Magnetics Business & Technology - July/August 2023 - 30

VISIONS
Marsilli's Distributed High-Density (DHD) Stator Winding Technology for High-Efficiency
Motors
By Kumar Rajasekhara, CEO & President, Marsilli North America
Introduction:
In the rapidly evolving
world of electric motors,
two technologies
for high-performance
wound stators have
primarily dominated
the production technologies
landscape:
Hairpin and insertion.
Each brings its own
set of advantages to
the table; however,
they also carry inherent
limitations that
inhibit their efficiency
and performance.
Notably, Marsilli,
a global leader in
electric motor winding
and assembly systems,
has introduced
an innovative Distributed High-Density (DHD) stator winding
technology, engineered to amalgamate the merits of the existing
technologies while adeptly addressing their shortcomings.
Limitations of Hairpin and Insertion Technologies:
Hairpin technology, characterized by its utilization of solid, flat
copper bars bent into a hairpin shape, inserted into the stator
core and then welded, boasts various benefits such as high
slot fill factor, low wire overhead and low wire stress. However,
it is known to experience the " skin effect " at high speeds due
to the wide surface of the bars. This phenomenon results in
a lower motor efficiency at high speeds in comparison to the
power consumed, thereby hampering its overall performance.
Other limits of this technology are the limited flexibility in term
of wiring schemes and wires per slot on top of the high number
of welding joints.
Conversely, the insertion technology involves the preparation
of pre-formed coil of round copper wire that are then pulled into
stator slots. This traditional approach, though providing certain
advantages, grapples with the randomness in copper wire
positioning and a low filling factor. The ensuing lack of order
and density in wire placement negatively impacts the efficiency
and performance of motors built on insertion technology. It also
includes a high risk of wire damage and a considerable wire
overhead.
The Birth of DHD Stator Winding Technology:
Seeking to offer an alternative to the motor market from the
traditional insertion and hairpin technologies, Marsilli has
pioneered the Distributed High-Density (DHD) stator winding
technology, skillfully combining the best aspects of the existing
approaches while mitigating their downsides. Marsilli's patented
solution adopts thin round enameled copper wire wound
in precisely-layered pattern maximizing the slot filling factor,
thus minimizing the stator DC copper losses. Moreover, the
30 Magnetics Business & Technology * July/August 2023
use of multiple strands in hand significantly reduces stator copper
AC losses due to skin effect. The DHD winding technology
also implements a complete turns transposition which also is
strongly effective in minimizing the high-frequency stator copper
AC losses due to proximity effect.
The presence of the pole shoe and the possibility of adjusting
the slot opening width as necessary, result in a torque ripple
reduction, which means also a reduction in mechanical vibrations.
Another important DHD feature is the wire connections
minimization, leading to fewer welding points, hence a cleaner
and more reliable process.
Marsilli's DHD stator winding technology offers a flexible, scalable
cost-effective solution for electric motors with high filling
factor and low losses at high frequencies. It can be employed
across a range of motor sizes, lending itself to diverse sectors
and applications. DHD-wound prototypes have already
been manufactured and tested. Testing data has been used
to compare DHD-wound prototypes performance with Hairpin
motors with similar features. The results showed a comparable
efficiency at lower speeds, thanks to the similar copper filling
factor thus similar DC resistance, and much better efficiencies
at higher speeds thanks to DHD copper AC losses minimization.
The proven high-speed efficiency differential of the DHD
motor as compared to the hairpin motor reached values up to
+6%.
Conclusion:
Marsilli's pioneering DHD technology stands to revolutionize
the electric motor industry by addressing the limitations of
Hairpin and insertion production technologies. After a four-year
journey, Marsilli is announcing that the technology is finally
mature. Marsilli is already involved in several pilot projects and
looks forward to collaborating with partners and customers on
new concrete projects to bring this innovative technology to the
industry forefront.
Author Bio:
Kumar Rajasekhara holds a
degree in Mechanical Engineering
with a concentration in Machine
Design from the University of North
Carolina at Charlotte, as well as
an MBA in Marketing and Finance
from Loyola College in Maryland.
He began his professional career
as a Machine Design Engineer for
packaging and steel companies.
For the past 36 years, he has
worked in the coil and motor winding and automation industry
in various engineering, sales, and operations positions. He was
appointed as President and CEO of Marsilli North America in
2004. During his tenure as head of the wholly-owned subsidiary
of Marsilli, he positioned the company as one of the most
significant suppliers of winding and assembly equipment in
North America and expanded its presence by opening Marsilli
subsidiaries in India in 2006 and Mexico in 2016.
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