DC Resistance versus AC Resistance in Q3D
by: eustacec
email:
eustacec@nus.edu.sg
12/17/2002 5:55A
Hello, I have a question on quick3d. I have run a simulation which shows that the DC resistance value is HIGHER than the AC resistance. Can this happen? and Why. Theoretically, the AC resistance is due to the skin effect, and it will always be bigger than DC. 2nd situation where I have 2 different conductors in series. Copper + Solder. How does this impact on the DC and AC? Your reply is appreciated. Thank you. Cheers.
Re: DC Resistance versus AC Resistance in Q3D
by: Richard Remski
email:
remski@ansoft.com
3/3/2003 11:41A
The AC solver doesn't 'know' what skin depth is, so it assumes that the current is in the 'surface' of the conductor only. This curve is valid for frequencies up where the skin depth is less than the real conductor thickness, but is going to be incorrect at really really low frequencies. The DC solution on the other hand does assume currents thru the whole thickness, so its answer is more 'valid' for those very, very low frequencies. So no, higher AC than DC resistance shouldn't happen in real life....if you see it that's an indication that for the frequency you're looking at is in that transition region where the AC assumptions are breaking down. RTR