Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old February 4th 17, 11:35 AM posted to sci.electronics.repair
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Default Transformer Question

Next time, try to think before replying.

Only a stupid idiot would connect primary and secondary in parallel.

What I was meaning is to disjoint the two half-windings and put them in
parallel ON EACH SIDE.


The insulation in that casen is 240/2=120V
(170V peak to peak).


I have designed hundreds of transformers in my life (certified UL EN
etc..) and also planar transformers !

I realized several transformers for EDF (the French Electricity
Corporation), all of them compliant.



Phil Allison a écrit :
Look165 is a top posting nut case & troll e:



Exact !! But for me it was obvious

Well...not completely exact :

What counts is the magnetic flux seen by the 2 windings ; Since they may
not be at the very same place is might not imply the same number of turns.


** More complete ******** for a complete bullocker.


Generally, these winding are executed (manually or automatically) by the
"2-wire in hand" method.



** Not in the case of the 240V-240V windings, only a lunatic would wind them as a bifilar pair and rely on the enamel alone.

BTW:

You have no ****ing clue about the insulation needed for a 1:1 isolation tranny - do you ??

****ing tenth wit top poster troll.




.... Phil





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Old February 4th 17, 01:01 PM posted to sci.electronics.repair
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Default Transformer Question

Look165 is a absolute ****ing IDIOT wrote:


Only a stupid idiot would connect primary and secondary in parallel.


** So must be one of your type.


What I was meaning is to disjoint the two half-windings and put them in
parallel ON EACH SIDE.



** Precisely what I was thinking you meant.


The insulation in that case is 240/2=120V
(170V peak to peak).


** But when wire is *SERIES* places 480V between adjacent enamelled wires.



I have designed hundreds of transformers in my life (certified UL EN
etc..) and also planar transformers !


** Then you need to be taken out an ****ING SHOT DEAD !!

You ****ing tenth wit wog top poster.

Go **** yourself - you damn LIAR




..... Phil
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Old February 4th 17, 02:21 PM posted to sci.electronics.repair
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Posts: 353
Default Transformer Question

On Thu, 02 Feb 2017 14:26:41 -0600, wrote:

I was looking at the commercial isolation transformers and they are very
costly, so I decided to build my own. After all, all they are is a
transformer with a power cord on the primary and an outlet (and fuse) on
the secondary. And I already have an enclosure to put it in.

I'm looking at a bare transformer to use as an 120v isolation
Transformer. (120v in, 120v out). The transformer primary is 480 / 240.
The secondary is 240 / 120.

This is for single phase 60 cycle AC. (U.S. power).

Will it work if I connect the 240 lugs on the primary to 120 volts, and
use the 240 lugs on the secondary to obtain 120 volts.
Electrically, this makes sense, but I am not 100% sure, so I thought I'd
ask.

Also, this Transformer is rated at 750 va.


The 750VA rating applies to the part at it's label voltages. If there
is a dual primary - two windings which, connected in series, will
support 480V and which, connected in parallel will support 240V, then
a primary current of 1.5A is expected in each winding under rated
operation.

Reducing the voltage does not change the current capability of these
windings. If you halve the applied voltage, you halve the throughput
power rating, in this case, to 375VA.

A less efficient winding method, with a single tapped winding, will
use different gauge wire for the 240V section of the winding.

The same considerations apply to the secondaries.

Wired as 240in to 240out will produce a 1:1 isolation transformer.

RL
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Old February 4th 17, 02:25 PM posted to sci.electronics.repair
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Default Transformer Question

On Fri, 3 Feb 2017 22:44:16 -0800 (PST), Phil Allison
wrote:

Look165 wrote:


Just unlink the two winding by cutting at the middle point which is the
common one (it makes 4 separate windins).


** OK - so 240 & 240 plus 120 & 120.


Then put them in parallel at primary and secondary (and in phase !).



** Nah, that makes a 240 to 120 step down.

But only if the parallel pairs of windings have the *exact* same number of turns.

If not, you get major overheating.



.... Phil


Windings with the same label voltage will have the same turns. This is
checked automatically/electronically during fab. Unbalanced turn coils
are discarded/scrapped.

RL


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