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Flux – Motor Design Tool
A key success factor for our
MACCON customised motor
designs
15.10.2014
1
Agenda
First section of the presentation:
-Showing 3 challenging projects which were helped to success by the
unique features which Flux offers
Second section of the presentation:
- Calculation of magnetic losses for an axially segmented magnet
arrangements, using a 2D model
- Setting up a 3D model for a segmented magnetic arrangement
- Discussion of the results of the 3D modelling with different
segmentation lengths
- Derivation/evaluation of an substitute 2D model using an substitute
conductivity
General remark: The pictures used in this presentation were taken from
science projects and are not assigned for publications.
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First example:
An optimization problem
Problem description:
An optical system for a space application should be protected by a
screen against sunlight. The customer requests control electronics
being as simple as possible. He intends to control each a transistor
for the movement towards and a transistor in the reverse direction.
For redundancy reasons a second pair of transistors and a
redundant coil system should be used.
In addition, the customer does not want to use a closed control with
position feedback for this system. Since the folding arm has a large
inertia together with the flap, the motion must absolutely run without
jolting to avoid disturbances on the satellite.
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Example for an optimization problem
Replacement design for the overview of the mechanical design
of the flap unit:
Design of the drive motor
and winding:
30mm
60mm
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Example for an optimization problem
Solution of the problem by means of Flux and GOT-It as well as
Matlab-Simulink-coupling:
GOT-It
Matlab- Simulink
Flux-Skewed
Coil Main
Final result of design:
The different current profiles have the same
characteristic; they are only differing in the amplitude
Coil Redundant
Damping
Coil
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Second example:
An acoustic noise optimization
Problem description:
In this project a special traction motor has to be designed for a driving
application in the sea water. In addition to the specified driving loads, the
acoustic noise excitation has to be minimized to assure that disturbance of
marine life is reduced as much as possible.
Therefore, the acoustic noise radiation of the surrounding mechanics which
is transmitted from the electromagnetic tooth forces has to be minimized.
This can be realized by having as much as possible difference between
the frequencies of the electromagnetic induced forces on the stator tooth
and the mechanical Eigen frequencies of the surrounding mechanics.
To achieve this optimization, the forces on the stator tooth have to be
analyzed by a Discrete Fourier transformation gained from the gap flux
distribution. These results have to be compared to the mechanic modal
analysis.
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Second example:
An acoustic noise optimization
On the one hand the frequencies spectrum of the excitation forces can
be determined by Discrete Fourier transformation gained from the gap
flux distribution. On the other hand, with the help of the mechanical
mode analysis, it can be analyzed which of the wave forms are
interacting with mechanics. By influencing the mechanical structure
with regard to the excitation wave forms it can be obtained that the
excitation level can be significantly decreased.
Mechanical structure
Result of air gap flux densities analysis
which is used for the Discrete Fourier
transformation along an air gap path:
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Second example:
An acoustic noise optimization
DFT calculation of
magnetic air gap flux
density:
Circumferential nodes
Frequency
Calculation of magnetic
force density:
Mode
B [T]
11
660
1.1939
33
1980
0.1624
13
661
0.1439
35
654
0.0908
37
664
11
77
Circumferential
nodes
Frequency
210788.19
44
2640
77156.96
24
1321
68367.49
0.0679
46
1314
43120.39
4905
0.0573
48
1324
32240.10
4621
0.0512
22
5565
27199.68
59
659
0.0440
3961
26991.00
99
5941
0.0400
66
1319
20912.25
61
665
0.0362
70
1325
17214.66
83
654
0.0304
72
1314
85
665
0.0291
94
14436.02
672
0.0278
1325
13828.27
7
96
654
0.0270
1332
13226.13
107
18
671
0.0244
16
1322
11224.69
109
662
0.0235
44
2638
9309.24
5
131
652
0.0217
46
2641
9301.43
55
3298
0.0196
20
1319
9301.43
121
7262
0.0195
66
3958
9217.97
133
670
0.0183
28
1327
7804.56
17
667
0.0164
20
2687
7521.58
155
658
0.0163
88
5281
7310.66
9
2027
0.0158
42
1320
7232.74
31
660
0.0152
30
1304
7032.02
22
σ~B^2/µ0
1
Frequency
[Hz]
561.1
2
3
4
1357.1
1359.7
1546.2
5
1746.5
6
1753.2
7
8
9
2173.6
2175.8
2226.5
10
2228.5
11
2345.2
12
2369.1
13
2551.2
14
2770.5
σ [N/m²]
1320
19
644
0.0148
52
1338
5991.21
157
676
0.0131
68
2634
5866.43
41
678
0.0126
66
3960
5248.62
179
649
0.0112
48
1315
5198.15
29
656
0.0110
40
1316
4906.64
181
675
0.0089
4
1316
4386.28
70
2644
4386.28
15.10.2014
Results of the
mechanical modal analysis:
Description
Axial vibration of rotor and
bearing shield
Vertical vibration of rotor
Horizontal vibration of rotor
Axial vibration of stator and
housing
Vertical 2 node vibration of
stator and housing
Horizontal 2 node vibration of
stator and housing
Yawing vibration of rotor
Tilt vibration of rotor
Tilting plus 2 node vibration of
stator and housing
Yawing plus 2 node vibration of
stator and housing
Circumferential 4 node vibration
of stator and housing (1)
Circumferential 4 node vibration
of stator and housing (2)
Torsional vibration of stator and
housing on connectors side
Vibration of connectors
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Second example:
An acoustic noise optimization
Only at a frequency of approx. 1.3 kHz, one radial force with 4 nodes
at the circumference is computed. This magnetic force calculation point
has a frequency distance of more than 1 kHz to the corresponding
natural modes of vibration and - in addition to this - a relatively small
force amplitude of nearly 2% compared to the fundamental radial force
density wave at f = 1320 Hz with 22 nodes at the circumference.
