[R-390] Isolation transformer questions

Wed, 5 Nov 2003 13:24:47 -0600

Bingo.  110 might be okay for some BA gear, but my TO's "new" 1L6 doesn't
like the input below 115VAC.

By the way, I got the following response from Signal about running the
primary on the 110V tap and the secondary on 104V:

	Dear Barry.

	Thank you for visiting our website.  
	Your input/output configuration would not caused any damages to
transformer (may shorten 	life slightly, but usually we recommend to
stay within 10% deviation range from nominal 	voltage.  Should you have
any further questions, please do not hesitate to contact us.

	Best Regards,
	Sergey Dubatov
	Design Engineer
	Signal Transformer Co
	Ph. 516-239-5777 x 173
	Fax 516-239-7208   
	[email protected]

Very fast response to my question!

Barry(III) - N4BUQ

-----Original Message-----
From: Barry Hauser [mailto:[email protected]]
Sent: Wednesday, November 05, 2003 12:19 PM
To: Scott, Barry (Clyde B); R390 (E-mail)
Subject: Re: [R-390] Isolation transformer questions

I dunno, Baaa... watch what you're doin' there.

The text on that page reads as follows:

"As shown on the schematic diagram the "DU" line is designed with dual
primaries and secondaries. All four windings are identically rated at
0/104/110/120 volts. This permits series or parallel connections on either
primary or secondary. Therefore, a nominal 110 to 110 volt, 220 to 220
volt,110 to 220 volt, or 220 to 110 volt transformer can be set up. The
winding taps permit intermediate series ratings such as 208, 214, or 230
volts. It is also possible to make auto-transformer connections by
connecting a primary group in series with a secondary group. Such nominal
ratings as 440 to 220 volts or 220 to 440 volts can be set up, in addition
to the standard ratings described above. A further advantage to
auto-transformer connection is the fact that the KVA rating of a particular
type is doubled.

It looks like it has a full complement of multi primary and multi secondary
taps.  Says it allows for "intermediate settings, such as 208, 214, or 230."
But I take that to mean that you can also do 104, 110, 120, or maybe even
mix 'n match the two sets of secondaries to get 110+120/2=115 -- which is
what you're asking, I guess.  They say you can do 214, for example, so it
would seem that you could do that.

Now they say you can make autotransformer connections by connecting a
primary group in series with a secondary group -- but (folks) correct me if
I'm wrong -- what they don't say is that if you make an autotransformer out
of it, it's no longer an isolation transformer.

If your line voltage is running something like 125-126, as it does here, I
would go with the 120/110 primary/secondary arrangement which would give you
about 115.  If it runs down to 110, then that might be OK as well -- unless
you swap that 1L6 back into your TO ;-).

Barry

----- Original Message -----
From: "Scott, Barry (Clyde B)" <[email protected]>
To: "R390 (E-mail)" <[email protected]>
Sent: Wednesday, November 05, 2003 9:31 AM
Subject: [R-390] Isolation transformer questions

> Thanks to a list member, I'm the proud owner of a very nice isolation
> transformer (Model DU-1 shown in the following page)
>
> http://www.belfuse.com/Data/DBObject/pgs28_29.pdf
>
> I'm wondering about connecting the secondaries.  Normally, I would connect
> both 120V secondaries in parallel yielding the full 9A capacity; however,
my
> line voltage is a bit higher than I'd like.  I know I could use one
> secondary and one of the other secondary windings to "buck" 6 or 10 volts,
> but that would limit the current to only 4.5A.
>
> My question is this: what would be the result of connecting the 120V
> secondary in parallel with the 110V secondary of the other winding?  Is
> there an "averaging" effect?  Will this damage the transformer?  I've
never
> thought about this before and wonder what will happen.
>
> Thanks in advance,
>
> Barry(III) - N4BUQ
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