On 10/7/2008, Ralph McDiarmid wrote:
Is it possible to insert a resistor between surge generator and CDN to
provide the correct impedance? Here is one source of high-voltage,
power resistors.
http://www.caddock.com/Online_catalog/high_voltage/high_voltage.html
Hi Ralph:
It is common practice to insert an external resistor in series with the output
of a surge generator to reduce the short-circuit current. In fact, some
standards call out different values of external resistance in their tests.
The resistor will influence the short-circuit current waveform, so you may
need to pay attention to that.
You must be very careful about the power rating and construction of any
resistors you add. The resistors must be able to handle the surge power, and
they must be non-inductive (not wire wound). Interestingly, one of the best
types of construction for this application is the old carbon-composition type,
but these are getting hard to find.
As long as the resistor construction you use is non-inductive, you can achieve
whatever surge tolerance you need by connecting several resistors in parallel.
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
[email protected]
http://www.randolph-telecom.com <http://www.randolph-telecom.com/>
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