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© CADFEM 2017
Simulation of Electric Machines with ANSYS
Jens Otto – CADFEM GmbH
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© CADFEM 2017
Why Simulation with ANSYS ? Challenges for electric machines…
- 2 -
• Electromagnetic Design:
• Rated power/ Power-Volume-Ratio
• Material consumption
• Losses/Efficiency
• Torque ripple
• Circuit interaction
• Structural Design:
• Housing integrity
• Active steel integrity
• Winding-end design
• Cooling Design
• Air/Fluid flow
• Coupled Analyses:
• Temperature prediction
• Vibroacoustics
© CADFEM 2017
Simulation Driven Product Development – Customer Workflow
3
Marc Brück EM-motive a Bosch + Daimler Company
© CADFEM 2017
Virtual Prototype: Simulation is Everywhere!
4
• Electromagnetic is just
one aspect of design
• EADT also part of
Workbench environment
• Thermal
• Fluid-flow
• Structural
• Coupled Simulation
© CADFEM 2017
Electromagnetic FEM Solution in ANYS Maxwell
- 5 -
Maxwell:
• Static
• Time-Dependent
• Time domain (Transient)
• Frequency domain (Harmonic)
• Motion (Linear, Rotational)
• Advanced physics capability
• 2D; 2.5D; 3D
• Materials
• Circuit coupling
Source: CADFEM
© CADFEM 2017
Maxwell’s Approach: Finite Element Method
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• Translate differential equation to
algebraic equations
• Split one “big” task into a finite
number of “simple” subtasks
• Discretize space by
tetrahedrons/triangles
• Solution only at element’s nodes
• Quantities are interpolated between
nodes
Solution
computed
on nodes
Source:CADFEM
© CADFEM 2017
Automatic Adaptive Meshing
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• Generate efficient mesh without
expert mesh know-how
• Find a compromise accuracy vs
simulation time
• User defined convergence criteria
• Global energy error (default)
• Torque
• Force
• Inductance
• Adaptive meshing available
for all non-transient solvers
Calculate local
Solution error
Generate Initial
Mesh
Solve fields using the
Finite Element Method
End criteria
reached ?
Refine Mesh
Calculate Outputs
(Force, Inductance, etc.)
no
yes
Start
© CADFEM 2017
Automatic Adaptive Meshing Example
- 8 -
Source ANSYS Inc.
© CADFEM 2017
Mesh Operations
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• Can be combined with adaptive
approach
• Fewer iterations
• Faster solution times
• Mesh refinement for transient
simulations
• Manual mesh refinement
• Import mesh from static/harmonic
Source CADFEM
© CADFEM 2017
True Motion in Electromagnetic Simulation
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• User friendly configuration
• Velocity dependent effects
• Eddy currents (effect on field)
• PMs
• Squirrel cage
• Conducting slot wedges/
mechanical parts
• External particles
© CADFEM 2017
3D Vector Hysteresis Modeling
• Lamination support
• Optimization to minimize total error
of major & minor loop
• Non-zero initial condition support
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© CADFEM 2017
Material properties
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• Nonlinear and/or anisotropic permeability
• Anisotropic conductivity
• Core loss model
• Steinmetz approach
• electrical steel
• power ferrite
• Solid or lamination model
• Scaling of B-H curve
• Temperature dependent
© CADFEM 2017
User Friendly Extraction of Steinmetz Coefficients
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• Select “Electrical Steel” or “Power Ferrite”
• Select extraction method
• Core loss versus frequency
• Core loss at one frequency
• Iron’s conductivity needed
• Lamination thickness needed
• Input datasheet data from supplier
• Manual
• csv, txt import
• Sheet scan
• Automatic calculation of coefficients
• Automatic update in material properties
© CADFEM 2017
Simulation Dimensionality
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• 2D Simulation
• Planar B-field
• General machine sizing
• 2.5D for skewing approximation
• Stepwise approximation
• 3D
• Full flexibility
• Detailed eddy current paths
• End effects (Stray fields)
• Non planar flux
© CADFEM 2017
Since R17: Time Decomposition Method
• HPC-Method for transient magnetic
designs
• Simultaneous calculation of k time
steps
• N-Tasks containing k-time steps each
• N-Tasks can be distibuted in DMP
mode
… T1 Tk
k –Time Steps
n – Parallel
Distribued Tasks
Matrix Size
X k
T1
T2
T3
T(k-2)
T(k-1)
T(k)
Source: ANSYS Inc.
