See remarks below.
Jon D. Curtis, PE
Curtis-Straus LLC [email protected]
One-Stop Laboratory for EMC, Product Safety and Telecom
527 Great Road voice (508) 486-8880
Littleton, MA 01460 fax (508) 486-8828
http://world.std.com/~csweb
On Thu, 31 Jul 1997, Jerry Martin wrote:
> I've been asked to test a network powered (-130 Vdc) product to
> GR-1089-CORE for lightning and power cross.
>
> Does anyone out there have any suggestions on how to do this testing
> while the product is powered?
>
> The problem is that if you apply 1000 V, 10/1000 uSec, 100 A to tip/ring
> while the product is powered, you will damage the power source. I've
> looked into using series inductance followed by an MOV and capacitor, but
> I'm not sure if all the energy is getting to the UUT. Another problem is
> that my tester applies a short to tip and ring prior to the application
> of the test voltage.
To protect the power supply add as much resistance as you can push the
required amount of current through. Then add a 2-10mH inductor (you can
buy commercial or cut up a line filter). Make the protection two pole
with capacitors (5uF to ground ought to do) and non-linear with MOVs rated
just over 130VDC.
To keep the EUT running during the power supply shorting action use a
large capactor in series with the generator. You'll need to use a fairly
large one to avoid cliping the trailing edge of the short circuit current
waveform. Without running calcs, I believe the ballpark is 1000uF for a
5-10% reduction in short circuit fall time. Hopefully, your generator is
a little long so that you can shorten it down to 1000uS.
>
> The same problem doing power cross (600 Vac, 1 A, 1 Sec). Applying this
> kind of voltage to the power source will damage it. Is there a way for
> the UUT to remain line powered and provide protection to the power
> source?
Seems to me you could use something like the loop simulator from part 68.
Protect the DC power source with 10 Henry inductors in series with each
lead. Check this out by placing a capacitor (say 1000uF) across the power
supply end of the inductors (sans power supply) and measure the voltage
on the cap with a volt meter (it ought to be real low). Be cautious with
this set up because inductors with less than 1500V dielectric withstand
capabilities are likely to become "fire or fragmentation" hazards. With
Surge and Overvoltage testing eye protection is not optional.
>
> Has anyone had similar problems?
>
> Thank you very much for any suggestions.
>
> Jerry
>
