Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

"Mark Fortune" wrote in message
...
Greetings to the collective.

For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50) and
deliver up to 5amps of current. if my estimates are right i'll need a
600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had
a look at some transformers in this range, and they're a little out of my
price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Not really worth the effort, IMHO. However, take a look at All Electronics,
Hosfelt Electronics, MCM Electronics. There are others also. They have over
run surplus trannys with really good prices. The other alternative is try to
find an old high power am fm receiver which is kaput and not worth fixing.
They have a transformer with the approximate outputs you seek. You're right,
if you have the time, building your own power supply is fun and saves lots
of loot.
regards,
Tom

On Tue, 8 Aug 2006 15:01:26 -0400, "t.hoehler"
wrote:


"Mark Fortune" wrote in message
.. .
Greetings to the collective.

For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50) and
deliver up to 5amps of current. if my estimates are right i'll need a
600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had
a look at some transformers in this range, and they're a little out of my
price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Not really worth the effort, IMHO. However, take a look at All Electronics,
Hosfelt Electronics, MCM Electronics. There are others also. They have over
run surplus trannys with really good prices. The other alternative is try to
find an old high power am fm receiver which is kaput and not worth fixing.
They have a transformer with the approximate outputs you seek. You're right,
if you have the time, building your own power supply is fun and saves lots
of loot.
regards,
Tom



I had 3 toroids made by Tortran a couple years ago for a homemade
audio amp, they where very reasonable. I recommend you tell them to
give you a non-thermo protected primary.

In message , dated Tue,
8 Aug 2006, t.hoehler writes

Not really worth the effort, IMHO. However, take a look at All
Electronics, Hosfelt Electronics, MCM Electronics.

A bit difficult for a person based in UK, perhaps. And 60-0-60 V at
around 9 A is a BIG receiver or amplifier. Around 300 W/channel.
--
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

On Tue, 8 Aug 2006 20:51:44 +0100, John Woodgate
wrote:

In message , dated Tue,
8 Aug 2006, t.hoehler writes

Not really worth the effort, IMHO. However, take a look at All
Electronics, Hosfelt Electronics, MCM Electronics.

A bit difficult for a person based in UK, perhaps. And 60-0-60 V at
around 9 A is a BIG receiver or amplifier. Around 300 W/channel.

Sounds about right.

Years ago I had a neighbor kid who needed tutoring in Algebra.

I couldn't get him really interested until I sweetened the pie by
offering to help him build a 400W guitar amplifier IF he got an "A" in
Algebra.

He did get the "A".

We built this beautiful thing (in 1975) that was so heavy that it took
two people to carry it, and I had to use fans on the heat-sinks ;-)

Put out 400W RMS into 4 x 16 ohm speakers in parallel.

For my effort his father, President of Anthony Pools, built me a
swimming pool at a bargain price.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim



I couldn't get him really interested until I sweetened the pie by
offering to help him build a 400W guitar amplifier IF he got an "A" in
Algebra.

He did get the "A".

We built this beautiful thing (in 1975) that was so heavy that it took
two people to carry it, and I had to use fans on the heat-sinks ;-)

Put out 400W RMS into 4 x 16 ohm speakers in parallel.

On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)"
wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim

[snip]

I'm trying to remember what semiconductors I used. But, IIRC,
2N3055's *were* available around that time.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

RST Engineering (jw) wrote:

What primitive semiconductors did you use in the output stage, or was it a
toob device? Did we have 2N3055s in '75? I don't memember.

Jim



I couldn't get him really interested until I sweetened the pie by
offering to help him build a 400W guitar amplifier IF he got an "A" in
Algebra.

He did get the "A".

We built this beautiful thing (in 1975) that was so heavy that it took
two people to carry it, and I had to use fans on the heat-sinks ;-)

Put out 400W RMS into 4 x 16 ohm speakers in parallel.

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.Â*Â*
--Schiller

On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

By the time you have bought the core, be it toroid or E I lams, bought the
bobbin (if you use E I) bought two lots of wire, insulating fabric tape etc etc
etc., you may as well go and buy the right thing.

