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Old 15th March 2013, 05:06 PM   #36731
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Quote:
Originally Posted by bcarso View Post
Talk about one extreme (batteries) to another.
After which the outputs of both smps blocks are filtered several times the oldfashioned hardware way : 72.600uF total.

Me sorta grew up with this beauty, she went to bed when I left for university.
(3-cilinder submarine, L+R battery of 168 cells of 2.1V, instead of Forward + Back battery)
All-DC, with 350V-1500A through a 400mm2 cable (subs require far less power submerged), only Biot-hazard law complaints.
Thyristor noise and SMPS hash would have been some fun.

Silence is Golden.
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Old 15th March 2013, 06:15 PM   #36732
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The constant voltage transformer (Sola) work by running the transformer at saturation. They have a harmonic neutralization (big cap) to remove the excessive harmonics but are usually running around 3-5% THD at least. They all buzz. Its magnetostriction and really no amount of potting can remove it. The steel itself is expanding and contracting and has a lot of force behind it. Transformer acoustic noise is a bigger real headache than the radiated fields and much harder to get rid of. Usually if you can't hear it your listening room is too noisy for quality listening. Its rarely inaudible. Export to Japan if you want a crash course in this.
The resonant cap is usually tuned to increase the 3rd harmonic. they are usually run at 1.9 and 2.1 so quite heavily into saturation, I was tasked with working on small ones usually potted in a wound strip steel enclosure, with extra blank lamination strips stuffed in before the potting compound was added to keep the external field down.
The best case minimum power was about 30% of max, more usually run between 60% and 100%, and usually designed for +-10% mains, ocasionally more.

at the place I worked at the largest was 750 watt, smallest about 60 watt.
for best result you need skinny laminations, but that means more offcut from a strip sheet run through the E/I cutter.

That is also for Pano

The large amount of 3rd gives an easy long conduction angle for the diodes though...
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Old 15th March 2013, 09:43 PM   #36733
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Well I ran a bit more than 100 measurements today on power transformers. Attached is one of them.

This shows the harmonic distortion of a flatpack style transformer with dual bobbins. A primary and secondary on each bobbin. It is measure both with and without a 25 ohm load across series connected secondaries. Since each should be 12 volts that gives just about a 1 amp draw. Input voltage is 120 or 120 x 1.1 (130 ish) at 50 hz.

My conclusion is that it should be loaded with a 10 uf capacitor across the secondary in most uses.

Note the distortion does increase with higher voltage, but not as much as from lower frequency when compared to the 60 hz curves.

I'll show more later if anyone is interested.
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Last edited by simon7000; 15th March 2013 at 09:53 PM.
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Old 15th March 2013, 09:59 PM   #36734
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Simon,
Where you are in PA the power is sourced at 50hz? I have been under the assumption that all US power was a 60hz source.
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Old 15th March 2013, 11:27 PM   #36735
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Simon,
Where you are in PA the power is sourced at 50hz? I have been under the assumption that all US power was a 60hz source.
Actually until recently there were some areas with 25 hz power! DC was used in parts of New York City until a few years ago.

But I am using the signal source in the AP analyzer and an Ashly PE3800 amplifier in the bridged mode.

I also ran curves at 60 hz. I will do some frequency response curves later.
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Old 15th March 2013, 11:34 PM   #36736
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That must have been some old Edison power to still be using dc power after all these years. I thought that Tesla won that war years earlier!

Was the 25hz from some old hydroelectric power from Niagara Falls or something?

Last edited by Kindhornman; 15th March 2013 at 11:37 PM.
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Old 15th March 2013, 11:37 PM   #36737
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Quote:
Originally Posted by simon7000 View Post
Actually until recently there were some areas with 25 hz power! DC was used in parts of New York City until a few years ago
Except that was only for some selected "ancient" equipment like those elevators that had a concierge to operate them. Many subways are still DC and 16 2/3 Hz is still used in Europe for trains. Long haul power transmission has also revisited DC.
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Old 15th March 2013, 11:51 PM   #36738
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Nov 14 2007 New York Times had the article about Con Ed dropping DC service and how they went to converters! I don't know how to past the web info on this phone, but you should be able to find it.


BTY many elevators still use DC. AC motors try to start up and lock on frequency-speed so they require complex controls. DC is current to torque and naturally provides smooth motion.
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Old 16th March 2013, 12:02 AM   #36739
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Originally Posted by simon7000 View Post
Nov 14 2007 New York Times had the article about Con Ed dropping DC service and how they went to converters! I don't know how to past the web info on this phone, but you should be able to find it.
Yes the point is there were not DC powered wall outlets (with warning signs "Don't plug ANYTHING into this"). Con Ed subsidized in some cases the converters to operate legacy equipment.
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Old 16th March 2013, 12:27 AM   #36740
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Originally Posted by simon7000 View Post
My conclusion is that it should be loaded with a 10 uf capacitor across the secondary in most uses.
Interesting work. Will this be an article on Linear Audio or something?

When you get round to it, you could investigate the effects of a "swenson snubber" as well.

Different type of snubber - John Swenson - Tube DIY Asylum
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