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© CADFEM 2017

Vibration and Acoustics for Electric Drive Development

Presenter: Jens Otto, CADFEM GmbH

Developer: Dr. Jürgen Wibbeler, Dr. Martin Hanke , CADFEM GmbH

1

4th CADFEM ANSYS Simulation Conference Ireland & UK

12th and 13th October, Engineers Ireland, Dublin

© CADFEM 2017

1. Business of CADFEM GmbH

2. Electrical Drives as Noise Sources

3. Concept of FEM-based Noise Computation

4. Computation of Magnetic Excitation Loads

5. Structural Dynamics and Noise using

Electric Drive Acoustics inside ANSYS

6. Summary and Additional Topics

Numerical Prediction of Motor Noise in a Continuous Speed Range 2

© CADFEM 2017

1. Business of CADFEM GmbH

CADFEM in Germany, Austria, Switzerland:

• Founded in 1985

• 2,300 customers

• 11 locations

• 220 employees

(≈ 130 of them technical experts)

BerlinHannover

Dortmund

Chemnitz

Stuttgart

Lausanne

Aadorf

Grafing Wien

InnsbruckZürichOtterfing

FrankfurtDarmstadt

Numerical Prediction of Motor Noise in a Continuous Speed Range 3

© CADFEM 2017

1. Business of CADFEM GmbH

CADFEM – Simulation is more than Software:

• ANSYS Elite Channel Partner

• PRODUCTS

Software und IT Solutions

• SERVICES

Advice, Support, Engineering

• KNOW-HOW

Transfer of Knowledge

Numerical Prediction of Motor Noise in a Continuous Speed Range 4

© CADFEM 2017

1. Business of CADFEM GmbH

CADFEM ANSYS Extensions:

Numerical Prediction of Motor Noise in a Continuous Speed Range 6

© CADFEM 2017

1. Business of CADFEM GmbH

2. Electrical Drives as Noise Sources

3. Concept of FEM-based Noise Computation

4. Computation of Magnetic Excitation Loads

5. Structural Dynamics and Noise using

Electric Drive Acoustics inside ANSYS

6. Summary and Additional Topics

Numerical Prediction of Motor Noise in a Continuous Speed Range 7

© CADFEM 2017

2. Electrical Drives as Noise Sources

E-mobility

Railway traction

Marine Propulsion

Energy Sector

Industrial Drives

Home Appliances

Universal Motors, …

Wikipedia

Wikipedia

Schottel

Numerical Prediction of Motor Noise in a Continuous Speed Range 8

© CADFEM 2017

2. Electrical Drives as Noise Sources

Origin of Noise by Electrical Drives:

Electric Drive Acoustics inside ANSYS

Magnetic Circuit

Gap forces

Fluidics

Cooling

Drive Side

Gearbox etc.

Reluctance, Geometry

Current Waveform,

Inverters

Magnetic Saturation

Courtesy of Elektromotorenwerk

Grünhain GmbH

Numerical Prediction of Motor Noise in a Continuous Speed Range 9

© CADFEM 2017

1. Business of CADFEM GmbH

2. Electrical Drives as Noise Sources

3. Concept of FEM-based Noise Computation

4. Computation of Magnetic Excitation Loads

5. Structural Dynamics and Noise using

Electric Drive Acoustics inside ANSYS

6. Summary and Additional Topics

Numerical Prediction of Motor Noise in a Continuous Speed Range 10

© CADFEM 2017

3. Concept of FEM-based Noise Computation

Positioning Noise Analysis (NVH) in a Motor Design Process:

Advanced MagneticsModeling

Maxwell 2D/3D

EfficientMotor Design Toolkit

Motor-CAD Mechanical,

CFDControl Logic, Software

System Validation

Lab

EmagThermal

Lab

NVH, Cooling

Design Analysis Operation

Numerical Prediction of Motor Noise in a Continuous Speed Range 11

© CADFEM 2017

3. Concept of FEM-based Noise Computation

Analysis Workflow:

