Tweakers' Asylum

Posted by jad (A) on July 20, 2021 at 09:14:00

In Reply to: RE: How about for an SU2? posted by jad on July 20, 2021 at 08:34:43

Posted by Jon Risch on February 9, 2000 at 21:46:34
In Reply to: Re: to J. Risch concerning Balanced power posted by Michael Donahue on February 9, 2000 at 10:54:59:

The Signal SU-2 is nominally a step-up OR step-down transformer. It is due to the flexibility afforded by the dual windings on both what are called the Primary and Secondary that it can be used as a balanced isolation unit.
If you read and follow my wiring instructions in the note, you will find that I have what Signal calls the Secondary windings in parallel and they are being used as the input windings, while what Signal calls the Primary windings I have in series, and am using them as the output windings. This is what provides the balanced AC power, with the center tap.

See Batman's post for further explanation. If you can not understand how to wire the transformer given the instructions in the note and these further comments, I strongly recommend you seek aid to wire the unit, or you run the risk of damaging your equipment, or possibly hurting yourself. If the transformer is wired incorrectly, it is theoretically possible to achieve several thousand volts across certain windings.

Jon Risch

Posted by Batman on February 9, 2000 at 19:09:10
In Reply to: Re: to J. Risch concerning Balanced power posted by Michael Donahue on February 9, 2000 at 10:54:59:

You are correct, Jon calls for this transformer to be wired "backwards" ie. with the wall current connected to the secondary of the transformer. BUT note carefully, unlike what he calls out for the DU-2 transformer, in this design the two 240-volt windings are connected in PARALELL. That is, the two "0" taps are connected togther and the two "240" taps are connected together. On the other side of the transformer, the two 120-volt coils are connected in SERIES, that is with the "120" lead of one coil connected to the "0" lead of the other coil.
Looking at it another way, the two 240-volt coils each have twice the number of turns (2N) as each of the two 120 volt coils (1N). Since the voltage across a transformer is a function of the ratio of the number of primary turns to the number of secondary you end up with a transformer with a turns ratio of 1:1. This is because the paralelled 240 volt windings only count as 2N windings while the series secondaries become 2N (1N+1N). Since the ratio of the turns is 1:1 (2N:2N), the output voltage (across the entire secondary) will equal the input voltage.