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Author Topic: HV Transformers(2)  (Read 30703 times)
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K5UJ
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« Reply #50 on: April 05, 2010, 12:26:27 AM »

Rob,

I looked through my Radio Masters catalogs (I have most of them from the late 50's through early 70's) but they were not of much use.  Although the catalogs are very large there were not a lot of listings for oil filled capacitors and the GE advertisements did not provide much information.  I did find that in addition to energy storage caps GE also made another group of oil filled caps that were designed for light duty coupling and buffering usage where the ripple is low and are known as the CP-70 series so make sure yours isn't in that model series.

On a side note, these catalogs are a generally great reference source (they run from 1,000-2,000 pages in length) and provided detailed specs on a lot of components.  If you see them hanging around at a hamfest they are worth picking up.  Mine came as a free bonus with my $75 Mosley CM-1 receiver and I have used them more than the receiver.



Rodger tnx vy much.  you didn't have to do that but I appeciate hearing about Radio Masters.  I looked at the Sangamo 8 uF 4 KV cap that came out of the broadcast rig p.s. and it is a bit smaller than the GE caps I ordered, but about in proportion for the value and voltage with the GEs and similar construction on the outside (i.e. the insulators) if that means anything, probably not much.  I'm pretty confident they'll be okay for testing and as someone, Carl I think wrote, the surefire test is to fire up the rig and run it for awhile and see if the caps are hot. 

Meanwhile, tonight I put a 5 v. drop transformer in an outlet box with a cord going to it to step the 120 v. line down to 115.  I want to free up a variac for more useful work.  I test it and read 118 v. and find my service v. has gone up 3 v. from 120 to 123.  Can't win.   Huh

Rob
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« Reply #51 on: April 05, 2010, 07:47:15 AM »

Rob,

You are welcome.  From what I could see in Radio Masters your caps are considerably larger than the energy storage caps and the only wild card are the GE caps that are neither listed for energy storage nor filter use.  Too bad they did not provide more detail but I will try to run down some info.  I will scan and post that page from Radio Masters for info purposes.

As to your line voltage, don't worry it will go back down again with the summer air conditioning load.  You really can't win Smiley
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Rodger WQ9E
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« Reply #52 on: April 05, 2010, 08:20:03 AM »

With all of the discussion of the difference in application for "energy storage" caps vx "filter type" caps. I wonder what is actually different in the physical construction of the capacitors?  Huh  Huh
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« Reply #53 on: April 05, 2010, 09:14:58 AM »

With all of the discussion of the difference in application for "energy storage" caps vx "filter type" caps. I wonder what is actually different in the physical construction of the capacitors?  Huh  Huh

I answered that yesterday.

Carl

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WD5JKO
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« Reply #54 on: April 05, 2010, 09:26:58 AM »


the difference seems similar to lead acid batteries; deep cycle versus normal car batteries. The deep cycle will be larger, and have thicker plates whereas the normal car battery has very thin and fragile lead plates.
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« Reply #55 on: April 05, 2010, 01:01:33 PM »

Rob,

You are welcome.  From what I could see in Radio Masters your caps are considerably larger than the energy storage caps and the only wild card are the GE caps that are neither listed for energy storage nor filter use.  Too bad they did not provide more detail but I will try to run down some info.  I will scan and post that page from Radio Masters for info purposes.

As to your line voltage, don't worry it will go back down again with the summer air conditioning load.  You really can't win Smiley
Thanks,
The line v. is usually dead on 120 v.  I wish it were lower but I have not seen it above that before.  I guess modern electrical loads can deal with input v. swings.  I pluged the 75A3 into the step down box and fired it up.  It made a little noise I had not heard before and I lifted the top lid and looked inside.  It sounded different and I didn't like that so I turned it off.  THEN I rechecked the line in the shack which of course, I should have done first.  It was 123!  coming out of the box, 118.  I'm gg to have to simply buy a bunch of variacs, put them in boxes with v. meters.

There are several problems with eBay, one being poor item descriptions.  I should develop the habit of asking questions on there.  Two other problems are sellers selling stuff they know nothing about, sellers ignoring categories (transmitters listed with receivers for example) and lack of subcategories.  There are around 20,000 listings for capacitors.  There should be sub-categories for air variables, micas, ceramics, oil, ...the same goes for other parts.  There are other problems but that is enough as I have already veered way off topic.

Rob
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« Reply #56 on: April 05, 2010, 01:23:30 PM »

There are around 20,000 listings for capacitors.  There should be sub-categories for air variables, micas, ceramics, oil, ...the same goes for other parts.

that would help... but just searching for "high voltage capacitors" shows a fair number of interesting (if expensive) ones, especially the Russian mil-surplus  Cheesy

I wonder how putting ten 560 uf, 450v electrolytics in series (with equalizing/bleeder resistors) would work instead?
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WD5JKO
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« Reply #57 on: April 05, 2010, 01:40:15 PM »

I wonder how putting ten 560 uf, 450v electrolytics in series (with equalizing/bleeder resistors) would work instead?


see reply 6 7 at:
http://amfone.net/Amforum/index.php?topic=17729.msg122355#msg122355
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WD5JKO
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« Reply #58 on: April 07, 2010, 11:46:18 AM »



Update, I got a reply from Aerovox concerning the 54 MFD @ 4400 vdc capacitor pictured at the beginning of this thread. So with an ESR of 0.2 ohms, I don't see a lot of heat from a amp or two of RMS ripple since for 2 amps, W=I^2*R, or 2^2*0.2 = 0.8 watts.  Take 800mw, and oil cool it in a cap the size of a 12oz beer can, and we should not get hot. I do see how a de-rate of voltage might be prudent. In my case, 3KV with a 4400 v rating puts it at 68% of spec. I think that would be fine. Any thoughts?

I pasted the Aerovox reply below.

Jim
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From: eperry AT aerovox DOT com
Sent: Wednesday, April 07, 2010 10:22 AM
To: Candela, Jim
Subject: Fw: Need Capacitor Spec Sheet
 Jim

Thank You for your inquiry.  The item listed below is obsolete.  Per our engineering dept this was a light duty capacitor and do not have  an RMS current rating.
The ESR would be 0.2 ohms.
If you have any technical questions you can contact the Engineer Paul Winsor 508-910-3178

Thank You
Ester Perry
Account Manager
508-910-3666
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KE6DF
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« Reply #59 on: April 07, 2010, 12:12:07 PM »

My thoughts would be that it would probably work fine at 3KV. As for the ripple, run it a while and if it doesn't get hot, it's probably good to go.

Be careful about putting your hand on it to check the temp while it is powered up.

I have one of the gun type laser IR meters and if you have one of those you could take the temp while it is running without touching it.

It might be interesting to call that Winsor fellow and see what he says about voltage derating and using it for a PS filter.
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« Reply #60 on: April 07, 2010, 12:35:31 PM »

It might be interesting to call that Winsor fellow and see what he says about voltage derating and using it for a PS filter.

I'd be interested too... makes "Working Voltage" rather meaningless if the cap won't work at said voltage  Roll Eyes

Meanwhile I am running a similar 56 uf, 4.2 kv cap at 3.8 kv standby, 3.6 kv idling current, will see how it holds up with my infrequent usage  Cool
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KM1H
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« Reply #61 on: April 08, 2010, 04:15:47 PM »

The operative phrase from Aerovox is  this was a light duty capacitor and do not have  an RMS current rating. .

Try the 68% and keep monitoring it as heating damage tends to be cumulative. I wont risk stepping on my crank and saying it will be fine but you have decent odds in your favor Grin

Carl
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