We make our own up to 3kVA, and we have all the bobbins, wire, varnish, tapes
etc., but before you ask, we don't do one-offs. Most of ours are specials that
we have designed by an outside consultant. Above 3kVA we go outside for them as
it isn't worth keeping all the steel strip, special wire and bigger winders,
varnish dip etc etc.

We have a pair of winding machines plus a hand winder which we can wind up to
3mm copper wire or small rectangular tape.

You may have to look around for what you want, but I promise you it will save
you a lot of time and trouble.

Peter
--
Peter & Rita Forbes
Email:
Web: http://www.oldengine.org/members/diesel

On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune
wrote:

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well.

No, it won't :-)
Your math is right. But what do you expect if you decide to draw
1 Volt at 5 amps from that beast ?
Who / what is going to dissipate the 600 - 5 = 595 VA for you ?

Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.

Here's your advice: don't even think of starting at 600 VA if you
want to roll your first transformer :-)


--
Kind regards,
Gerard Bok

Mark Fortune wrote in
:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

By a lot of cheap toroidals on eBay, 5A at some low voltage that doesn't
sell well. Outputs in series, inputs in parallel. Switch-select to get
coarse adjust, variable regulate over one output's voltage range to get any
voltage over a large range with little loss.

Lostgallifreyan wrote:
By a lot of cheap toroidals on eBay, 5A at some low voltage that doesn't
sell well.

I have to agree with the sentiment 100%. Surplus transformers are
always going to be cheaper than custom-built :-). Most oddball
transformers on E-bay sell for pennies on the dollar (actually most
don't sell at all!)

And construction and mounting-wise, a lot of small transformers are way
easier to deal with than one mammoth one. Above a very small number of
VA you start building the case and mounting reinforcements around the
transformer anyway :-).

Tim.

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

I would recommend reading up from every source. I have built torroids
using the winding which was orginally a variac. These were 110 volt
units. You automatically have a primary so all you need to do is wind
the secondaries on top. I have also done the other type of transformer,
schelacing.the iron plates. I would also recomend what others have, buy
surplus on the market. Combine transformers if you can't find them.

greg

On Tue, 08 Aug 2006 13:21:34 -0700, zekor wrote:
Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

I would recommend reading up from every source. I have built torroids
using the winding which was orginally a variac. These were 110 volt
units. You automatically have a primary so all you need to do is wind
the secondaries on top. I have also done the other type of transformer,
schelacing.the iron plates. I would also recomend what others have, buy
surplus on the market. Combine transformers if you can't find them.


I used to work for a battery charger manufacturer who made their own
transformers. They had a machine to stack the lams, alternating, of course,
and a big machine to spin the bobbin while the guy hand-wound the windings
on it. Then, when it was all stacked, they'd whack it to make sure all of
the lams were as tight as they could get them, bolt it up, hypot it, and
then bake them and dip them in hot varnish.

BTW, I don't think there are many USENETizens who would consider
themselves part of any "collective" - that's the Borg. =:-O

Good Luck!
Rich

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need

Do you have lots of time and money and power transistors to blow?

It's not too hard to build a power supply to your specs. It's a lot
harder to build one that will have a MTTF of a week or more. Are you
sure you can design a power supply that can survive the accidental
short circuit, reverse polarity across a car battery, static
discharges, inductive kicks, thermal cycles, and all the things that
bench power supplies have to tolerate?

In my experience, bench power supplies blow out about once a year.
Blown pass transistors, driver transistors, yuck.

You might consider just souping-up a PC power supply. Put a LM350 and
a foldback current limiter, switchable to the +5 and +12v outputs. Add
a hefty diode and low ESR capacitor to voltage-double the 12 volts to
give you a 24VC source. You can even add a pot where the
voltage-sensing wire senses the +3.3 at the motherboard end to get a
variable voltage power supply. And the PS specs require over-current
and foldback protection on all PC power supplies.

Put two in series (with careful separation of the grounds) and you're
up to+48 volts at many man y amps, at very low cost and weight. For
example, MPJA has nice brand new 180 watt supplies for $8.95 !!!

