Transcript Pre-PDR Presentation

Corona Threshold Voltage
Team Tesla:
Chris Rowan
Anthony Thompson
Brandon Sciortino
Philip de la Vergne
Aaron Wascom
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Presentation Purpose
• This Presentation describes the preliminary design
for the electrical breakdown experiment by Team
Tesla for the LaACES Program. It fulfills part of
the LaACES Project requirements for the
Preliminary Design Review (PDR) to be held
February 5,2013
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Document Scope
• This Pre-PDR Presentation specifies the goal,
objectives, background, and requirements for the
electrical breakdown experiment and provides a
guideline for the development of this payload
under the LaACES Project. As such, these topics
provide the basic for developing the PDR
document and presentation.
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Mission Goal
• To study the effects of humidity and
temperature on the electrical breakdown of
the atmosphere to prevent sparking and
ensure safety.
http://www.scienceclarified.com/Di-El/Electric-Arc.html
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Science Objectives
• To conduct an experiment of the breakdown
voltage in air at varying altitudes
• To observe the effects that temperature and
humidity have on our expected recreation of
Paschen’s curve
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Technical Objectives
• Measure temperature, pressure, humidity, current,
and discharge voltage for the duration of the flight
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Science Background:
Electric Discharge
• Results from the creation of a conducting path
between two points of different electrical potential
• Three Types:
1. Corona Discharge
2. Spark Discharge
3. Brush Discharge
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Science Background:
Corona Discharge
• Occurs when the
threshold voltage is
breached
• Only requires a high field
strength
• Current ranges around
micro amps
www.ce-mag.com/archive/1999/novdec/mrstatic.html
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Science Background:
Spark Discharge
• Occurs when the
threshold voltage is
breached
• Complete ionization
between electrodes
• Maintained through a
continuous high voltage
source
http://www.ehow.com/how_5884896_avoid-static-shock-open-door.html
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Science Background:
Brush Discharge
• In between the corona
and spark discharge
• It may appear as
irregular luminescent
paths
http://www.electrotherapymuseum.com/2009/Protocakes/index3.htm
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Science Background:
Corona Threshold Voltage
• The potential at which corona is found to originate
• Ohm’s law regime
– Once the threshold is breached, current increase
proportionality with voltage
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Science Background:
Avalanche Effect
Ionization of neutral atoms becomes possible when the KE of free electrons increase
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Science Background:
Paschen’s Curve
• V=f(pd)
• The minimum of this
curve corresponds to
the minimum Pxd
product for which the
ionization effect is
maximal
http://www.sciencedirect.com/science/
article/pii/S146685640200067X
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Science Background:
Humidity
• Partial breakdown threshold reverses from
decreasing the threshold to increasing it once the
pressure drops below a certain point
– 20,000-25,000 ft.
• Humidity can affect the magnitude of the current
moving through the ionized air by up to 20% in a
pulse corona
• Pulseless corona and negative corona is not
affected by changes in humidity
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Science Background:
Atmospheric Conditions
• Flight profile of expected payload environmental conditions
http://www.aerospaceweb.org/question/atmosphere/q0090.shtml
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Science Background:
Temperature
http://www.green-planet-solarenergy.com/double-glazingmaterials.html
• Temperature decrease  ionization energy
increase  avalanche effect decrease 
breakdown voltage increase
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Technical Background:
Electrodes
• Electrode - an electrical conductor that is used to
make contact with a nonmetallic part of a circuit
http://www.mikeblaber.org/oldwine/BCH4053l/Lecture05/Lecture05.htm
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Technical Background:
Positive vs. Negative Corona
Positive
Negative
• More stable discharge • More self-sustaining
discharge
• Linearly sensitive to
changes in humidity
• Humidity has little to
no effect
• Produces less ozone
than negative corona • Can only be
sustained in fluids
that contain
electronegative
molecules
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Technical Background:
Electrode Geometry
• Point
– Small surface area
– Concentrated
electric field
http://cnx.org/conten
t/m42317/latest/
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Technical Background:
Electrode Geometry
• Plane
– Evenly distributed electric
field
– Larger surface area
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Technical Background:
Electrode Configuration
• Point-Plane
– Surface area
ratio
– Ionization
energy
http://www.imp.gda.pl/fileadmin/old_im
p/ehd/coronast.gif
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Technical Background:
Electrode Composition
• Surface
– Texture
– Impurities
– Surface Area
• Electrode Material
– Dielectric Strength
– Conductivity
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Technical Background:
Previous Experiments
A mathematical model of the modified Paschen’s curve for breakdown in
microscale gaps
Influence of Axial Magnetic Field on the Electrical Breakdown and
Secondary Electron Emission in Plane-Parallel Plasma Discharge
•
•
•
Stainless steel electrodes
Mean discharge current
determined by voltage
drop over R
Breakdown voltage is
mean value recorded
from Oscil.
