BTY, A simple power supply: 2 x 4700 uF filter, LM320/340 Regulators, 2 x 10 uF output was completely inadequate!
I know the fellow who has the patent on being born. I wonder if I can get one on breathing?
I wish you a good outcome with this test.
Main’s voltage here is 230V
See post #2 to #5
http://www.diyaudio.com/forums/equipment-tools/134065-b-h-curve-tracer.html#post1671926
for B-H curves with voltage varying +/- 10% from nominal value. Specs for 230V/50Hz allow –10% to +5% variation in voltage for to allow use of older equipment designed for 220V (which had specs for +/-10% variation)
What happened with the issue of human genes patenting?
George
My understanding was that the EU "Harmonized" the power spec across the EU by setting it at 230V +/- enough to allow 220 and 240 so no one had to change anything.
I like the idea of using two transformers but you could do the same with the Signal xfmr's by wiring the primary to 240 (on 120 mains) and then series secondary instead of parallel secondary. This will drop the internal flux a lot, and the VA rating a lot. Perhaps Ed can try this with his experiments.
I like the idea of using two transformers but you could do the same with the Signal xfmr's by wiring the primary to 240 (on 120 mains) and then series secondary instead of parallel secondary. This will drop the internal flux a lot, and the VA rating a lot. Perhaps Ed can try this with his experiments.
Load regulation is primarily governed by the size (power rating).
http://www.emcod.com/images/load_reg_chart.gif
For a given size trafo, low copper losses and working close to core saturation achieve good (low) load regulation. For EI units, the more filled is the winding window, the better.
For this target, one could also consider a ferroresonant construction
I understand although I am novice.
George[/QUOTE]
The two downsides to ferroresonants are the minimum power for regulation is usually quite high, and they are usually very loud.
I spent a year working with them before Uni
And one of the first things the UK power co's did was drop to 230 to give an instant free generating margin...
Actually the deal was that the outliers would have 5 years IIRC to converge to the common 230V.This is many years ago so I would thing that this process has been finalised by now.
jan
Speaking of power supplies, I see the new Sutherland phono preamp has a switcher. Talk about one extreme (batteries) to another.
Agree with Demian that a first-rate switching supply for audio apps would be a genuine advance. In particular, one which had at least two-quadrant operation (sinking and sourcing current) as well as exemplary low emissions would be greatly appreciated.
Agree with Demian that a first-rate switching supply for audio apps would be a genuine advance. In particular, one which had at least two-quadrant operation (sinking and sourcing current) as well as exemplary low emissions would be greatly appreciated.
George,
I just checked my PC-24-1000. http://www.signaltransformer.com/sites/all/pdf/PC.pdf It is an E-I core rated for two 12 Volt windings placed in series to give me 24 volts at 1 amp. I used an Ashly PE3800 amplifier in bridged mode and 26 db gain to drive the input. I used my Fluke Model 85 true RMS voltmeter to check the input voltage. I ran two sweeps at 120 volts and again at 131. Once with no load again with a 25 ohm 1500 Watt resistor load. The third harmonic distortion was the highest. It was never higher than -40 db re 60 Hz. All four curves were quite close on the harmonic structure.
With the load resistor connected the noise floor did rise.
I will run more transformers and post the results probably tomorrow.
I just checked my PC-24-1000. http://www.signaltransformer.com/sites/all/pdf/PC.pdf It is an E-I core rated for two 12 Volt windings placed in series to give me 24 volts at 1 amp. I used an Ashly PE3800 amplifier in bridged mode and 26 db gain to drive the input. I used my Fluke Model 85 true RMS voltmeter to check the input voltage. I ran two sweeps at 120 volts and again at 131. Once with no load again with a 25 ohm 1500 Watt resistor load. The third harmonic distortion was the highest. It was never higher than -40 db re 60 Hz. All four curves were quite close on the harmonic structure.
With the load resistor connected the noise floor did rise.
I will run more transformers and post the results probably tomorrow.
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No convergence on 230V. I think last time I checked it was well over 240V here. This allows more power to be sold without having to put in thicker wires, so the likely outcome of 'harmonisation' is that 220V areas will rise as high as they can get away with, while 240V areas will rise by a smaller amount.
How high?
I suspect that transformers sold as stand alone parts, that meet multiple standards may be better than low price sourced parts.
So I will run distortion at line voltage and + 10%, 50 and 60 Hz. I may even do frequency sweeps. But only to 10K at 120 volts. I don't want to smoke the amp.
it does depend how near the nearest transformer you are. The average definitely dropped by me since the Harmonisation, but when they have problems with nearby power it sometimes is given high. I have seen 210 to 240 at home. The 210 was distinctly dim in the that evening.
they have tap changers to keep it near a target range to average correct over the whole delivery area for each transformer.
Yes. The problem with keeping with specified tolerances is on the “former” providers of 240V. They should allow for almost zero plus tolerance (241.5V), just like DF96 says
Exactly! This is the USA (120V) version of the two transformers idea.
Wrinkle
Sorry for the meshed-up edit on #36692 post.
Me too have seen only large trafos of this kind.
So they vibrate due to harmonics in the magnetic circuit but the harmonics don’t show-up on the secondary voltage due to the electrical tank resonance?
Do they vibrate continuously regardless of the load, or only when the load varies abruptly?
Had you tried to fine trim the operation of the LC tank to match the behavior of the load?
This is good news.(well designed trafo)
Try to find out why (increased copper losses?). In theory and with well designed trafos, max magnetic flux is during idle (trafo unloaded).
Take your time. If I didn’t have to solve a problem with a bloody Musical Fidelity monster and settle some issues with a miniDSP, I would run some tests too. May be in a few days.
George
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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.
Not sure but it was conjectured that the overvoltage shutdown on various integrated power amps was to blame for the apparent failures.
I probably related the story of Frox (anybody remember them) having powered speakers supplied by Harman fail totally at a trade show. The designer elected to use amp chips characterized for automotive audio ("What could go wrong?"). I think it was at the now-long-gone Summer CES in Chicago, and the electricians were tired of complaints about low line, so anticipated a lot of loading.
Frox insisted on optical interconnections, so there was no easy substitution of other amps etc. After frantic efforts and days gone by, it was finally realized that the mains was just too damn high, and stepdown transformers were provided. But it felt like the beginning of the end for Frox and their innovative 10' solutions, nice-looking GUIs, very clever ergonomic remote, and the FroxBox, with a million expensive digital and mixed-signal parts under the hood. This was circa 1991 iirc.
Brad
Wow, there's a name from the past! I designed their controller (the hand-held one). I was not surprised to see them go belly up and sink.
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