Simulation of Electric Machines with ANSYS · Simulation of Electric Machines with ANSYS Jens Otto...

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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…

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• 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

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Simulation Driven Product Development – Customer Workflow

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Marc Brück EM-motive a Bosch + Daimler Company

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Virtual Prototype: Simulation is Everywhere!

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• 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

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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

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Automatic Adaptive Meshing Example

- 8 -

Source ANSYS Inc.

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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

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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

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3D Vector Hysteresis Modeling

• Lamination support

• Optimization to minimize total error

of major & minor loop

• Non-zero initial condition support

footer 11

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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

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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

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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

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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.

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Torque

Currents

Periodic TDM is only solved for 1 period

Periodic TDM enhancement R18

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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

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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

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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

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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

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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

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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

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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Simulation of Electric Machines with ANSYS · Simulation of Electric Machines with ANSYS Jens Otto...

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