Advanced

Capacitive power transfer to car through wheel - is it possible?

Hall, Sebastian (2012) In CODEN:LUTEDX/TEIE EIE920 20121
Industrial Electrical Engineering and Automation
Abstract
Introduction: This work aims to evaluate the possibility to transfer electrical
power from a metal plate to the steel-cord within a car tire. If the tire stands on the
plate, a connecting surface occurs which can be interpreted as a capacitor, where
the rubber compound acts as a dielectric.
Method: First the impedance of the tire is evaluated: An analytical model is
set-up to describe the system; a nite element simulation is made using the FEMM
software and nally measurements using a Hewlett Packard 4194A impedance analyzer
is made on a Dunlop SP Sport Maxx Tire.
Secondly, the possible power transfer is analyzed, both by creating an analytical
model including the wheel impedance and a load, and by doing experiments on
a real... (More)
Introduction: This work aims to evaluate the possibility to transfer electrical
power from a metal plate to the steel-cord within a car tire. If the tire stands on the
plate, a connecting surface occurs which can be interpreted as a capacitor, where
the rubber compound acts as a dielectric.
Method: First the impedance of the tire is evaluated: An analytical model is
set-up to describe the system; a nite element simulation is made using the FEMM
software and nally measurements using a Hewlett Packard 4194A impedance analyzer
is made on a Dunlop SP Sport Maxx Tire.
Secondly, the possible power transfer is analyzed, both by creating an analytical
model including the wheel impedance and a load, and by doing experiments on
a real tire. The experiments and simulations are conducted both with and without
a resonant inductor. LTspice models are made to support the practical results as
far as possible and to investigate the limits for the capacitive power transfer.
Finally, a discussion is held regarding which parameters that can be improved
to enhance the technique.
Results: The impedance measurements show that the impedance coupling has a
capacitance of around 200 pF, and an equivalent series resistance which is inversely
dependent on the frequency and has a value of 4400
at a frequency of 10 kHz.
The LTspice simulations show that the imperfections in the transformer and
the inductance that are used in the practical experiments give rise to a lot of losses.
This makes the results from the analytical model and the practical experiments
dier, especially when a resonant inductance is introduced.
For a square wave source voltage of 1600 V and 10 kHz, and a load of 50 k
,
the analytical model give a load power of 20.1 W with an efficiency of 89 %. The
practical experiments give a load power of 19.5 W with an efficiency of 81 % when a
DC-link voltage of 30 V which results in a voltage about 1600 V on the secondary
side of the transformer - is used. For the same source voltage and load conditions,
but with a resonant inductor introduced, the simulations give a load power of 34 W
with an efficiency of 89 %. The practical experiments give a load power of 25 W
with an efficiency of 76% (33 V out from the DC link).
Conclusion: This thesis shows that the impedance feature of the tire that is investigated
makes it inappropriate for a big electrical power transfer. The capacitive
element of the impedance can be compensated for with a resonant inductor, but the
resistive part of the tire impedance is much too big to pass a lot of electrical energy.
With a dierent rubber compound though, that would have a smaller dielectric loss
angle, the technique could be worth evaluating more. For example, a tire with silica
filler instead of carbon black filler - which is used in the tire of this project - could
be worth analyzing. (Less)
Please use this url to cite or link to this publication:
author
Hall, Sebastian
supervisor
organization
course
EIE920 20121
year
type
H3 - Professional qualifications (4 Years - )
subject
publication/series
CODEN:LUTEDX/TEIE
report number
5305
language
English
id
3710545
date added to LUP
2013-05-21 06:49:40
date last changed
2014-09-04 08:29:55
@misc{3710545,
  abstract     = {Introduction: This work aims to evaluate the possibility to transfer electrical
power from a metal plate to the steel-cord within a car tire. If the tire stands on the
plate, a connecting surface occurs which can be interpreted as a capacitor, where
the rubber compound acts as a dielectric.
Method: First the impedance of the tire is evaluated: An analytical model is
set-up to describe the system; a nite element simulation is made using the FEMM
software and nally measurements using a Hewlett Packard 4194A impedance analyzer
is made on a Dunlop SP Sport Maxx Tire.
Secondly, the possible power transfer is analyzed, both by creating an analytical
model including the wheel impedance and a load, and by doing experiments on
a real tire. The experiments and simulations are conducted both with and without
a resonant inductor. LTspice models are made to support the practical results as
far as possible and to investigate the limits for the capacitive power transfer.
Finally, a discussion is held regarding which parameters that can be improved
to enhance the technique.
Results: The impedance measurements show that the impedance coupling has a
capacitance of around 200 pF, and an equivalent series resistance which is inversely
dependent on the frequency and has a value of 4400 
 at a frequency of 10 kHz.
The LTspice simulations show that the imperfections in the transformer and
the inductance that are used in the practical experiments give rise to a lot of losses.
This makes the results from the analytical model and the practical experiments
dier, especially when a resonant inductance is introduced.
For a square wave source voltage of 1600 V and 10 kHz, and a load of 50 k
,
the analytical model give a load power of 20.1 W with an efficiency of 89 %. The
practical experiments give a load power of 19.5 W with an efficiency of 81 % when a
DC-link voltage of 30 V which results in a voltage about 1600 V on the secondary
side of the transformer - is used. For the same source voltage and load conditions,
but with a resonant inductor introduced, the simulations give a load power of 34 W
with an efficiency of 89 %. The practical experiments give a load power of 25 W
with an efficiency of 76% (33 V out from the DC link).
Conclusion: This thesis shows that the impedance feature of the tire that is investigated
makes it inappropriate for a big electrical power transfer. The capacitive
element of the impedance can be compensated for with a resonant inductor, but the
resistive part of the tire impedance is much too big to pass a lot of electrical energy.
With a dierent rubber compound though, that would have a smaller dielectric loss
angle, the technique could be worth evaluating more. For example, a tire with silica
filler instead of carbon black filler - which is used in the tire of this project - could
be worth analyzing.},
  author       = {Hall, Sebastian},
  language     = {eng},
  note         = {Student Paper},
  series       = {CODEN:LUTEDX/TEIE},
  title        = {Capacitive power transfer to car through wheel - is it possible?},
  year         = {2012},
}