"Ancient_Hacker" wrote in
oups.com:

In my experience, bench power supplies blow out about once a year.
Blown pass transistors, driver transistors, yuck.


Therein lies another nice thought. Lots of people use bench supplies, but
not everyone who does knows how to repair them. So if you find a decent one
broken you might buy it for peanuts and get it working. If you do, you'll
have learned a bit, and saved a lot.

I would look at cheap battery chargers.

Note that you can put the primaries in parallel and the secondaries in
series to get a higher output voltage by using multiple transformers. Check
phasing if you do this.

"Mark Fortune" wrote in message
...
For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

So......

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

**** man! Switch that ****!

Nope, nothing else I can say without profanity.

SMPS, use a range of supplies, or just go SOL.

I mean, are you really planning on water cooling the maximum 600W you'll
dissipate? Heatsinks that size can get pricey. Don't say it won't happen
(the full dissipation).

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

In article ,
Mark Fortune wrote:
Is this even a feasable project to undertake (moreso on the money side
than timewise). Any other advice also greatly appreciated.

Put a search in Ebay and store that page. Keep looking - odd and large
transformers come up often, and go for quite reasonable prices. But what
you want (roughly) is common on large audio power amps, so shouldn't be
difficult to find.

Because of economies of scale buying the materials needed to make one will
cost you much more than a factory - and that's without the time and
difficulty involved.

--
*Don't worry; it only seems kinky the first time.*

Dave Plowman London SW
To e-mail, change noise into sound.

Do you need both + and - power at the same time? If not, just have 0-50V
would save you half the power.
If you need to use 1V at 5A, your power supply would become pretty
inefficient (supplying 5W and wasting 300W). Are you planning to fan cool
it? If not you need a huge heat sink.

If you use a switching design, it would be a lot more efficient.


"Mark Fortune" wrote in message
...
Greetings to the collective.

For my next project I want to build a bench power supply and do away with
this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50) and
deliver up to 5amps of current. if my estimates are right i'll need a
600va+ (100v * 5a + overhead) transformer to do the job well. Now i've had
a look at some transformers in this range, and they're a little out of my
price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is this
even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

peter wrote:
Do you need both + and - power at the same time? If not, just have 0-50V
would save you half the power.

I would need the option of both +v and -v in respect to ground, but only
sometimes at the same time (ie when testing audio circuits, but not when
doing logic circuits) if I switched one of the secondary windings off...
would I still be saving half the power?

If you need to use 1V at 5A, your power supply would become pretty
inefficient (supplying 5W and wasting 300W). Are you planning to fan cool
it? If not you need a huge heat sink.

Wastage is becoming more apparent as I read more and more posts... and
am considering rethinking to a more energy efficient design now.

I was (originally) thinking big heatsink with some thermal controlled
fans screwed on.


If you use a switching design, it would be a lot more efficient.


switching psus I know nothing about, but think I will research this. Any
good places to start (apart from the obvious google)?

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Get a copy of the 1980 book:
Practical Transformer Design Handbook
Eric Lowdon
Howard W. Sams & Co. book publisher
ISBN: 0-672-21657-4

On Tue, 08 Aug 2006 19:20:01 +0100, Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A


Well, it's theoretically possible to build a transformer from scratch,
BUT! You have to make a bobbin, find a lamination vendor that will sell
you only a few hundred lams, assemble the damn thing, hypot it, and
test it, to determine that you didn't get the lams tight enough so your
leakage inductance is unacceptable, redo it, redo the windings, interleave
the lams again, whack it a few times, pot it - - -

After about two weeks of this crap, you might want to go check surplus
dealers - they usually have surprisingly good bargains on transformere -
sometimes, you can buy them by the pound.

