Introduction
Results
Methodology
•
A transient is a small
surge or spike
•
With a constant potential, the Nichrome wire
took 180µs to reach its melting point
•
Can be a voltage
spike or current spike
•
When pulsed for 100µs, the wire took 440µs
to return to ambient temperature
•
Transient voltages
stress a device and
can cause malfunction
•
After allowing the wire to cool, a second pulse
lasted 180µs before the wire reached its
melting point
•
Transients are the
cause of almost 80% of electronic failures
COMSOL Data
Time = 100µs
Time = 140µs
Conclusion
• This theoretical wire works the same before and
after a transient pulse
• The unique shapes in the iso surface is an
indicator of a mesh that is too coarse.
• Because it is hard to measure all the physical
parameters, eg. resistive change as a result of
temperature, the theoretical model will not
match the physical model perfectly
This is a transient current
Figure 1: A graph of current in LTspice, a circuit simulation
software, that shows the voltage ‘spike’ that is caused by a
transient current.
The wire used was
Nichrome, this project
models a thin and
electrothemeral sensitive
wire.
The gauge used was 40,
which makes the diameter
of the wire 38 µm.
Human hair ranges from
17µm to 181µm.
Figure 3: The wire at 100µs.
Figure 4: The wire at 140µs.
The potential across the wire is 15V. At
100µs the center of the Nichrome wire has
reached a temperature of 1156.1°K.
The potential across the wire is 0V. The heat from
the wire is dissipating into the air around it. The
max temperature is now 1161.1°K.
Time = 550µs
Time = 720µs
Nichrome is used in
hair dryers, electric
ovens, toasters,
electronic cigarettes
and soldering irons.
Figure 2: A picture of the
geometry of the setup as
depicted by COMSOL.
RESEARCH POSTER PRESENTATION DESIGN © 2012
www.PosterPresentations.com
• Can simulate the results
of the transient current
What’s next?
• Use a finer mesh to get
more accurate results
• Experimentally verify
these results with a
physical model
Figure 7: The physical model
• A constant current source will be used to pulse
the wire
• Multiphysics simulation
software
• Can model the
properties of the
Nichrome wire, with
Copper contacts in air
• Based on these results, the physical model of
this setup would have to be tested with pulses
under 180µs
Figure 8: A circuit schematic of the circuit that will be used
for experimental verification as drawn in LTSPICE.
Figure 5: The wire at 550µs.
Figure 6: The wire at 720µs.
The potential across the wire is 0V. At 550µs
the center of the Nichrome wire has reached
a temperature of 295.71°K, within 1% of
room temperature.
The potential across the wire is 15V. At 720µs
the center of the Nichrome wire has reached its
melting point, over 1400°K.
Acknowledgements
Research Mentors –
Dr. Jennifer Zirnheld, Dr. Kevin Burke
Graduate Student – Daniel Muffeletto
Undergraduate Student – Sharece Blake