Balanced Power

[caffeinator]

Soooo....moving on to phasing, if I may.  The transformer I want to use to try this out is a Hammond 182T60.  It has two primaries and two secondaries.  I know what to do on the primary side.  My question is with respect to the secondaries - do I tie them together in or out of phase, or, more to the point, do I connect dotted terminals together, or not together?

[Grainger49]

The secondaries should be connected in series.  Done the wrong way they subtract.  So, blue and gray tied together, the output voltage off of red and yellow.  That is undoted of one winding tied to the doted of the other winding.  That is additive.

[Paul Joppa]

There is a diagram in the data sheet:

http://www.hammondmfg.com/pdf/182%20Insert.pdf

Note that this transformer will slightly increase the voltage; at full rated current it adds 3 volts (117v primary, 120vCT secondary) while at lower current draw it will add more. The regulation is not specified, but it's probably no more than another 3v. Still, you may want to check your power line voltage to be sure it's not already high.

[Skip Pack]

I am presently using a dedicated 240 VAC outlet with two stepdown transfomers to give 120 VAC for my system.
I have done this for a number of years in two locations and like the results. When I build things I use the DPST
switch as mentioned, and also fuse both hot leads. I'm more comfortable with protection on both sides. It seems
to me that your common mode rejection should be more complete (though hardly perfect) pulling at least
semi-balanced power from your panel.

Skip Pack

[4krow]

Then, I am to understand that you are stepping down each leg of the 220V(110V, each leg) to 60V? That seems to be balanced power to me.
 I used to run each leg of 220V to a mono block amp. For whatever reason, it sounded better.

[Skip Pack]

> Then, I am to understand that you are stepping down each leg of the 220V(110V, each leg) to 60V?

Yes, that's correct. My voltages here (80 miles south of San Francisco) tend to run around 250/125 at the
outlet. They sure seem to have crept up over the years.

Skip

[Grainger49]

Line voltage is increased because it lowers the current.  Increasing the voltage doesn't cause transmission lines to heat up, but increased current surely does.

[4krow]

I had the same problem when I lived 30 miles out of Flagstaff. About 127V, and that was within one volt of 'good enough'. It screwed with everything, and so I bought two transformers with multiple taps that were activated by the voltage being sensed as too low or high. Tripplite makes them, but they are not perfect, and got a pretty good workout where I lived.

[Grainger49]

There are things called "constant voltage transformers."  They include a lot of reactance in the form of capacitors.  They will put out 120V from 90V to 150V input.  They are not cheap, they are an industrial device.

[Paul Joppa]

I've seen the multi-tap ones as well. The 5v steps can make havoc with some equipment.

I've also seen a very cool General Radio servo motor driven variac. Fun to watch it hunting for the right voltage ...

Grainger, those reactive ones put out a nasty waveform. And IIRC lots of magnetic-field noise as well.

[Grainger49]

We used them to power Modicon and A-B PLCs.  Both were very sensitive to voltage problems.