Good Luck!
Rich

Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

Does nobody knows howto calculate transformers anymore?

this will be a 600Watt transformer

you will need iron of 150mm EEE and III (a standard dimension)
a form of 50x54mm

primary:
use 1.35mm diameter wire
roll 377 spirals

secondary:
use wire of 1.77mm diameter (if this does not exist, get the after next in
diameter)
weld first out line (60v)
roll 104 spirals
weld second out line (0v)
roll 104 spirals
weld third out line (60v)


put the irons one by one always alternate positions
tight as much as you can the irons
dive it into hot varnish and let it dry

this is just the transformer, i guess you will also want to pass AC to DC
and maybe a voltage regulator controlled by a variable resistor, but that
is another story


regards
ArameFarpado

Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark


Look for a surplus transformer, you won't save any money trying to build
one yourself.

That's a BIG supply to be using a linear regulator for, I suggest
looking at some of the switcher IC's available now days, National
Semiconductor makes a series called Simple Switchers which are FAR
easier to work with than designing a switcher from scratch and they have
HV versions which are good to 80V or so.

In article ,
Mark Fortune wrote:

Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

Look for a blown-out 200-400 watt audio amplifier (or receiver) at a
garage sale. The transformer you'll find in it will be pretty close to
what you want. The amp will also include a lot of other very useful
items such as big heat sinks, and so on.

Isaac

u know ...if u really wish to "learn" ...why dont you design yourself a
50A, 0-50V continuously variable SMPS ....capable of operating in both
CV and CC modes.

(i know what some ppl are going to say ....he wants to learn ...not
repent)

In article .com, "sparc" wrote:
u know ...if u really wish to "learn" ...why dont you design yourself a
50A, 0-50V continuously variable SMPS ....capable of operating in both
CV and CC modes.

(i know what some ppl are going to say ....he wants to learn ...not
repent)



I have a HP 6268B here with a bad transformer. I didn't even think of rebuilding the transformer.
Well it did do 0-40 volts at 0-30 amps. I just recently got the idea to buy another used transformer
at some reduce specs to install in the beast. Hmmmm.

greg

sparc wrote:
u know ...if u really wish to "learn" ...why dont you design yourself a
50A, 0-50V continuously variable SMPS ....capable of operating in both
CV and CC modes.

(i know what some ppl are going to say ....he wants to learn ...not
repent)


Given the replies i've had on this, it seems the more sensible way of
going about it. Whilst i'm sure I will enjoy with experimenting with
transformers in the future, building a power transformer - specifically
the beast i'm after does seem to be costly and time consuming going by
the responses i've had on this thread, and is unlikely to work (first
time around anyway), where in contrast I could just pick up old/broken
equipment at the local car boot sale for under a fiver. I've had a
little read on (very basic concepts of) switching mode power supplies,
and this does seem to way to go in terms of efficiency and size.

So yes, forgive me for my sins, I repent!

Thanks to all those that offered their advice however, it's been
insightful to me, and I certainly wont give up the opportunity to build
my own transformers in future... just not on such a power crazed level
where there are better solutions.

Regards,
Mark

"Mark Fortune" wrote in message
...
sparc wrote:
u know ...if u really wish to "learn" ...why dont you design yourself a
50A, 0-50V continuously variable SMPS ....capable of operating in both
CV and CC modes.

(i know what some ppl are going to say ....he wants to learn ...not
repent)


Given the replies i've had on this, it seems the more sensible way of
going about it. Whilst i'm sure I will enjoy with experimenting with
transformers in the future, building a power transformer - specifically
the beast i'm after does seem to be costly and time consuming going by the
responses i've had on this thread, and is unlikely to work (first time
around anyway), where in contrast I could just pick up old/broken
equipment at the local car boot sale for under a fiver. I've had a little
read on (very basic concepts of) switching mode power supplies, and this
does seem to way to go in terms of efficiency and size.

So yes, forgive me for my sins, I repent!

Thanks to all those that offered their advice however, it's been
insightful to me, and I certainly wont give up the opportunity to build my
own transformers in future... just not on such a power crazed level where
there are better solutions.

Regards,
Mark

Also realize 50A at 50V is 2500 watts at 100% efficiency. If you are in the
USA, you will need a 220V power connection to do this.

