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CEDRAT News - N° 64 - February 2013
Power Electronics SMC inductive components
optimization with Flux 3D.
Dr François Bernot - FranceCol.
F
ranceCol is an innovation industrial company that develops
its own power electronics drives and electrical machines
& components. One of its R&D projects consists of SMCbased (soft magnetic composite) inductances & transformers,
to improve Power Electronics.
FranceCol has industrial partnerships that provide real industrial
vision and support for its customers. FranceCol develops and
manufactures a comprehensive range of power electronics
converters itself, from 10W to 50kW, with two different customer
targets:
• Lab oriented products, for didactics, research, or fast
prototyping industrial purpose  modular design
• Mass production-oriented compact power converters 
frozen design
Let us precise that innovation keys are held by:
• New ideas (enhanced by scientific capability)
• New technological vector to apply ideas
- SMC 3D flux isotropic paths
• Industrial capability in order to transfer innovation into the
real world at efficient cost and investment.
http://www.francecol.com
Power electronics inductives
FranceCol modular power converters are built around the next
general purpose electronic frame. With a set of copper bars, it
can perform any voltage dc bus powered structure.
This feature is very interesting for fast prototyping in industrial
projects, because the hardware is ready to be plugged in, and
reprogrammed. For fast prototyping modular design applied to
power electronics, it is important to use optimized and modular
inductive components.
Modular rack
3kw to 10 kw
Customize application
• Transformer
• Harmonic filter
• Inductances
• Communication
• Relay
• Security
(continued on page 15)
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CEDRAT News - N° 64 - February 2013
Stray capacitance optimization
Power electronics applications impose stray capacitances to be
reduced. Indeed this parameter induces hard sub-oscillations,
especially during fast transients (transistors commutations).
It can be demonstrated that this parameter is directly correlated
to the induction level of iron parts. Less induction requires more
turns, and therefore more interface area between windings.
Many patents and ideas exist concerning winding optimisation
to optimize stray capacitance, but the main impact on this
parameter remains saturation level. The next figure presents
magnetization curves of ferrites, SMC & iron sheets.
Ferrite / Iron / SMC magnetization
It is interesting compare the best fields of each technology,
with overall size criteria, regarding operative peak induction,
with constant iron losses (imposed by case):
• Ferrite 1kHz at 0.3T to 100kHz or more at 0.1T
• SMC 400Hz at 1.4T to 10kHz or more at 0.4T
• Iron sheet 50Hz at 1.6T to 1kHz or more at 0.2T
losses. Considering that most power electronics applications
operate below 20 kHz, SMC is a very good alternative to ferrite,
when iron sheets are no more available.
Stray inductance optimization
With inductances, especially in transformers, stray inductance
optimisation (minimization or imposed value) is a real
constraint for power electronics designers. Undoubtedly
inductance with low external leakage flux is good, because
it allows close external shielding, with no interference. The
transformer case involves a similar problem, whatever the
required Blondel parameter (leakage flux relative inductance
set). Many designs specify a given value for this latter parameter.
Introducing airgap will induce high disturbances and EMF
problems. SMC 110i-5P grade, that gives a distributed airgap
in place of a physical airgap, is a good answer.
Another option to optimise stray inductance is to use 3D core
design. If “pot like” cores are well known with ferrites, they are
not common with SMC, and impossible with iron sheets.
Given SMC processing constraints, it is important to develop
industry-friendly cores, ready to be mass-processed. We don’t
have the space to detail process constraints in this document,
so will just mention brainstorming meetings with mechanics,
chemists, physicists, electronics and electro-technical
engineers, each time a design is to be launched: everybody
bringing opposite constraints…!
The next figure presents 3D design, with an extra screening leg.
More room for flux
=> more energy
=> less cooper
=> screening effect
3D extra leg
transverse flux losses
with iron sheets
(none with SMC)
where SMC is design and processed. It is therefore no use to
ship confidential schematics far away…!
The next figure presents Flux 3D optimisation of a medium
frequency pulse transformer. Stray fluxes are important as
parameters, because they have a substantial impact on metal
case design.
The impact of linking pieces on saturation level, causing stray
fluxes in fast transient modes (power IGBT commutation), is
clear in this case. Flux 3D allowed reliable and efficient fast
prediction of the transformer, using various configurations. A
comprehensive set of SMC inductive components is now under
study at FranceCol.
FranceCol facility at Luynes (France)
Our facility includes all the resources needed for electrotechnical design, industrial study and prototyping.
Creativity is completely open with SMC, while main interest of
SMC design concepts comes from full French industrial process,
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