transformers in parallel

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Do I have to worry about connecting the outputs "in phase", or does it
matter?

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

Thanks,

Michael

 

[Phil Allison]

<mrdarrett@gmail.com

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

** No.

Do I have to worry about connecting the outputs "in phase",

** Yes.


..... Phil

 

[Phil Allison]

<mrdarrett@gmail.com>

Without a scope, how could I make sure they're in phase?

** There all identical - right ?

Just wire each one the exact * SAME * way.

Jeez - what a dope !



........ Phil

 

[Peter Bennett]

On Fri, 28 Mar 2008 16:41:30 -0700 (PDT), mrdarrett@gmail.com wrote:

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Well, it's not a great idea, but should work - I'd prefer to get a
suitable transformer if possible.

Do I have to worry about connecting the outputs "in phase", or does it
matter?

Yes, definitely.

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

If I had to use multiple transformers, I think I'd prefer to use a
separate bridge rectifier on each one (then you don't have to worry
about the transformer phase), but you only need a single filter
capacitor bank. I would probably put a low-value resistor between
each rectifier output and the filter capacitor(s), in the hopes of
equalising the loading on the four transformers.

Thanks,

Michael

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[Jamie]

mrdarrett@gmail.com wrote:

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Do I have to worry about connecting the outputs "in phase", or does it
matter?

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

Thanks,

Michael
Putting the xformers together like that is fine how ever, make sure you

phase them correctly to not short each other.
As far as the bridges. You would be better off with a single bridged
rectifier that can handle the full load.


http://webpages.charter.net/jamie_5"

 

On Mar 28, 6:04 pm, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

mrdarr...@gmail.com wrote:
Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Do I have to worry about connecting the outputs "in phase", or does it
matter?

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

Thanks,

Michael

Putting the xformers together like that is fine how ever, make sure you
phase them correctly to not short each other.
As far as the bridges. You would be better off with a single bridged
rectifier that can handle the full load.

http://webpages.charter.net/jamie_5"

Without a scope, how could I make sure they're in phase? (Besides
doing the thermal test: if they get too hot, I know something's wired
backwards)

Michael

 

[Jamie]

mrdarrett@gmail.com wrote:

On Mar 28, 6:04 pm, Jamie
jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

mrdarr...@gmail.com wrote:

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Do I have to worry about connecting the outputs "in phase", or does it
matter?

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

Thanks,

Michael

Putting the xformers together like that is fine how ever, make sure you
phase them correctly to not short each other.
As far as the bridges. You would be better off with a single bridged
rectifier that can handle the full load.

http://webpages.charter.net/jamie_5"




Without a scope, how could I make sure they're in phase? (Besides
doing the thermal test: if they get too hot, I know something's wired
backwards)

Michael
use your volt meter.

connect all the primaries to gather in any order in
parallel.
then connect only one leg of each transformer of the
secondary side together. with a volt meter you should
not get any significant reading between the other 2 leads.
You will ether get a canceled reading between each other which
is what you want or, a double voltage reading which is not what
you want.
if you get the double reading, switch the leads on one xformers
secondary and wire the other 2 together.
repeat the same action with the rest treating the currently paired
xformers as one..


http://webpages.charter.net/jamie_5"

 

[Phil Allison]

"Peter Bennett"

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Well, it's not a great idea, but should work - I'd prefer to get a
suitable transformer if possible.

** The only disadvantage of using multiple identical AC supply
transformers is that * usually * it costs more and increases the weight
compared to a single unit.

If I had to use multiple transformers, I think I'd prefer to use a
separate bridge rectifier on each one (then you don't have to worry
about the transformer phase), but you only need a single filter
capacitor bank. I would probably put a low-value resistor between
each rectifier output and the filter capacitor(s), in the hopes of
equalising the loading on the four transformers.

** But the OP stated his transformers WERE identical !!!

So no need for additional parts that just WASTE power and money.

IME, mass produced transformers come out identical, the number of turns
used is automatically counted and is exact.

One only needs an AC meter to prove the point - by reading ZERO volts
when connected across two similar ( in phase) secondary windings joined at
one end.



....... Phil

 

On Mar 28, 4:17 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

mrdarr...@gmail.com

Without a scope, how could I make sure they're in phase?

** There all identical - right ?

Just wire each one the exact * SAME * way.

Jeez - what a dope !

....... Phil

Yes, they are identical - but the secondaries are just two wires of
the same color and it's not clear how they come out of the roll.
Hence it's possible to get them "mixed up".

Michael

 

On Mar 28, 4:44 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

"Peter Bennett"

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Well, it's not a great idea, but should work - I'd prefer to get a
suitable transformer if possible.

