The Aleph-X

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#1,241
UrSv,

From a same source quote:

>7) Can Acme transformers be reverse connected?

ACME dry type Distribution transformers can be reverse connected without a loss of KVA rating, but there are certain limitations. Transformers rated 1 KVA and larger single phase, 15 KVA and larger three phase can be reverse connected without any adverse affects or loss in KVA capacity. The reason for this limitation in KVA size is, the turns ratio is the same as the voltage ratio<

Just imagine your average toroidal transformer with two sets of secondaries which can be connected either in series or parallel, producing same power. I guess everybody accepts this assumption.

If the above quote is correct, you can reverse connect the transformer and use either parallel or series connection of secondary windings (which in my example become primaries) and the power stays the same. If it's correct for secondary windings, I don't see any reason why that wouldn't be true for primary windings as well.
😉
 
#1,242
Hi Fred,

I couldn't find any information on how the total available power was affected by using the transformer at half the normal input voltage on that link but other than that it is quite informative.

Peter,

Seems reasonable in some cases. However not that related to the question at hand I think.

I would be quite happy in being wrong in this case as it would extend the possible uses of transformers used in 115 V countries if the transformer was kindly equipped with dual primaries.

Maybe it is my limited knowledge of transformer stuf, but I still can't see how the transformer would provide the same power...

Hopefully somebody will come up with a reliable answer (more than mine which I thought was pretty good) which will explain it technically as well.

Meanwhile....I have found a heatsink, dusted off some IRFP140s and spun some new power resistors. Maybe I can return to topic and build myself an Aleph-X if reports are favourable..

/UrSv
 
#1,243

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#1,245
Re: Seems to be half when operated at half the voltage

Fred Dieckmann said:

Transform KVA ratings are referenced to the current draw by the secondary windings. Series coneection of the primary windings give half the voltage at the secondary. Copper losses actually conplicate this a bit more also.
Click to expand...

I talked to Plitron. They basicaly confirmed the above, with a twist. Power depends on the current capacity of the secondaries and the voltage. The gauge of the wire defines the current. If you connect primaries in series, and instead of supplying 240V, use 120V only, you will get half the voltage on secondaries. Because you can't increase the current capacity of the existing wire your effective power is actually halved because the voltage is halved. I can't believe they said that.:bawling: 😉
 
#1,248
"While it makes perfect sense, it complicates things for me"

Now that is a totally different issue but an unfortunate one at that.

Dig out some more heatsinks, and EVERYBODY knows you have them, and run it at nominal voltages?

Paulb (I think) said something about taking any config he could get be it single secondary, dual in parallell or dual in series to get what he wants...

Maybe the Aleph-X (and some of the Hiragas it seems) is a candidate for a "virtual" center tap. Run the transformer secondary (in parallell most likely) at nominal voltages creating a virtual ground by means of a resistive divider giving +/- half the original voltages). Possibly the current drawn by the output stage is symmetrical, causing symmetrical rail drops and the current drawn by the front-end small enough to be acceptable drawn through the virtual ground. That would mean that you could run it with the transformer in its full glory?

Then again, as Fred pointed out so nicely, my knowledge is limited. I am sure somebody with a higher limit, or none, can answer this question...

:blush:

/UrSv
 
#1,254
"If you use transformer designed for 120V with 240V arrangement you will get half the voltage on secondaries"

Peter,
Maybe you mean the other way around feed 120 to a 240 coil, if you do what you said bad things will happen, in air the v sec will double in iron the core will saturate.
 
#1,256
grataku said:
"If you use transformer designed for 120V with 240V arrangement you will get half the voltage on secondaries"

Peter,
Maybe you mean the other way around feed 120 to a 240 coil, if you do what you said bad things will happen, in air the v sec will double in iron the core will saturate.
Click to expand...

I meant connecting primaries in series, and instead of supplying 240V, using 120V only. My choice of words wasn't the best indeed.😉
 
#1,257
carpenter said:
The regulated supply circuit Nelson laid out in his article mentioned that it drops 4 volts off the top. If I use a 22/22v (400V/A) secondary source and filter it through an LC circuit, my final voltage would be a very clean 15.6/15.6 volts. This should work fine.
John
Click to expand...
What have you assumed / calculated the output voltage of the LC to be (= the input voltage to the regulator)? I think you could get by with lower transformer voltage, even with the LC and the regulator.
Are you using the power supply simulator software that has been mentioned around here?
 
#1,259
When V1, I1, N1 are primary and V2, I2, N2 are secondary,
V2/V1=I1/I2=N2/N1.
When N1 is double, I1 is half. This is to maintain the formula.
It could mean the power rating remains the same (or almost same, tho).
What do you think?
Click to expand...
Sorry, ignore the above. I would like to correct myself as follows.

If I assume the rate of magnetic flux change per turn is the same for primary and secondary, V2/V1=N2/N1. If N1 becomes double while V1 maintains the same, the V2 becomes half while N2 maintains the same. I however still think the power rating of the transformer could remain the same.

JH
 
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