The AM Forum

Hi Guys,
   I'm looking at a schematic for a U.S. military 28V, 50A power supply. It is a PP-4763/GRC. I'm puzzled by the designation for an inductor that is between the transformer secondary and the full wave bridge.
   It is labeled as: 3,36 X 10-
                          VOLT-SEC

   I know that Henrys can be expressed as VoltxS/Amp but this still doesn't make sense to me.

   Can anyone translate this for me?

Thanks,
Ed/KJ4JST

This might help:

http://www.electronicsweekly.com/blogs/electronics-weekly-blog/2008/03/an-engineer-in-wonderland-what-do-voltseconds-look-1.html (http://www.electronicsweekly.com/blogs/electronics-weekly-blog/2008/03/an-engineer-in-wonderland-what-do-voltseconds-look-1.html)

Otoh, I am unsure how to make the conversion from Webers (volt-seconds) to Henrys...

               seems like an odd way to spec a part in a schematic. Post the schematic?

I think page 5 of this pdf explains the relationship.

http://www.ece.msstate.edu/~donohoe/ece3183inductance_and_capacitance.pdf (http://www.ece.msstate.edu/~donohoe/ece3183inductance_and_capacitance.pdf)

Now that I said all that, I read what you wrote. It's between the transformer secondary and the bridge rectifier?? That would imply that it is for getting rid of switching harmonics looking back into the xfmr and the ac line... I'd expect that it would have to be small enough in inductance as to not effect the 60Hz. AC... Also at 50 amps there's some serious current draw and likely some serious switching spikes in the rectifiers as they try to keep the capacitor/filter bank charged. Guessing.

That's a *hefty* supply!

1 Henry = (1 Weber) / Amp

Thanks for your comments, guys. Bear, your links were very informative.

I'm still puzzled by the units on the schematic. First is the use of a comma in the "3,36". I know that Europeans use a comma instead of a decimal point but this is US military and decimal points are used everywhere else on the schematic. Second is the absence of amps in the dimensions.

I'm still trying to figure out how to scan and attach the schematic to a post.

Ed

It sounds similar to the inductor used in tube type auto radios that was installed before the on-off switch. Maybe 10T of heavy wire about 1"L and 1/2" D; not very much L and bypassed by a .5uF cap usually. Those old electrical systems could generate some serious crud; the radios even had a spark plate.

Carl

Here is a section of schematic that shows the inductor in question. At least I hope it is viewable. It is to the right of and nearly level with top of bridge.

How strange. I know that supply well but don't remember ever having trouble with that inductor, can't even recall where it was mounted. For commutating, to help shut off the SCR. I think the -34 TM on the unit is attached. It is available on LOGSA as "A" unrestricted.

"REACTOR L2:
Connected in ac supply to bridge rectifier.
Introduces time delay needed to operate SCR1 (Q1)."

Opcom,
   Incredible! This is info I needed badly. I've been working off a schematic only.

   I have the transformer, meters and L1 from the original power supply and I have most everything else from my "junk box". L3 was the puzzle. The info you've supplied should solve my problem.

   But, as to the original question, do you know what the specs mean? :)