Download What state and other requrements

A mathematical model for a superconducting motor
What state and other requirements are necessary for a high efficiency superconducting
electric motor?
Joshua Mickelsen
Abstract:
High efficiency is becoming prominent in today’s world due to fears of the greenhouse
effect. This has caused the efficiency of motors to skyrocket into the high 90’s which is
meant to save money on electricity by not wasting it as heat. Despite this, there are still
some major losses of heat. One of the most notable of these comes from the mechanical
deficiency of friction between the axle and the housing that holds it in place. The aim of
this project is to make this effect negligible by suspending the axle without touching the
housing. This can be achieved using the assistance of superconductors on either end of
axle. Superconductors expel magnetic fields that stabilize levitation of rotor in relation
to housing, generating almost no heat from friction. Advantages include parts not
wearing out over time. Without parts touching, they can’t wear out and the machine
won’t break down because of mechanical problems. The second advantage is that the
efficiency of the device would increase because heat is not lost to friction which means
more work is produced for less input energy. This is similar to the design for a maglev
train whose benefits can easily be seen in both terms of speed and economy which is what
is expected from this motor. Ultimately the principles of the design of this motor are
solid, but due to some equipment malfunctions, my motor does not currently satisfy a
high efficiency motor.
Design Goals and Parameters for experiment
The object of this project is to create an AC motor in which the axle does not touch the
motor housing. This will be accomplished by suspending two superconductors on either
end of the induction rotor. The induction rotor itself will have to be a dewar so that the
liquid nitrogen coolant does not evaporate quickly. The drive mechanism for the motor
is simply a couple of electromagnets with a capacitor. As the electromagnets are turned
on, they will repel the diamagnetic induction rotor which will result in a spinning motion
free of solid-solid friction. An alternative method of levitation can be achieved by using
ac power to induce a current in a conducting surface. This generates a repulsive force
that can then levitate and be turned using an extra set of electromagnets. It uses the
same principles, but is modified to make up for the losses of resistance in traditional
conductors. It is not as efficient and is therefore not the preferred method.
Background Research:
Superconductors were discovered just a few years after liquid helium was condensed.
Oddly enough this was by the same person whose name was Heike Kamerlingh Onnes.
Onnes was measuring the resistance of mercury when he was surprised to see a sharp
decline in resistance that went to almost zero when it was cooled with liquid helium.
This became the first synthetic superconductor. Since then, it was discovered that
superconductors completely expel magnetic fields. They are able to do this thanks to
Lenz’s law which essentially states that when a conducting material is exposed to a
changing magnetic field, a current will run in the opposite direction of the magnetic field
and create a magnetic pressure between the tow. This means that superconductors can
shield objects from magnetic fields and levitate over magnetic fields. The magnetic
field does not even have to be particularly large for this effect to occur as a magnetic field
strength of 2 Tesla is what many maglev trains operate on. The amount of weight a
superconductor can support is limited by the strength of the magnetic field, distance from
magnet, area of superconductor, and critical magnetic field of the superconductor. This is
expressed in the equation Fm=(flux)^2/8pi*muon0x^2 where muon0 is the magnetic free
space permeability constant of 4pi*10^-7 and x is the distance between the magnetic field
and the superconductor. Superconductors are also widely used in MRI’s, supercolliders
and a large variety of purposes as none of the electrical energy is lost as heat as occurs in
a normal conductor. In fact, it is estimated that there should be no measurable loss in
electrical current of a superconductor even after a period of 10,000 years.
Superconductors can also be made into supercapacitors which can potentially hold as
much energy as a battery, but be charged in seconds. The applications of
superconductors are nearly limitless, but most of them have to be operated at very cold
temperatures which presents problems. There are two types of superconductors-Type I
and Type II as they were so aptly named. Type I superconductors generally need to be
cooled with liquid helium and have critical magnetic, electrical, and temperature
parameters which dictate when it is superconducting or not. Type II superconductors
generally operate at higher temperatures and were discovered in the 1980’s. They differ
from conventional superconductors in that they are not completely explained by the
theories of superconductivity(BCS) and by the fact that they can have mixed states where
part of the material is superconducting while another portion of the material is not.
Many of these Type II superconductors are ceramic and are very difficult to form into
wires which make them uncommon despite the fact that many of them can be cooled with
liquid nitrogen instead of helium. Superconductors are truly unique and their
applications limitless. Their unique levitation properties are why they have been chosen
for this experiment. AC levitation works off of similar principles and is also very
common to the world today. The only major difference is that the conductor that is
being induced with electrical current loses its power as heat and heat is therefore needed
to be replenished by a continually changing ac current. The maximum amount of
pressure that is generated from this is Fp=B^2/2muon0 where B is the strength of the
magnetic field and muon0 is the magnetic permeability constant. Magnetic field
strengths decrease with an inverse cube relationship whereas gravity decreases with an
inverse square relationship. It is because of this relationship that engineers place
electromagnets as close to each other as possible to increase efficiency. If one looks at a
solenoid, which is just a bunch of wire wound in a circle, then they will discover that the
magnetic field is constant within a solenoid, but degrades quickly outside of the magnet
and is practically nonexistent on the sides. This is why applications of electromagnets
occur near the ends of the magnet and not elsewhere. Ohm law is also very important in
my experiment as it has been used in numerous calculations. It relates power, volts,
amps, and resistance into a single system. They are all interconnected in a system and
allows us to increase some if we decrease others. If one increase amps then one will
increase the magnetic field strength in a solenoid according to the equation B=muon0nI
where B is the magnetic field strength, muon0 is the vacuum permeability constant, n is
the number of turns per meter length, and I is the number of amps. Therefore, if we add
more turns and increase the amps, then the strength of the magnetic field will increase.
