Hi Jack-
That's always been my biggest problem in that regard; whether it was the
old charts or Doug's calculator. I ask the eng. what's the worst case
current draw... they say something like, "Well, 20 amps at motor stall I
guess, but the current drops off quick as the temperature rises." So what
is "quick"?

Maybe you've already seen this, but the only reference material I can point
you at is also on Ultracad's site,
http://www.ultracad.com/fusing.pdf

Hope it helps,
-Chris





                       "Jack C. Olson"
                       <[log in to unmask]>            To:   [log in to unmask]
                       Sent by: DesignerCouncil          cc:
                       <[log in to unmask]>         Subject:    [DC] Trace Heating

                       10/07/2004 02:34 PM
                       Please respond to
                       "(Designers Council
                       Forum)"; Please respond to
                       "Jack C. Olson"







It seems like everyone is asking me questions I can't answer today.

We have been using the thermal trace calculator from UltraCAD
( http://www.ultracad.com/calc.htm )
but today someone asked me how time affects the temperature.
For example, what if the trace is only energized for half a second?
How hot will it get? Or how about a 50% duty cycle?

I can't seem to find any info about it. Anyone have references?

Jack (aka "one hot board designer")

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