Electro-

magnetic

Analysis

Harmonic

Vibration

AnalysisDFT

Oscillation,

ERP,

Waterfall PlotExcitation

Loads

External computation

of excitation loads

Numerical Prediction of Motor Noise in a Continuous Speed Range 12

© CADFEM 2017

3. Concept of FEM-based Noise Computation

Waterfall Diagram by Measurement:

• Equipment:

• Accelerometers

• Microphones

• Spectrum analyser

• Anechoic room

• Easy to record at controlled

run-up of a motor

Example traction drive (www.vem-group.com)

Numerical Prediction of Motor Noise in a Continuous Speed Range 13

© CADFEM 2017

3. Concept of FEM-based Noise Computation

Computational Effort for a Waterfall Diagram Produced by Simulation:

Example: 40 rotational speed points

30 spectral lines

= 1200 simulation points!

FEM-methods with minimized

computational effort required for

• electromagnetics

• structural dynamics

One simulation point per rotational

speed and spectral index!

Numerical Prediction of Motor Noise in a Continuous Speed Range 14

© CADFEM 2017

3. Concept of FEM-based Noise Computation

Equivalent Radiated Power (ERP):

• Obtained from structural velocity at

the vibrating surface

(surface normal component vn)

• Natural deviation from true radiation

by σ ≠ 1: Pacoustic = σ·PERP

• Advantage of ERP vs. air-born acoustics:

• No meshing of fluid space computationally less expensive

• Returns a fast figure of produced noise

• Indicates critical operating points efficient comparison of designs

AvcP dˆ2

1 2nERP

15Numerical Prediction of Motor Noise in a Continuous Speed Range

© CADFEM 2017

3. Concept of FEM-based Noise Computation

Utilization of Results:

f

n

ERP [dB]

Identify critical OPsGet vibration shapes

for critical OPs only

Analyse true radiation

by acoustic field

simulation

(optional;

by dedicated tools for

air-borne acoustics)

Numerical Prediction of Motor Noise in a Continuous Speed Range 16

© CADFEM 2017

1. Business of CADFEM GmbH

2. Electrical Drives as Noise Sources

3. Concept of FEM-based Noise Computation

4. Computation of Magnetic Excitation Loads

5. Structural Dynamics and Noise using

Electric Drive Acoustics inside ANSYS

6. Summary and Additional Topics

Numerical Prediction of Motor Noise in a Continuous Speed Range 17

© CADFEM 2017

4. Computation of Magnetic Excitation Loads

Excitation Loads at Stator (Time Domain):

• Goal:

Forces/moments acting at stator teeth(2D: Frad, Ftan, Mz; 3D: + Fz, Mrad, Mtan)

To be condensed to load centroids

Frad Ftan

Mz

Load

centroid

Maxwell 2D or 3D

Load as function of time:

Numerical Prediction of Motor Noise in a Continuous Speed Range 18

© CADFEM 2017

4. Computation of Magnetic Excitation Loads

Reducing Electromagnetic Simulation Runs:

• Loads vary continuously in characteristic

sections of the operating range.

A few OPs are sufficient to capture

load variation.

Reduce EM-Simulations to selected OPs

• Interpolate loads at intermediate OPs

later at structural simulation.

Internally done by E.D.A. inside ANSYS

Applicable to synchronous motors and

synchronous pulsed inverters

(required fi ~ n)

n2

n1

n3

Interpolation of

excitation loads

OP = operating point

Numerical Prediction of Motor Noise in a Continuous Speed Range 19

© CADFEM 2017

4. Computation of Magnetic Excitation Loads

Data Transfer to Structural Dynamics by Files:

• Export load sets for centroids of faces or face segments into csv-file:

(e.g. for 2D load sets: Time, Frad1, Ftan1, Mz1, Frad2, Ftan2, Mz2, …)

