Mick, Mike et al,
I recommend resistors from HVR. They have “non-inductive” resistors and
will help you decide what you need based on joule ratings instead of wattage
ratings. Sometimes they have some stuff in stock and they can let you know.
Often I end up putting their resistors in parallel or series to achieve the
values I need based on what is in stock as I usually don’t have a week or
more to wait. We have not had a single resistor failure and we use these all
the time for external networks.
http://www.hvrapc.com/products.asp
Jim
Jim Wiese
Senior Compliance Engineer
ADTRAN, Inc.
901 Explorer Blvd.
Huntsville, AL 35806
256-963-8431
256-714-5882 (cell)
256-963-6218 (fax)
[email protected]
Jim kindly did not mention I could follow through with a correct calculation -
I forgot the 0.72 factor. The Energy calculation should have read:
I assume you are trying to dimension the 500 ohm source resistor. A 500 ohm
resistor with a 1 A peak impulse current decaying in 50 µs will have an
energy dump of 0.72*500*1^2*50E-6 or 18 mJ. Although the peak VI power is 500
W the average power at one impulse per minute is only 0.3 mW (18 mJ/ 60s) - so
John is right continuous power rating isn't important
Mick Maytum
UK
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