Saturday, February 6, 2010
Prob 19.6 Rcrit
The problem description states that we want Rcrit to be at least 200 Ohms, but while going through steps b & c I never used this value to make any design choices. When I plug my calculations back in I get Rcrit = 175 Ohms for part d, which does not match the design. Should I have used the 200 Ohm value from the problem description in the calculations, or do I probably just have a math error somewhere?
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19.6d
Rcrit=268 Ohms
pb19.6 is the same as the example in lecture 9.
Rcrit is found in lecture 9, annotated slide 15.
Where your parameters the following:
Hinf = 3.68
I = 2.82
Zoo = 520
Isc = 2.88
Voc = 1500
These give me Rcritical = 318
I calculated Isc = 3.04A. I used Voc = 750V because 1500V is peak to peak. In the example problem the voltage is only a peak voltage. Does this seem correct?
I did the same as you for Isc, AB.
thanks......I'm in line now.
could someone confirm their results with my Ipk values:
I get around 2.5A and 3.0A. This will validate our component selections right away.
Hi Brandon,
I chose to have Cs=Cp, which I calculated to be 2.7 nF, that results in L = 9.8 mH. My Xs = 112.6 ohms and my Xp = 246.7 ohms.
As a result my peak values are 3.03A for open ckt, and 3.6A for short ckt.
You previously mentioned that you may have been using 1500V, did you change your H_inf?
Xs = Zoo/H_inf = 245.58/1.8408
Xp = Xs(H_inf/(1-H_inf))
I do get your Cp value but none of the others. My Isc aligns with your value listed.
Note that Cp = (1/(Xp*w))
= (1/246.7*(2*pi*200e3)) which doesn't equal your Cp value
Let's check that first....
I am using the formula in the book (19.69) to solve for Cp, which is equivalent to what you used except when broken down it is
Cp = (H_inf-1)/(2pi*fs*246.7)
I get Cp = 2.7 nF
Our peaks are very close, probably just a little calculation difference/error on my part
I'm thinking their is a problem with your Xp....246.7.
Yes you are correct, good catch thanks.
I just recalculated everything, and I get 2.55 and 3.03 which is the same as your peak values.
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