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•
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Copper anode and SS cathode
Voltage increased by increments
and allowed to settle
Current spikes from 1 nA to
hundreds of mirco-amps
Voltage quickly reduced to zero
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Technical Background:
Measurements
• Measurements during flight:
–
–
–
–
–
Temperature
Pressure
Humidity
Voltage
Current
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Technical Background:
Environmental Sensors
• Temperature Sensor
– Small signal p-n junction diode
• Pressure Sensor
– Piezoelectric sensor
• Humidity Sensor
– Capacitive sensing element with on-chip
integration
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Technical Background:
DC to HVDC Converter
• An electronic circuit which converts a source of
direct current from one voltage to another
• Due to the payload size and weight restrictions, the
required voltage for discharge is improbable with
on-board batteries alone
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Technical Background:
Current Sensor
• Pico ammeter
– Voltage drop across resistor
• Radio Frequency Interference
– Band of frequencies produces upon discharge
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Science Requirements:
Spark Gap
• The gap distance shall be 1mm
• The electrodes shall be composed of copper
• The electrodes shall be rough and clear of
impurities
• The electrode configuration shall create a positive
corona discharge
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Science Requirements:
Power and Sensor
• The spark gap shall be provided with a maximum
of 4.5kV
• The payload shall record temperature, pressure,
humidity, voltage, and current across the spark gap
• The payload shall be fully operational throughout
the entire flight profile
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Technical Requirements
• The ammeter shall have a minimum accuracy to
the microamp range
• The HVDC shall operate in all environmental
conditions
• The output voltage of the DC to DC converter
shall be controlled through an on-board interface
• All data shall be time-stamped and real-time clock
must be synced to the payload GPS
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Technical Requirements:
LaACES
• The payload shall not weigh more than 500 grams
• The payload shall not exceed 3 oz / in2 on the
smallest face
• The payload equipment shall cost less than $500
• The payload shall have two holes 17 cm apart
running the length of the payload to comply with
LaACES management requirements
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Project Management:
Team Contract
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Team Meeting
Disciplinary Action
Communication
Version Control
Decision Making
Team Roles
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Project Management:
Organization
Task
Project Management
Science Requirements
Electronics
Flight Software
Mechanical Integration
System Testing
Calibrations
Data Processing and
Analysis
Documentation
Member
Anthony Thompson
Chris Rowan
Aaron Wascom
Aaron Wascom
Philip de la Vergne
Brandon Sciortino
Philip de la Vergne
Anthony Thompson
Chris Rowan
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Change Control & Update
Procedures
• Changes to this Pre-PDR document shall follow all
regulations set by Team Tesla’s contract and only
be made after approval by designated
representatives from Team Tesla and the LaACES
Institution Representative. Document change
requests should be sent to Team members and the
LaACES Institution Representative and the
LaACES Project.
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Project Management:
Master Schedule
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Reference Documents
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http://arc.uta.edu/publications/td_files/paniker.pdf
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http://fog.ccsf.cc.ca.us/~wkaufmyn/ENGN45/Course%20Handouts/15_ElectricalProps/07_ImpuritiesCon
ductivityConductors.html
http://prb.aps.org/pdf/PRB/v61/i16/p11109_1
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4075398
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http://www.ce-mag.com/archive/1999/novdec/mrstatic.html
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0720090
http://neon.dpp.fmph.uniba.sk/workgroup/media/documents/microdischarge_1.pdf
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=AD0430336
http://prl.aps.org/pdf/PRL/v90/i22/e224801
http://www.highvoltageconnection.com/articles/corona.pdf
http://www.dtic.mil/dtic/tr/fulltext/u2/a239940.pdf
http://ethesis.nitrkl.ac.in/2875/1/Full_Thesis_Print_04.07.2011.pdf
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0720090
http://www.irispower.com/pdf/newtechpapers/Investigation%20of%20the%20effect%20of%20humidity%20
on%20partial%20discharge%20activity%20in%20stator%20windings.pdf
143.53.36.235:8080/Medical/research/CoronaDischarge.doc
www.haefely.com/pdf/scientific/e1-19.pdf - Switzerland
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