David

David wrote:

"Mark Fortune" wrote in message
...

sparc wrote:

u know ...if u really wish to "learn" ...why dont you design yourself a
50A, 0-50V continuously variable SMPS ....capable of operating in both
CV and CC modes.


--------------8---------------8--------------------

So yes, forgive me for my sins, I repent!

Thanks to all those that offered their advice however, it's been
insightful to me, and I certainly wont give up the opportunity to
build my own transformers in future... just not on such a power crazed
level where there are better solutions.

Regards,
Mark


Also realize 50A at 50V is 2500 watts at 100% efficiency. If you are in
the USA, you will need a 220V power connection to do this.

David


Wow, pretty sure i'm not going to need 50A at any voltage... not sure
where that came from as originally I only wanted 10A. Incidently though,
im in the UK so we have 230V by default.

In article ,
"David" wrote:

"Mark Fortune" wrote in message
...
sparc wrote:
u know ...if u really wish to "learn" ...why dont you design yourself a
50A, 0-50V continuously variable SMPS ....capable of operating in both
CV and CC modes.

(i know what some ppl are going to say ....he wants to learn ...not
repent)


Given the replies i've had on this, it seems the more sensible way of
going about it. Whilst i'm sure I will enjoy with experimenting with
transformers in the future, building a power transformer - specifically
the beast i'm after does seem to be costly and time consuming going by the
responses i've had on this thread, and is unlikely to work (first time
around anyway), where in contrast I could just pick up old/broken
equipment at the local car boot sale for under a fiver. I've had a little
read on (very basic concepts of) switching mode power supplies, and this
does seem to way to go in terms of efficiency and size.

So yes, forgive me for my sins, I repent!

Thanks to all those that offered their advice however, it's been
insightful to me, and I certainly wont give up the opportunity to build my
own transformers in future... just not on such a power crazed level where
there are better solutions.

Regards,
Mark

Also realize 50A at 50V is 2500 watts at 100% efficiency. If you are in the
USA, you will need a 220V power connection to do this.

Not to mention the heatsinks it'll take when you want to deliver, say,
12 volts at anywhere near that 50 Amps. Hint: Plan on a fan and wheels.

Isaac

In article ,
Mark Fortune wrote:
Thanks to all those that offered their advice however, it's been
insightful to me, and I certainly wont give up the opportunity to build
my own transformers in future... just not on such a power crazed level
where there are better solutions.

I'd also query the need for such a large bench top supply - unless you're
regularly repairing or building things like power amps.

--
*The man who fell into an upholstery machine is fully recovered*

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:
In article ,
Mark Fortune wrote:

Thanks to all those that offered their advice however, it's been
insightful to me, and I certainly wont give up the opportunity to build
my own transformers in future... just not on such a power crazed level
where there are better solutions.


I'd also query the need for such a large bench top supply - unless you're
regularly repairing or building things like power amps.


aha, you've discovered one of my planned future hobbies
any money in it though?

I ran across info on rectifier design up through filtering (but not
regulation) at:
http://www.ieeta.pt/~alex/docs/Appli...20Handbook.pdf
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--

On Fri, 11 Aug 2006 12:30:35 -0500, Bud--
wrote:

I ran across info on rectifier design up through filtering (but not
regulation) at:
http://www.ieeta.pt/~alex/docs/Appli...20Handbook.pdf
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.


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 Voice480)460-2350 | |
| E-mail Address at Website Fax480)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, Bud-- writes
I ran across info on rectifier design up through filtering (but not
regulation) at:
http://www.ieeta.pt/~alex/docs/Appli...20Applications
%20Handbook.pdf

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

Bud-- wrote:

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

http://www.ieeta.pt/~alex/docs/Appli...20Handbook.pdf
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 took a look at the ieeta handbook. Yipee, this is something i want. You
are right about the heavy physics, not for everybody. Thanks

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

You want 600 va ? But that means 90% effeciency !
That means you must use switch mode .

You must choose an ungapped ferrite core with 2000 or more MU ,

it will need litz wire on output ( simply use smaller wire and mo
strands ) .
Tiny cores will easy do 600 watts .
MJE13005's are the most popular but the Cxxxx ( 2SCxxxx)
equivalents are seen more cause all are built in China .

