Center-tap Transformer Secondary Voltage confusion

[force of 1/2]

Hi All,

I have been looking at some cheap 2nd hand transformers on an auction site, and I am left a little confused about the voltage ratings on center-tapped secondaries.

Is there a clear and consistent way the secondary voltage is rated?

Exapmle:

Triad R-23J transformer with the spec printed on the end-bell:
250V @ 22mA Center Tap

I would assume this means that the transformer is 125v-0-125v

But the seller claims it is 250v-0-250v.


Any thoughts on this? Were there historically different ways the secondary rating was expressed?

Thanks!

regards,
John

 

[Julian RO]

But the seller claims it is 250v-0-250v.
John

That's right.

 

[6L6]

Hmmm... I’d suspect that to be 125-0-125, but measure and be sure.

 

[Mooly]

................I would assume this means that the transformer is 125v-0-125v

But the seller claims it is 250v-0-250v.

Tbh that is what I would have assumed as well. The first bit... 125-0-125

 

[Julian RO]

Here's an example of a connection.

But, I do not see the voltage for the filament of the rectifier lamp, 5V. Possible to be 125-125v.

 

[Mooly]

I would assume that to be 250 between red and red and 125 red (either) to yellow.

 

[force of 1/2]

I found an entry for an R-23a in an old Triad catalog. The HT secondary is listed as 125-0-125v @ 22mA.
My guess is the seller is not correct about 250-0-250.

So, does anyone know if there are ever cases when a transformer's rated secondary voltage is given as one half of the secondary winding (end to center) instead of the full winding (end to end)?

Or is it 'set in stone' that the Voltage will always be expressed in terms of the full winding?

Thanks!

 

[MorbidFractal]

I would assume that to be 250 between red and red and 125 red (either) to yellow.

Bit blurry but yes. Look at the winding below where it specifies 12.6/15.?V.

Your 250V is the only number so it's 125-CT-125

 

[Mooly]

.................

So, does anyone know if there are ever cases when a transformer's rated secondary voltage is given as one half of the secondary winding (end to center) instead of the full winding (end to end)?

Or is it 'set in stone' that the Voltage will always be expressed in terms of the full winding?

Thanks!

I don't if their is any standard but there should not be much doubt if you study the wording. If only one figure is given as here then you take it that is the full and total end to end voltage.

Had it been printed '250' in each section above and below the CT print then it would be taken to mean 500 in total with a tap in the centre. You would also then expect to see the 22ma printed twice as well.

Its blurry but does the 22ma say DC after it?