Numerical Prediction of Motor Noise in a Continuous Speed Range 20

© CADFEM 2017

1. Business of CADFEM GmbH

2. Electrical Drives as Noise Sources

3. Concept of FEM-based Noise Computation

4. Computation of Magnetic Excitation Loads

5. Structural Dynamics and Noise using

Electric Drive Acoustics inside ANSYS

6. Summary and Additional Topics

Numerical Prediction of Motor Noise in a Continuous Speed Range 21

© CADFEM 2017

5. Structural Dynamics and Noise Using Electric Drive Acoustics inside ANSYS

Workbench Project: Harmonic Analysis Based on Mode Superposition (MSUP)

• Eigenmodes and Eigenfrequencies

as intermediate result

• Faster than full harmonic analysis

• Excitations as input to harmonic analysis

Mode 1 Mode 3 Mode 6

610 Hz 1456 Hz 2654 Hz

Excitations

Modal Analysis Harmon. Analysis

ANSYS Project Structure:

Numerical Prediction of Motor Noise in a Continuous Speed Range 22

© CADFEM 2017

5. Structural Dynamics and Noise Using Electric Drive Acoustics inside ANSYS

Speed-up at ERP-computation Based on MSUP Harmonic Analysis:

Full Harmonic Analysis

Vibration of structural nodes

ERPComputationally

expensive!

Method used by

E.D.A. inside

ANSYS

MSUP Harmonic

Analysis

Vibration of structural nodes

Complex modal displace-

ments ("modal coordinates")

ERP

Expansion Pass

ERP

Time and memory

saving!

AvcP dˆ2

1 2nERP

Numerical Prediction of Motor Noise in a Continuous Speed Range 23

© CADFEM 2017

5. Structural Dynamics and Noise Using Electric Drive Acoustics inside ANSYS

Electric Drive Acoustics

inside ANSYS:

• ACT-based Extension

for ANSYS Mechanical

• Appears as a toolbar

in the GUI

Numerical Prediction of Motor Noise in a Continuous Speed Range 24

© CADFEM 2017

5. Structural Dynamics and Noise Using Electric Drive Acoustics inside ANSYS

Support of Load Import and Application:

• Text based import

interface,

flexible formats

• DFT at import

• Graphical check

• Load application

always

at Remote Points

(= load centroides)

Import preview

Load file table

Numerical Prediction of Motor Noise in a Continuous Speed Range 25

Remote Points

attached to faces

Excitation

loads

© CADFEM 2017

5. Structural Dynamics and Noise Using Electric Drive Acoustics inside ANSYS

Treatment of Non-skewed and Skewed Motors:

Non-skewed Skewed

Single point per stator tooth Axial discretization of loads

Numerical Prediction of Motor Noise in a Continuous Speed Range 26

© CADFEM 2017

5. Structural Dynamics and Noise Using Electric Drive Acoustics inside ANSYS

Support of Solution and ERP-postprocessing:

Extraction of vibration

shape at selected OP

Definition of sweep parameters

ERP-spectrum at

selected speed point

ERP-waterfall diagram

across speed range

Numerical Prediction of Motor Noise in a Continuous Speed Range 27

© CADFEM 2017

1. Business of CADFEM GmbH

2. Electrical Drives as Noise Sources

3. Concept of FEM-based Noise Computation

4. Computation of Magnetic Excitation Loads

5. Structural Dynamics and Noise using

Electric Drive Acoustics inside ANSYS

6. Summary and Additional Topics

Numerical Prediction of Motor Noise in a Continuous Speed Range 28

© CADFEM 2017

6. Summary and Additional Topics

Summary:

• ANSYS-based tool for efficient assessment of noise induced by magnetics

• ERP Waterfall diagram

• Continuous workflow with easy-to-use functions

• First release in July 2017

www.cadfem.de

Numerical Prediction of Motor Noise in a Continuous Speed Range 29

© CADFEM 2017

6. Summary and Additional Topics

Selection of Additional Topics:

Lamination and coil modeling

r0

r8

0.001

0.01

0.1

1

0 4 8 12 16 20 24 28 32 36 40 44 48

r0

r4

r8

r12

Circular force pattern analysis

Induction motors,

Inverters

Connection to parametrics

and optimization

Numerical Prediction of Motor Noise in a Continuous Speed Range 30

© CADFEM 2017 31

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