You will see all switch mode pow supplies changing to single
drive , for they are just as eff as push pull , and cheaper .
Thery self oscillate ! Control circuit simply pulls down the Base
of bipolar Xisistor to adj output voltage .
It is a myth that more power can be sent to output using push pull !
All low end switch mode PS are using single transistor and if you
measure
the Xformer and other parts , SURPRISE , it is same size and cheaper
to build and its also an easier circuit to control ! Simpler parts .
You still need a volt ref and Opto and a LM393 to sense current .

The myth started when they said the dead time would waste time
but as we EE's know the dead time dont exist ! And we dont have to
control it as LM494 crowd must do !

Its a simplification made in heaven , no compromises al all .
You simply dbl up the Primary winding transistors !
Remember ! Transistors in class D dont worry about balancing !
If standard PCPS has push pull using 2 each C2335/or MJE13005
i simply put them in parallel ! Same power output !
Of course in dumpster diving , you will need to be clever on the
2ndaries to get same voltages

Dont be put off , this is so simple it should be used in school
to teach . You will be amased at how many parts are tossed out !


BTW Free OpSys for PDA . I'll buy a ARM Eval board (
www.littlechips.com)
and create a Forth like integrated OpSys , call it NewForth for now .
Wanna learn to do top System software ? Follow me .....



Mark Fortune wrote:
Greetings to the collective.

For my next project I want to build a bench power supply and do away
with this old switch mode AT computer PSU that i'm currently using.

The design I have in mind will be pretty beefy, giving a wide range of
fixed and variable output voltages (i'm thinking from -50v up to +50)
and deliver up to 5amps of current. if my estimates are right i'll need
a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've
had a look at some transformers in this range, and they're a little out
of my price range. so now i'm considering building my own.

The specifications I need are as follows:

primary: 0-230v @ 50Hz
Secondary: 60v-0-60v
secondary output current max: 5A

I have an intermediate understanding of transformers, but have never
actually built one, hence I am seeking advice from those with experience
in this field.
So where do I start? what type of core is best for this application? - I
have a friend who's blasting off that toroids are best, but i'd like a
second opinion, and what kind of wire to use for the primary and
secondaries? what are good safety practices regarding insulation? Is
this even a feasable project to undertake (moreso on the money side than
timewise). Any other advice also greatly appreciated.

regards,
Mark

werty wrote:

You want 600 va ? But that means 90% effeciency !
That means you must use switch mode .

You must choose an ungapped ferrite core with 2000 or more MU ,

it will need litz wire on output ( simply use smaller wire and mo
strands ) .
Tiny cores will easy do 600 watts .
MJE13005's are the most popular but the Cxxxx ( 2SCxxxx)
equivalents are seen more cause all are built in China .

You will see all switch mode pow supplies changing to single
drive , for they are just as eff as push pull , and cheaper .
Thery self oscillate ! Control circuit simply pulls down the Base
of bipolar Xisistor to adj output voltage .
It is a myth that more power can be sent to output using push pull !
All low end switch mode PS are using single transistor and if you
measure
the Xformer and other parts , SURPRISE , it is same size and cheaper
to build and its also an easier circuit to control ! Simpler parts .
You still need a volt ref and Opto and a LM393 to sense current .

The myth started when they said the dead time would waste time
but as we EE's know the dead time dont exist ! And we dont have to
control it as LM494 crowd must do !

Its a simplification made in heaven , no compromises al all .
You simply dbl up the Primary winding transistors !
Remember ! Transistors in class D dont worry about balancing !
If standard PCPS has push pull using 2 each C2335/or MJE13005
i simply put them in parallel ! Same power output !
Of course in dumpster diving , you will need to be clever on the
2ndaries to get same voltages

Dont be put off , this is so simple it should be used in school
to teach . You will be amased at how many parts are tossed out !


600VA thru litz wire?
no dc component on single ended drive? (-- copper losses)
cant get more power thru without the dc component?
News to me.


NT