!

Implementation in Commercial Tools

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So, what software can be used for axial flux motors?

Tool Name	Developer/Current	Main File Format
JMAG-Designer	JSOL Corporation	.jmag, .jproj
Ansys Maxwell	Ansys Inc.	.aedt, .maxwell
COMSOL Multiphysics	COMSOL AB	.mph
Ansys HFSS	Ansys Inc.	.aedt, .hfss

Vendor History and Product Integration Background

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Is the origin of each software somewhat dramatic?

JMAG-Designer

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What exactly is JMAG?

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Developed by Japan's JSOL Corporation. An electromagnetic field analysis tool specialized for electrical equipment design.

Current Affiliation: JSOL Corporation

Ansys Maxwell

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Tell me about "Ansys Maxwell"!