Mode 12
Mode 11
Circumferential
nodes
4
Frequency
1316
23.10.201415.10.2014
σ [N/m²]
4386.28
9
Second example:
An acoustic noise optimization
Example for 4 node oscillation:
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Second example:
Multiphysics coupling between Flux and
vibro-acoustic codes
Multiphysics
First target: Coupling between Flux and vibro-acoustic codes:
LMS Virtual Lab, NASTRAN, …
Currently working in the framework of a collaborative project
>> With Renault, UTC, Vibratech, Adetel
Command Electromagnetic forces
Stator vibrations
Noise
Future Developments – V. Leconte
2012 Flux Conference - Rome, Italy, October 17-18, 2012
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Third example:
System simulation with help of
Flux / Portunus
Problem description:
In this project a special traction motor has to be designed for operating in
a relatively high speed range (~3500 rpm) by a relatively low driving
voltage (~300 VDC). Due to constructive restrictions it was not possible to
choose a rotor design with embedded magnets.
Consequently, the inductances of the motor could only be designed in a
certain range. In addition to
that, the power factor has to
be designed in a certain range
in order to assure that the supply
battery is only in a certain load range.
Due to this requirements it is very
important to realize the possibility
to set up a very good system simulation.
Furthermore the thermal of the power electronics has to analyzed.
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Third example:
System simulation with help of
Flux / Portunus
Structure of the system simulation:
Park-TransFormation-block
with controlling the id
and iq-current
Inverter-model
with batterysupply
Motor-model with motor parameters
evaluated with Flux
Id and Iq-current / voltage reference values
for different filed weakening situations
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Third example:
System simulation with help of
Flux / Portunus
Results of the simulation:
Current
ripples in the
motor phase
and current in
the battery
Result balance active power, apparent power and
reactive power current-balance
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BREAK
End of first section
second section will
follow in the
afternoon
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Modelling with Flux in 3D for transient
application /
Derivation of a replacement method in 2D
Working with Flux in 3D:
- Some considerations about eddy currents
- Setting up a 3D model for a SPM-motor in order to compute magnet
losses for different axial segmentation lengths
- Comparison of the 3D model with a 2D computation model
- Derivation of a 3D model compared to computation of magnetic losses
for different magnet segmentation length with only 2D computation by the
help of a conductivity replacement factor
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Reasons for eddy current inductions
Generation of eddy current losses in the magnets:
Slotting of the stator
Pulsation of the magnetic flux when current is
supplied an electric machine with distributed
winding (single tooth windings are muc more
critical)
Varying air gap length
Reduction of the air gap induction under slot openings
Harmonics of the stator field in the air gap
Spatially fixed inductive dips (pulsation of the air gap
field) upon rotation of the rotor
Do not move synchronously with the rotor
Eddy currents and consequently eddy current losses in the magnets
Torque variations
Current supply of the stator by an inverter
By optimizing the inverter influence of harmonics can minimize optimized to
sinusoidal current supply
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Modelling with Flux for a 2D of transient
application
Modelling of the magnet losses in 2D for a magnet segmentation
in radial direction:
High-value resistors
 to assure that the total current in each magnet segment
is equal to zero
Mesh structure
for the surface magnet
with an optimized FEM mesh
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Eddy current distribution Flux in 3D of
transient application
Result of the eddy-current computation
in the magnet or a 2D model:
Slotting induced eddy-current distribution
for current supply
Slotting induced eddy-current distribution
without current supply
High eddy current densities below the slots
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Modelling with Flux for a 2D of transient
application
Results of the modelling of the magnet losses in 2D for a magnet
segmentation in radial direction and compared to an segmentation in axial
direction:
Increasing up the maximum speed up
to 12000 rpm
Exponentially increase of the eddy
current losses
l /  n  25mm / 13,15mm  1,9
9 magnet segments in radial direction