** The only disadvantage of using multiple identical AC supply
transformers is that * usually * it costs more and increases the weight
compared to a single unit.

In this particular instance, ordering a dozen surplus 24V transformers
is quite cheap. Much, much cheaper than buying one center-tapped 48V,
200VA transformer (which, ideally, is what I'd want).

If I had to use multiple transformers, I think I'd prefer to use a
separate bridge rectifier on each one (then you don't have to worry
about the transformer phase), but you only need a single filter
capacitor bank. I would probably put a low-value resistor between
each rectifier output and the filter capacitor(s), in the hopes of
equalising the loading on the four transformers.

** But the OP stated his transformers WERE identical !!!

So no need for additional parts that just WASTE power and money.

IME, mass produced transformers come out identical, the number of turns
used is automatically counted and is exact.

One only needs an AC meter to prove the point - by reading ZERO volts
when connected across two similar ( in phase) secondary windings joined at
one end.

...... Phil

k, sounds good.

I think I'll go with Peter's idea and just use one capacitor bank,
multiple bridge rectifiers.

Thanks,

Michael

 

[Phil Allison]

<mrdarrett@gmail.com>

Without a scope, how could I make sure they're in phase?

** There all identical - right ?

Just wire each one the exact * SAME * way.

Jeez - what a dope !



Yes, they are identical - but the secondaries are just two wires of
the same color and it's not clear how they come out of the roll.

** So they are NOT IDENTICAL after all - eh ??

Shit head.



....... Phil

 

[Phil Allison]

<mrdarrett@gmail.com>

I think I'll go with Peter's idea and just use one capacitor bank,
multiple bridge rectifiers.

** You are nothing but a fuckwit ASSHOLE !!

PISS OFF DOPE !!



....... Phil

 

[Phil Allison]

<mrdarrett@gmail.com>


** Go get fucked -


you vile, rude, ignorant genetic mental defective.





....... Phil

 

On Mar 28, 6:46 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

mrdarr...@gmail.com



Without a scope, how could I make sure they're in phase?

** There all identical - right ?

Just wire each one the exact * SAME * way.

Jeez - what a dope !

Yes, they are identical - but the secondaries are just two wires of
the same color and it's not clear how they come out of the roll.

** So they are NOT IDENTICAL after all - eh ??

Shit head.

...... Phil

You have interesting ideas about the word "identical".

I suppose the isotopic composition of the iron core could vary by a
few thousandths of a percent...

Michael

 

[HapticZ]

lots of cheap surplus switching supplys around!


<mrdarrett@gmail.com> wrote in message
news:5617e3c9-b9e9-42ec-80b8-c76d3b332631@d4g2000prg.googlegroups.com...

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Do I have to worry about connecting the outputs "in phase", or does it
matter?

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

Thanks,

Michael

 

[Paul E. Schoen]

"HapticZ" <hapticz@sbcglobal.net> wrote in message
news:ahjHj.3035$p24.1512@nlpi061.nbdc.sbc.com...

lots of cheap surplus switching supplys around!

That's the best way to get the voltage and current required for the OP's
amplifier supplies. Two 65 VA switchers would be a complete solution for
130 watts, and would cost $56 total, which includes all required primary
fusing, rectification, current limiting, and regulation.

The shipping would be a lot more for surplus transformers, and then you
have to add rectifiers, capacitors, and circuit protection components. If
you factor in even a little bit for your time, the cheap transformer
solution doesn't look so good.

Just a quick check on eBay came up with 124 hits, including 24V 6A Buy It
Now for $22:

http://cgi.ebay.com/24V-DC-6A-145W-Regulated-Switching-Power-Supply_W0QQitemZ350039954049QQihZ022QQcategoryZ58286QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Or a 200 watt dual output +/- 43V 2A switcher from an audio amp, current
bid $9.50:

http://cgi.ebay.com/200W-Switching-Power-Supply-Dual-43V-2A-Audio-Amp_W0QQitemZ150230269229QQihZ005QQcategoryZ36323QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Or buy it now for $21.50. Hell, I think I'll get one of these babies
myself. I just bid on it. Should come in handy when I make my experimental
amplifier.

I'd rather do things the easy way.

Paul

 

[Jamie]

mrdarrett@gmail.com wrote:

On Mar 28, 4:44 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

"Peter Bennett"


Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Well, it's not a great idea, but should work - I'd prefer to get a
suitable transformer if possible.

** The only disadvantage of using multiple identical AC supply
transformers is that * usually * it costs more and increases the weight
compared to a single unit.