© CADFEM 2017
Torque
Currents
Periodic TDM is only solved for 1 period
Periodic TDM enhancement R18
© CADFEM 2017
Periodic TDM enhancement R18: Example
• Synchronous generator
• 350,000 elements, 2nd order
elements
• Eddy current in bars
• 3 Simulation cases:
• 8 cores HPC (no-TDM) over 10
electrical periods
• 112 cores HPC (TDM general
transient) over 10 electrical periods
• 112 cores HPC (TDM periodic) solving
just 1 electrical period
20ms
# of cores HPC Method Used Simulation time Speed up
8 No-TDM 151h45min -
112 General Transient
TDM 22h53min 6.6
112 Periodic
TDM 7h33 20
© CADFEM 2017
Coupled Circuit-Motor Analysis in ANSYS Maxwell
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• Maxwell includes circuit editor
• Sources
• Passive elements (R-L-C)
• Diodes
• Switches
• Couple EM-field to Circuit
• Dedicated elements
• Winding
Source CADFEM
© CADFEM 2017
System Analysis of Electric Machines
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• Why SIMPLORER?
• Detailed switch models
(Semiconductor)
• Control Loops
• Terminal coupling to other domains
• System simulation using ANSYS
Simplorer
• Embedded motor model
• PE-Circuit
• Control
• Co-simulation with
Simulink and Maxwell
• Other Domains
• Mechanical
• Thermal
Source CADFEM
© CADFEM 2017
Simplorer: Electric Powertrain – System with Thermal Simulation
Heat-Sink + Fan Model Extraction from CFD
Power Transistor Electrothermal
Characterisation
Motor Magnetic FEM Co-simulation
© CADFEM 2017
Virtual Prototype: Simulation is Everywhere!
21
• Electromagnetic is just
one aspect of design
• EADT also part of
Workbench environment
• Thermal
• Fluid-flow
• Structural
• Coupled Simulation
Mechanical Thermal / Stress
CFD Fluid Flow /
Thermal
© CADFEM 2017
Stress & Fatigue Life
• Centrifugal and magnetic forces
• Nonlinear contact between magnet
and steel
• Definition of rotor shape according to
• Deformation
• Stresses
• Fatigue life
© CADFEM 2017
Thermal – Efficient Fluid Models
• Components often cooled
by fluid flow
• Fluid flow by detailed CFD requires
computing power
• ANSYS heat pipe model with semi-
analytical approach
• Objective: Reduce simulation time
maintaining global result accuracy
• Restriction: Exact knowledge of fluid
flow not of interest
Oil flow channels
Axial air flow
Axial T-
gradient
Source: CADFEM GmbH
© CADFEM 2017
Application Case: Thermal Integrity Simulation
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• Losses from EM-Simulation used as
realistic loads
• Thermal analysis in Mechanical
• Thermal analysis in Fluent
• Automatic Mesh interpolation
• 2D-3D interpolation capability
• Energy preserving
© CADFEM 2017
Dynamic Temperature Dependent Coupled Demagnetization
• Maxwell Transient
• 3A current pulse
• First thermal iteration on original
curve
• Second iteration on lower level
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1st thermal
iteration
2nd thermal
iteration
© CADFEM 2017
Coupling: Magnetostriction Analyses
Applications:
• Vibration and noise
analysis
• Transformers
• Electrical machines
• Actuators
• Control devices
• Sensors and transducers
• Smart materials
Magnetic characteristic changes under mechanical stress
Physical dimension changes due to magnetic field
Inverse Magnetostriction
Magnetostriction
Electro-magnetic
Solution
Displacement Vector +
Strain & Stress Tensor
Magnetic Force +
Magnetostriction Force
Mechanical
Structure Solution
© CADFEM 2017
EM Force + Magnetostriction
EM Force
Strain = f(H) • Force Calculation on a Tooth Tip • Suitable for NVH simulation
Example: Magnetostriction Analyses effecting forces of machines
© CADFEM 2017
Application Case: Vibroacoustic Calculation
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© CADFEM 2017
Parametric Simulation
• What is the benefit of a single
simulation?
• Variation gives most understanding
• Geometric shape
• Material
• Current
• Windings
• Circuits
• Controller
• …
• DoE, Optimization,
Robust Design
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Geometry
± 0.1-10%
Material
± 5-10%
Boundary Conditions
± 1-20%
Result
± ??%
Manufacturing
± 5- 30%
Loads, Signals
± 0.1-50%
© CADFEM 2017
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© CADFEM 2017
Thank you!
Questions ?
(please use the chat)
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© CADFEM 2017
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