Very effective possibility of reducing
Decreasing the losses by 44%
8 magnet segments in radial direction
Stator outer
diameter: 235 mm
Active motor length:
30 mm
Number of slots = 36
Poles = 4
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Additional loss reduction of 33%
Overall loss reduction by axial and radial
segmentation 63%
20
Analytic model for the rough estimation of
the influence of the magnet segmentation
Skin-effect causes elliptically eddy
current paths with high eddy
current densities in the edge
areas
Eddy-currents in
the monolithic
magnet
Total losses will be changed in the ratio:
SPEED's Electric Machines,
Page 2.208
For the case that L is approximately
pole-pitch τ:
23.10.2014
equal to the
Radial segmentation
is more effective
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Modelling with Flux in 3D for a transient
application
Modelling in 3D of the magnet losses for different lengths of
magnet segmentation:
Mesh for the Magnets
are transformed
in z- direction by block
mesh elements
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Modelling with Flux in 3D for a transient
application
Movie to show the preparation and results for the 3D model:
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Modelling with Flux in 3D of transient
application
Eddy current density distribution under load for different segmentation
length:
3 times higher eddy
current loss density
5 mm length of the magnet
segments
15 mm length of the magnet
segments
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Modelling with Flux in 3D of transient
application
Eddy current density distribution for no load case compared to the case
under load:
Eddy current densities
for load case
are doubled
Eddy current density for the no load case
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Eddy current density
for the load case
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Modelling with Flux in 3D of transient
application
Eddy current penetration density for no load case compared to the case
under load:
No load case
Load case
- Depth of penetration (decreasing to 1/e-times)
- Depth of penetration (decreasing to 1/e-times)
is around 2.5 mm
is around 4 mm
- At 2.5 mm: Eddy current densities of 0.75*106 A/m2
- At 2.5 mm: Eddy current densities of 0.4*106 A/m2
- More volume of eddy currents is penetrated
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Modelling with Flux in 3D of transient
application
Comparison of the case with load and without load:
Eddy currents penetrate by very complex paths the magnetic volume
High tangential components of the eddy currents
Corner regions are not penetrated by the elliptical eddy current paths
Maximum eddy current densities are double for the load case compared to case without load
For the load case the penetration depth of the eddy currents is ~40% more
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Modelling with Flux in 3D of transient
application
Derivation of an substitute 2D model using an substitute conductivity:
N.Boules, W.-R.Canders und H.Weh.
Analytische Bestimmung
des Nutungseinflusses auf die Feldverteilung und
Wirbelstromverluste in dauermagneterregten
Synchronmaschinen. Archiv für Elektrotechnik 62
283-293. Springer-Verlag 1980. Braunschweig.
Definition of the replacement conductivity:
With : Factor for the finite extension of the magnets
in the axial direction
With : Finite extent in the azimuthal direction (~0,9)
And with
: conductivity of NdFeB-magnet
material
Kb-factor as
function
of magnet length
divided by
pole pitch
15.10.2014
Due to the segmentation of the magnets an
increase of the conductivity of the magnets is
occurring
The increase of the conductivity can be derived
by a correction factor
 *  kb k i 
   r  j i 
 * ( r  1) 2   i2
kb 

ki 
r  i
1  jr 
tanh(ˆl / 2)
1  jr
( ˆl / 2)

ˆ 
1  jr 
n
Example for this special motor design
kb  0,64
l /  n  25mm / 13,15mm  1,9
Reduction of the conductivity of 36%
28
Modelling with Flux in 3D of transient
application
Comparison of the 3D computation of the eddy current losses compared
to 2D computation with the help of the evaluated kb-factor:
29
Below a magnet segmentation length
of 20 mm the values of the 2D models
are higher.
But the deviation of the two approaches
is in the maximum range of 10%.
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Modelling with Flux in 3D of transient
application
Comparison of the 3D computation of the eddy current losses compared
to 2D computation with the help of the evaluated kb-factor:
2D- model
3D- model
30
The deviation of the two approaches is not significantly
depending on the rotor speed.
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Thank you
for your attention
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