[sdiy] basic transformer question (delurk)

[Scott Gravenhorst]

If you are unable to get a data sheet, you can easily check
for proper phasing.  With the transformer completely out of
circuit, connect the secondary windings to form that center
tap as you believe they should be (you have a 50/50 chance of
getting right/wrong).  Leave the other two secondary leads
open - only connect them to an AC volt meter capable of
reading more than 36 volts.  Apply mains power to the primary
and read the meter.  If the meter reads near zero, you have
the windings phased wrong.  If the meter reads about 36 volts
(probably a bit more since the transformer will have no load)
then the windings are correctly phased as you have them
connected.  You will not damage the transformer doing this,
even if the windings are incorrectly phased.  Just fix that
and measure again.

Above all, use due and proper caution when playing with mains
power.


Harry Bissell Jr <harrybissell at prodigy.net> wrote:
>It is EXTREMELY important to get the phase of the
>windings correct as well.  I would agree that wiring
>one 0V terminal to one 18V terminal and using that as
>the center tap is probably correct... but check the
>maunfacturer's data sheet if in doubt.
>
>H^) harry
>
>
>--- Fredrik Carlqvist <ifrc at iar.se> wrote:
>
>> 
>> 2) is the way to go.
>> 
>> Fredrik C
>> 
>> 
>> -----Original Message-----
>> From: owner-synth-diy at dropmix.xs4all.nl
>> [mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf
>> Of ac
>> Sent: Wednesday, October 27, 2004 23:57
>> To: synth-diy at dropmix.xs4all.nl
>> Subject: [sdiy] basic transformer question (delurk)
>> 
>> Hi,
>> 
>> Building my first PSU and have a really basic
>> question.
>> 
>> My circuit obviously requires 18/0/18 from the
>> transformer (it's a +/-15
>> PSU).
>> 
>> The 2nd windings on my transformer or labelled as 0
>> 18 0 18.
>> 
>> ie there is no center tap as such??
>> 
>> So do i wire it in series or parallel?
>> 
>> 1) join the two 0v outputs and use each of the 18s
>> 
>> or
>> 
>> 2) join the central 18 & 0 and us the outside 0 & 18
>> to the PSU PCB.
>> 
>> This is really dumb, i know. And dump questions and
>> mains voltage are
>> not a good combination!
>> 
>> Any help appreciated.
>> 
>> ac
>> 
>> PS sorry if this comes through more than once - had
>> a few subscription
>> / posting problems.
>> 
>> 
>

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