Building a transformer

I ran across info on rectifier design up through filtering (but not regulation) at:

It is: Rectifier applications handbook - 272 pg - 2MB From a brief scan it looked very good and more than anyone here wants to know about rectifiers, including the physics.

A paperback book for transformers: Practical Transformer Design Handbook; Eric Lowdon; published by Howard W Sams; 240 pages; 8x11"; my copy is 1981. It is aimed at experimenters designing single transformers using salvaged cores. I thought it was very good. It may be hard to find, but with the internet who knows.

bud--

I've never found large bench supplies helpful for designing power amps.

Graham

Not as much as you might think.

Graham

10mA ? That'll power a pair of 5532s !

Graham

In the pro-audio market for sure.

Graham

Good link, Bud! Thanks!

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

In message , dated Fri, 11 Aug

2006, Eeyore writes

Not only. Of course, all the while the consumer industry can get away with a 2 uF in series with a tweeter with no magnet to speak of, why bother with active crossovers? But these things DO percolate down.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

In message , dated Fri, 11 Aug

2006, Eeyore writes

How quaint. Try different op-amps. In any case, two 5532s will do four active filters. Sallen and Keyes are quite good enough, unless you want to do tricks with phase.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

In message , dated Fri, 11 Aug 2006, Bud-- writes

Pages 93-97 contain assertions that are very much not true. Approach with great caution. The basic problem is that the difference between a rectifier resistively loaded and one with a filter capacitor is totally obscured, and in the later case, the impression is given that the rectifier still conducts for a full half cycle, whereas it conducts only for a brief period around peak supply voltage. As a consequence, the text on harmonics is rubbish.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

Need to backtrack on the maths a bit first. To get 50v dc regulated you need 50v dc +5v for regulator drop + 3v for rectifier drop + say 15% to allow for mains sag. Thats 66.7v dc.

Now to get 66.7v dc peak you need 66.7 / 1.414 = 47v ac.

To get +-50v dc you need the same transformer, no reason to have 2 windings at all. So you just need one 50v winding.

Now, current. If you play it within all specs you could use 5A x 1.6 =

8A transformer. But I built supplies for years when younger without using that 1.6 factor and never had any problems from the bridges or tfs, and since this is for personal hobby use I'd be tempted to do that. Or if you need something portable you could even go smaller and add fan cooling.

So you need 50v 5A = 250w transformer.

Toroidals are smaller, lighter, and more money. Microwave transformers should be avoided, they just need too many mods to be worth playing with.

I'd be asking myself if I really needed +-50v at 5A, and would be answering no. I once had a massive all singing psu and almost never used it. A small portable bench supply is a lot easier to use than a meatlump. For those occasional jobs that need more power I'd use something much more basic.

These days I'd buy one, or maybe look at modding a pair of pc psus if for some reaosn thats not an option.

NT

** Groper FROM HELL alert

** So a two diode voltage doubler ?? 50/60 Hz ripple ??

Bad idea.

** BOLLOCKS

The power tranny will COOK at full load with a 60% over current.

** BOLLOCKS.

The OP has specified +/- 50 volts at 5 amps = a 1000 watt DC supply.

Means a 1500 VA tranny for continuous operation.

** Finally, some sane advice.

An unregulated +/- 50 volt DC supply operated off a Variac is all the OP needs.

Just a 600 VA tranny with twin 40 volt windings plus bridge and two hefty electros.

...... Phil

"Phil Allison"

** Correction:

The OP has specified +/- 50 volts at 5 amps = a 500 watt DC supply.

Means a 800 VA tranny for continuous operation.

...... Phil

thank you for at least warning me.

dont be dense.

NT

** MASSIVE GOOGLE FUCKWIT ALERT ~!!~

** Uranium is translucent compared to this asinine POS.

........ Phil

In message , dated Sun, 13 Aug 2006, snipped-for-privacy@care2.com writes

You've allowed for all those and forgotten transformer impedance (usually expressed as 'regulation', when it's the opposite). For this sort of transformer, you can expect the open circuit voltage to be 5% higher than the full-load voltage.

Again, that's the voltage you would get with no output current. Calculating what you get with a given output current is difficult, but you can get an approximate value by assuming that the diodes conduct for (these days, with BIG filter caps) a quarter of a cycle. It's difficult to explain the calculation without a diagram and I don't have time to do it at the moment.

If you were 'younger' 30 or more years ago, and operated your transformers outside of an enclosure, you got away with it. Modern transformers, with those big filter caps (resulting in higher r.m.s. diode current), mean higher temperature rises, and you won't get away with it now. Diodes now have lower losses, so they generally don't overheat.

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK

so how do you get +/- 50V from a single 47V secondary

You can call it two half-wave rectifiers but it's the same circuit as a voltage doubler, and it puts a common mode ripple on the power rails

Bye. Jasen

Kinda late but i was playing around with 2n3055's in the late 1960's. Also

2n4400's i think.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller

OK. You have used a "doorknob" power device. What the heck did it look like? Where can i find outline drawings? You are about the third person i have heard admit of their existence.

--
 JosephKK
 Gegen dummheit kampfen die Gotter Selbst, vergebens.  
  --Schiller

In message , dated Mon, 14 Aug 2006, jasen writes

What do you mean by 'common-mode ripple'?

--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
2006 is YMMVI- Your mileage may vary immensely.

John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK