The AM Forum

I have a powerstat 1226 autotransformer
I am feeding in 120 volts ac and as i turn it up im getting over 200 volts ac out.
Is that normal?

No,  make sure you have it connected correctly.  I would have to look up that model number to see what type it is.  Normally you would not get that much increase in voltage.

Ok can you please do that its a 1226  ser 8259

It's not a standard type powerstat.  I'll see if I can find it in the catalog, may take 15-20 minutes.  The terminal board connections are not that clear as to how to hook it up.

Fred

ok thanks

This accepts either 115 or 230V input.

Its output is 0-270V when the right voltage is applied to the right input.

If you want 0-135V output, feed the 120VAC into the 230V input.

The current rating will apply. 9A I believe.

If the unit's good, this should solve the issue.

Could not find anything on that 1226 type.  It may have been a special, not a regular catalog model.  Never saw one labeled with a dual voltage.  Goggle is the next place to look.  I'll look and see if anything comes up.

thanks it worked

Thanks Patrick,  

That's what I thought it was, a dual input voltage type.  Your terminal board and label is a lot more clearly marked.  The one that the OP pictured is not that clear.

I think that if you connect it to 115v it will give output voltage all the way to 270v.  The 115v terminal must be half way between the common and the 230v terminal.  The output wiper will run to the far end of the winding yielding the 270v output.  Does not look like there is a terminal connected at the high end of the winding, so the unit can only be used in the step-up mode.

The way to use it on 115v and yielding only 135v is to connect 115v to the 230v terminal.

So, connect the 115v line to the common and the 230v terminal and the output will be only around 0v-135v.  Of course the normal line voltage is more like 125v so the output would probably be 0v-148v.

Fred

true the higher voltage for today's line. I only knew because I have some 13KVA ones with multiple input voltages. The big ones do not seem to have changed from the 'old' appearance and are in the more recent catalogs. That 1226 one is probably in an older catalog before 1958. The corresponding schematic is below for the 13kva model.

The nice thing about these is that with the thing being an autotransformer, the input taps can be used to get 230V@4.5A from 115V@9A, or 115V@9A from 230V@4.5A. Meaning that no part of the winding can do more than the 9A rating.

A possible example is to use the unit on 230V as a plate transformer variac and run the final bias or filament transformer from the 115V tap which ought remain fairly constant.

Very nice part there.

Got it at a hamfest for 25 dollars lol

haha what a deal! Last owner probably didn't figure it out!