Magnetising coil

Transcription

Magnetising coil

LABORATORIO ELETTROFISICO
YOUR MAGNETIC PARTNER SINCE 1959
STRUMENTAZIONE E APPARECCHIATURE
PER APPLICAZIONI MAGNETICHE
MAGNETIZING AND MEASURING INSTRUMENTATION
FOR MAGENTIC MATERIALS APPLICATIONS
FINITE ELEMENT ANALYSIS (F.E.A.)
IN THE DESIGN OF MAGNETIZING COILS
How does it works ?
the Customer’s samples are needed !
(0 days time)
FEA
calculation
the Customer’s drawings are of great help !
(3 days time)
mechanical drawing ready for assemblying prototyping coil !
(10 days time)
FEA calculation
the coil is ready !
(25 days time)
LABORATORIO ELETTROFISICO SRL 20014 NERVIANO (MI) ITALIA VIA G. FERRARI,14 TELEFONO +39 0331 589785 FAX +39 0331 585760
e-mail: [email protected] www.laboratorio.elettrofisico.com
What is F.E.A. ?
Finite element analysis is the most popular numerical method for the solution of electromagnetic field
problems: it is applied to a wide range of different applications and in the last two decades it lived a
strong increase also in this electromagnetism.
Laboratorio Elettrofisico has been using F.E.A. analysis for the design and optimization of its equipment
since 1991, when, especially among companies producing measuring and automatic equipments, it was
very unusual.
Figure 1: meshing of 2D geometry
(turn section in which electric current J is flowing)
Figure 2: magnetic induction around the turn
section.
Why using F.E.A. to design magnetizing
coils ?
The final step of any electromagnetic design is an experimental prototype, to verify the electromagnetic,
mechanical and thermal characteristics of the device: building up one or several can be sometimes very
expensive, especially if the device has a unique and complex geometry.
This is the case of most of Laboratorio Elettrofisico magnetizing and measuring devices, as most of
rotors, stators or actuators to be magnetized or measured are different in magnetic
properties or geometries from all the other ones.
Furthermore only by mean of a computer analysis it is possible to obtain many different models of the
device in a short time and to test very difficult solutions or too expensive to realize in an experimental
prototype.
Figure 3: radial magnetization of
NdFeB bonded ring . Internal
radius of the magnet was only 3
mm. Real magnetizing is very
small but very complex to
produce.
Transient electromagnetic and coupled
analysis
Most of the F.E.A. analysis in L.E. are performed to model very fast transitory phenomena, as
magnetizing process are obtained by capacitors discharge in a magnetizing fixture.
Laboratorio Elettrofisico: using F.E.A. in
magnetizing design
Sometimes an estimation by analytical model (by classical circuit modelling) is possible, maybe together
with the comparison of previous electric and magnetic results of “similar” previous device.
But usually in magnetism is not easy to create reliable models by classic circuit magnetic , as you deal
with non linear material, big flux leakage and sometimes also with Eddy currents effects.
Such approach is almost impossible if you are dealing each time with new design of motors, sensors or
actuators, what is usual in Laboratorio Elettrofisico: so each time “classic circuit models” should be
studied, tested and approved, which is not possible giving answer in few days or hours !
Actually, a realistic model can start only during the following steps:
Ø 2D model transient model, which can be performed also by the :
q
parametrization of the geometry and energy
q
optimization of the geometry and energy
q
validation of the best solution
Ø 3D static and transient model
o magnetic static analysis using current obtained in 2D transient analysis
and, sometimes
o parametrization of the geometry and energy
o optimization of the geometry and energy
o validation of the best solution
Ø Final device production and test: comparison with F.E.A. prediction.
Figure 4:
two poles bitter
coil (RAB
model). Detail
of the
magnetizing
field direction
and distribution
on a vertical
section.
Figure 5: rectangular bitter coil, 2 poles,
air cooled .
Figure 6: four poles - iron wound magnetizing fixture (CAF model).
Figure 7: four poles - iron wound magnetizing fixture: detail of the mesh (CAF model)
Figure 8: example of CAF model coil (air
cooled) and samples.
Figure 9: HE multipolar fixtures for
servomotors and generators and
samples
Thermal analysis
To obtain the minimum cycle time a thermal analysis is also possible: it is further more complex, as it
requires a 3D simulation (due to the 3D effect of cooling fluid flow) and the convective exchange are also
difficult to set.
But the details you can get with F.E.M. analysis cannot be obtained with other method and this can be
very useful as the high temperature area in magnetizing fixture are usually very localized in space (and
transient are very short, too).

Magnetising coil

Transcription

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