Materials
1.Air insulated Dewar
2.2 disk superconductors that can fit inside the Dewar on opposite ends
3.4 powerful magnets on either side of a box
4.Liquid nitrogen
5.Wire for an electromagnet
6.Ac 12 volt transformer
7.Small capacitor
8.Aluminum Soda Can
9.Ac electromagnet
Procedure
a) Using an insulated glass container, insert two superconductors on either end of
the container and place aluminum foil around the outside of the container.
b) Secure a lid to the container that liquid nitrogen can be poured into.
c) Construct an ac motor with the transformer, wire, and capacitor (the rotor for the
motor will be the Dewar.)
d) Construct a box with magnets for the superconductors to be suspended from.
Pour liquid nitrogen into container until full and wait for superconductor rise.
e) Place electromagnets close to aluminum and turn on the circuit.
f) Leave until nitrogen boils off. Then turn off.
Ac Procedure
a) Construct an one large ac electromagnet and 10 electromagnets to support a
levitating structure.
b) Construct a levitating can out of a soda can.
c) Place levitation can in the middle of the apparatus and turn on.
d) Watch as the device levitates for ten seconds then turn off.
Data/Analysis
The dewar did not rise when subjected to liquid nitrogen which gives to reason that the
superconductors were faulty. When tested more strenuously, this was proved to be
correct and the faulty superconductors made it so that the prototype did not work. When
this project is to be retried, superconductors that actually work will need to be used.
This will allow the dewar to levitate which will provide a non-contact axle for the electric
motor. The second motor also proved unsuccessful at there were not enough amps to
create a powerful enough magnetic field to levitate objects. Making a high amp
transformer will fix this problem and allow for levitation. However, while this solution
is effective, it will waste so much power that it will not be a good solution to the problem
stated. The Superconductor listed in the first part will therefore be much better.
Conclusion
The project to build a motor with a levitating axle has thus far been unsuccessful. The
reason for this is due to faulty superconductors which made it so that the main portion of
the project was a total failure and thus made the entire project faulty. If this error is
corrected, then the motor should operate as expected. It will operate at much higher
efficiency than the ac motor and work better as it does not use a continuous strain of
energy to achieve levitation.
Sources:
http://www.open.edu/openlearn/science-maths-technology/engineering-and-technology/engineering/su
perconductivity/content-section-2.4
http://www.cdc.gov/niosh/mining/content/electricalandmachinesafety/proximity/hasard.html
http://www.engineeringtoolbox.com/air-properties-d_156.html
http://web.mit.edu/6.763/www/FT03/Lectures/Lecture8.pdf
https://en.wikipedia.org/wiki/High-temperature_superconductivity
http://www.physicsclassroom.com/class/thermalP/Lesson-1/Rates-of-Heat-Transfer
http://web.mit.edu/6.763/www/FT03/Lectures/Lecture8.pdf
https://www.youtube.com/watch?v=BFdq6IecUJc
http://chemistry.pixel-online.org/EP_home01d4.html?id=03&tp=03
http://www.scielo.br/scielo.php?pid=s0103-97332001000300027&script=sci_arttext
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&sa=X&ved=0ahUKEwi3qI2htN_KAhVDwGMKHfVXAM0Q_AUIBygB&biw=1252&bih=604#im
grc=7MMxNfuDjQWqcM%3A
http://www.futurescience.com/scintro.html
http://www.futurescience.com/scpart1.html
http://www.futurescience.com/kilns.html
https://en.wikipedia.org/wiki/Magnetic_levitation
http://www.electricneutron.com/electric-motor/single-phase-ac-motor/
http://www.electricneutron.com/electric-motor/single-phase-capacitor-sizing/
http://www.explainthatstuff.com/induction-motors.html
http://machinedesign.com/motorsdrives/single-phase-electric-motors-characteristics-applications
Research Plan and Post Project Summary
B. My project deals with superconductivity and its potential applications to increase efficiency and life
of electrical motors. Superconductivity is a solid principle that has proven applications in things like
maglev trains in Japan. The idea behind this motor is to put the track into a continuous circle which
reduces friction on the housing and axle which means more work is put into mechanical movement
and less is put into heat. In addition to this, there is almost no wear and tear on the parts which
means that the already long life motor will last much much longer. Superconductors are perfect to
tackle this problem because they can completely expel magnetic fields and hold enormous amounts of
weight which means it would fit this problem very nicely.
C. My Engineering goal is to produce a motor that increases efficiency and decreases mechanical wear
and tear.
D. Procedure
a) Using an insulated glass container, insert two superconductors on either end of the container
and place aluminum foil around the outside of the container.
b) Construct an ac electromagnet with an attached capacitor.
c) Construct a box with magnets for the superconductors to be suspended from. Pour liquid
nitrogen into container until full and wait for superconductor rise.
d) Place electromagnets close to aluminum and turn on the circuit.
e) Leave until nitrogen boils off. Then turn off.
Risk and Safety
This project does involve liquid nitrogen which is not a hazardous chemical because it is the
substance that makes up most of the atmosphere. It is however very cold and skin should be kept
away whenever possible, but gloves should not be worn because they could freeze and increase
contact time with skin.
Data Analysis
The success of this project will be based on whether or not the motor is held in place by the
superconductors and spins due to the magnet.
Bibliography:
http://www.open.edu/openlearn/science-maths-technology/engineering-and-technology/engineering/su
perconductivity/content-section-2.4
http://www.cdc.gov/niosh/mining/content/electricalandmachinesafety/proximity/hasard.html
http://www.engineeringtoolbox.com/air-properties-d_156.html
http://web.mit.edu/6.763/www/FT03/Lectures/Lecture8.pdf
https://en.wikipedia.org/wiki/High-temperature_superconductivity