In this particular instance, ordering a dozen surplus 24V transformers
is quite cheap. Much, much cheaper than buying one center-tapped 48V,
200VA transformer (which, ideally, is what I'd want).



If I had to use multiple transformers, I think I'd prefer to use a
separate bridge rectifier on each one (then you don't have to worry
about the transformer phase), but you only need a single filter
capacitor bank. I would probably put a low-value resistor between
each rectifier output and the filter capacitor(s), in the hopes of
equalising the loading on the four transformers.

** But the OP stated his transformers WERE identical !!!

So no need for additional parts that just WASTE power and money.

IME, mass produced transformers come out identical, the number of turns
used is automatically counted and is exact.

One only needs an AC meter to prove the point - by reading ZERO volts
when connected across two similar ( in phase) secondary windings joined at
one end.

...... Phil



k, sounds good.

I think I'll go with Peter's idea and just use one capacitor bank,
multiple bridge rectifiers.

Thanks,

Michael
Bad idea,,..

The diodes in the rectifier will not allow for even load distribution.
You may even have a bridge sitting there doing nothing while another is
doing all the work and over loading if self along with the single
Xformer it's connected to.
Please take good advise and combined all the xformers in parallel
into a single bridge rated for the combined load.

http://webpages.charter.net/jamie_5"

 

On Mar 29, 7:09 am, Jamie
<jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:

mrdarr...@gmail.com wrote:
On Mar 28, 4:44 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

"Peter Bennett"

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Well, it's not a great idea, but should work - I'd prefer to get a
suitable transformer if possible.

** The only disadvantage of using multiple identical AC supply
transformers is that * usually * it costs more and increases the weight
compared to a single unit.

In this particular instance, ordering a dozen surplus 24V transformers
is quite cheap. Much, much cheaper than buying one center-tapped 48V,
200VA transformer (which, ideally, is what I'd want).

If I had to use multiple transformers, I think I'd prefer to use a
separate bridge rectifier on each one (then you don't have to worry
about the transformer phase), but you only need a single filter
capacitor bank. I would probably put a low-value resistor between
each rectifier output and the filter capacitor(s), in the hopes of
equalising the loading on the four transformers.

** But the OP stated his transformers WERE identical !!!

So no need for additional parts that just WASTE power and money.

IME, mass produced transformers come out identical, the number of turns
used is automatically counted and is exact.

One only needs an AC meter to prove the point - by reading ZERO volts
when connected across two similar ( in phase) secondary windings joined at
one end.

...... Phil

k, sounds good.

I think I'll go with Peter's idea and just use one capacitor bank,
multiple bridge rectifiers.

Thanks,

Michael

Bad idea,,..
The diodes in the rectifier will not allow for even load distribution.
You may even have a bridge sitting there doing nothing while another is
doing all the work and over loading if self along with the single
Xformer it's connected to.
Please take good advise and combined all the xformers in parallel
into a single bridge rated for the combined load.

http://webpages.charter.net/jamie_5"

Ok, thanks.

(See? A good thing I asked. I had a hunch that just wiring the
primaries haphazardly would result in a problem...)

Michael

 

[Jon Slaughter]

<mrdarrett@gmail.com> wrote in message
news:5617e3c9-b9e9-42ec-80b8-c76d3b332631@d4g2000prg.googlegroups.com...

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Do I have to worry about connecting the outputs "in phase", or does it
matter?

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

I made a PS a few years back that did just this.

In fact you can parallel the primary side and put the secondary side in
series which is what I did. It gave me a +- polarity since they wernt CT.
(essentially doubled the secondary side windings) Of course it increased the
secondary side current through each by a factor of 2 which isn't necessarily
good but it works fine for my low power apps.

Putting both sides in parallel shouldn't have any effect but reduce the
power in each just like putting resistors in parallel. Putting both sides in
series gives the same ratio but the problem is the current in each will
increase and will probably exceed the rating(similar to resistors in
series).

i.e., in parallel you have same voltage across each and 1/nth the current.
In series you have 1/nth the voltage but the same current. (assuming ideal
and identical)

 

On 3ÔÂ29ČŐ, ÉĎÎç7Ęą41ˇÖ, mrdarr...@gmail.com wrote:

Let's say I've got a transformer, 110VAC primary, 24V secondary, 1A.

Let's say I've got 4 of them actually, same type, same manufacturer,
and want to wire them in parallel so I get 4A out, 24V.

Is this a bad idea?

Do I have to worry about connecting the outputs "in phase", or does it
matter?

I plan to rectify and filter the AC to get DC.

I suppose I could buy 4 bridge rectifiers and 4 filter caps to get the
DC out, but this gets expensive.

Thanks,

Michael

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