130VAC@40A to 130VAC-110VAC
Should a wind an autotransformer? What is the efficiency of autotransformer's?
Should a wind an autotransformer? What is the efficiency of autotransformer's?
Autotransformer efficiency is likely to be in the 95% range. Variacs are special adjustable autotransformers. Search for "variac" (also in e-bay 😀 ... not the forum member owning this nickname!!! 😀😀 )
At 40A? That's going to be one huge variac! 🙂
For that current and voltage, for safety and reliability, I'd be looking at getting a custom traffo made.
For that current and voltage, for safety and reliability, I'd be looking at getting a custom traffo made.
There are probably a lot of standard transformers suiting your needs. All that is required is 120V primaries and secondaries adding up to approx 20V and 40A. For example, two halogen lighting transformers with 120V primaries and dual 12V 20A secondaries may do the trick by connecting the secondaries in series with the primary (the output voltage may be a bit low, though). Toroids with 18V, 20V or 22V secondaries adding up to 800..1000VA would be fine too.
It may seem a bit couter-intuitive at first, but autotransformers work in another way. Think about it. Also, the VA rating of standard transformers no longer applies when you wire them as autotransformers, then what you have to consider is the current going through each winding.
Hi Eva,
could you re-phrase that about autotransformers and VA rating.
I think you are saying that the common winding from the lower voltage output (110Vac) to neutral does not need to be rated to the full current rating of the input and output.
If that is correct then only the top part linking 130Vac input to 110Vac output needs to be current rated to match the output current.
The final question then follows;
What is the VA rating of the lower winding?
VA=Vac sec / Vac pri * Iout * Vac input ?
Ak47
Irrespective, a dual secondary with 10Vac windings will give the option of 130, 120, 110Vac output from the 130Vac input.
And the other way as well.
Finally, 120Vac input with 110, 120, 130Vac output.
Now, if you were to add four 5Vac windings.
could you re-phrase that about autotransformers and VA rating.
I think you are saying that the common winding from the lower voltage output (110Vac) to neutral does not need to be rated to the full current rating of the input and output.
If that is correct then only the top part linking 130Vac input to 110Vac output needs to be current rated to match the output current.
The final question then follows;
What is the VA rating of the lower winding?
VA=Vac sec / Vac pri * Iout * Vac input ?
Ak47
Irrespective, a dual secondary with 10Vac windings will give the option of 130, 120, 110Vac output from the 130Vac input.
And the other way as well.
Finally, 120Vac input with 110, 120, 130Vac output.
Now, if you were to add four 5Vac windings.
A transformer with a 20 volt secondary @ 10 amp (200va) will work as an auto transformer having 130 V X 10 amps =1300VA..if the primary volts is 130.
pinkmouse said:
Main power regulation for all equipment, a little under 4000w peak if i have everything on. I blame the toobz 😀
Thats right, at most 1kw will be transformed since in the worst case scenario their will be a 20v passing through the iron.
So i need a 1kw sized transformer core and thick enough wire to handle 40 amps?
That would have been a big mistake!
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