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in the previous video we performed an
electro thermal analysis of an IGBT
based inverter by coupling ances q3d
extractor and ANSYS icepack in this
video we'll perform post-processing on
the solution and come up with an
improved design for the IGBT we begin by
generating the temperature plots in
icepack select the objects that were
included in the electro thermal
simulation right-click can go to extend
selection all object faces now
right-click anywhere in the modeler and
go to plot fields and select temperature
in this dialog select the steady-state
solution under quantity select
temperature and in volume select all
objects press done the temperature plot
is created we see the overall
temperatures range from 30 degrees C to
114 point five degrees C
next we'll generate the current density
plot and q3d extractor remember we set
up a load of 100 amps through the device
you can see regions of high current
density at the metal bridge there are
also high currents at these points
because of those temperatures are also
high in these Junction regions of the
semiconductor chips the temperatures of
the wire bonds are also high there's
also a hotspot at this Junction
temperature ratings for typical IGBTs
are shown here the temperature is
predicted by QD and icepack are within
safe operating limits but we can make
the design more robust by reducing the
temperatures so what can we do to lower
the temperatures of the hotspot regions
one way to do this is to decrease the
resistance of the junctions this can be
achieved by increasing the cross
sectional areas of the junction regions
the area of this junction region is 45
square millimeters
here's my modified design the area of
this Junction region is only sixty
square millimeters more than the
original model I also made this Junction
thicker increasing its area by three
hundred and thirty square millimeters
I've also doubled the area of this
Junction from twenty to forty square
millimeters so these are relatively
minor modifications to the original
design I added another ice pack design
for the modified geometry as before I've
linked the e/m power losses from Q 3d to
ice pack now I'll run the simulation
once the simulation ends we can generate
the temperature plot the maximum
Junction temperatures are much lower now
they are ninety three point five degrees
centigrade that's twenty one degrees
lower than the original
moreover the maximum temperature in this
new design is over eighty degrees below
the maximum permitted temperature of one
hundred and seventy five degrees
centigrade this modified design is a
significant improvement over the
original design lowering the junction
temperatures of the IGBT increases its
reliability we can explore the benefits
of the improved design by varying the
temperature of the surrounding
environment at
sure of 40 degrees the analysis predicts
a maximum temperature of 113 point five
degrees C for the modified design and
134 degrees for the original therefore
the modified design has twenty point
five degrees more safety margin before
it can overheat and damage the IGBTs
this should improve the reliability
significantly at high ambient
temperatures
you
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