"I converted my A75 amp intp Aleph X with primaries run in series"
Peter,
I don't know if that is such a great idea. That halves the VA rating by halving the A rating of the primary, right?
But if you must...
Brian,
what's the ballpark price for you 1kVA from VM? I think I may go with a quad 13V 800VA and dual 115V , just in case I'll ever move back to europe.
Peter,
I don't know if that is such a great idea. That halves the VA rating by halving the A rating of the primary, right?
But if you must...
Brian,
what's the ballpark price for you 1kVA from VM? I think I may go with a quad 13V 800VA and dual 115V , just in case I'll ever move back to europe.
hummmmmmm.........
Hi Peter,
I'm tri-amping and I'm fully horn loaded. You've seen the picture I posted regarding my huge chassis with the massive heatsinks, heat is not a problem. I think you made a pun "one cool chassis".
I've got the Aleph 30 schematics and have noted the slight changes in resistor value here and there. I've designed the pcb I'm using to accomodate the extra power resistors. I've also noted that I need three times the off board transistors/resistors. Now, if that darn pcb would just hurry up and get here.
I like your idea of using the smaller transformer to begin my first AX project. I'll probably end up doing just that. I've got a 500 V/A 16v-16v transformer that I've been experimenting with. With an LC filter and a 500 watt lightbulb load, it delivers a very steady 13 volts. It fluctuates 10 to 20 mV.
Thanks for all the suggestions,
John
Hi Peter,
I'm tri-amping and I'm fully horn loaded. You've seen the picture I posted regarding my huge chassis with the massive heatsinks, heat is not a problem. I think you made a pun "one cool chassis".
I've got the Aleph 30 schematics and have noted the slight changes in resistor value here and there. I've designed the pcb I'm using to accomodate the extra power resistors. I've also noted that I need three times the off board transistors/resistors. Now, if that darn pcb would just hurry up and get here.
I like your idea of using the smaller transformer to begin my first AX project. I'll probably end up doing just that. I've got a 500 V/A 16v-16v transformer that I've been experimenting with. With an LC filter and a 500 watt lightbulb load, it delivers a very steady 13 volts. It fluctuates 10 to 20 mV.
Thanks for all the suggestions,
John
grataku said:
I am not sure what it will cost, since I am having him just redo my Aleph 2 transformer. I will ask him when I go to pick it up.
--
Brian
An externally hosted image should be here but it was not working when we last tested it.
grataku said:
I'm not so sure about it. Although the A rating is halved, the voltage drop is over twice as many windings, so I assume the power should stay the same.
Brian, maybe you could ask the guy at VM how it really works, cause I'm curious myself.
Peter Daniel said:
I have always assumed that the power rating is the same. I will ask him tommorrow.
On a side note, I think that moderators should use this smilie when they have their moderator hat on:
An externally hosted image should be here but it was not working when we last tested it.
--
Brian
An externally hosted image should be here but it was not working when we last tested it.
paulb said:
Could you please explain how this would work? I would have assumed that the primary windings have been designed with a number of turns and a dc resistance to provide 2 identical 115 V primaries rated at half the total VA rating. Each of these primaries would provide half the VA drawn at the secondaries. If feeding the primaries in series with 115 V I would expect this to mean 57.5 V to each primary and consequently only half the total VA rating. If this wasn't the case wouldn't then connecting just one primary for 115 V operation be just as good as connecting both?
Let's hope Victoria Magnets proves me wrong but AFAIK you get half the VA rating.
/UrSv
As far as I understand, the power rating of the transformer is
referred to the secondary V and I. No?
JH
referred to the secondary V and I. No?
JH
Well there's two ratings really. Normally, a trannie would be rated as a whole component, used under the conditions specified. Once you do something non-standard with it, then you have to consider it a circuit made up of sub-components. VA rating is usually set by the core size, since there's only so much magnetic flux a given core can handle. This is pretty much fixed. But, the wire used for the windings will have a rating too, based on it's ability to handle the currents you put through it. If the wire is too small, it's ohmic resistance will be too high, and it will heat up more than an acceptable amount during operation. It will also cause power losses which translate directly to poorer performance from the trafo.
Anyway, in my recent conversations with John at VM (we're discussing group buy options for Aleph-X transformers), he indicated that their cores are oversized for what they're rated. I think you'll probably be ok operating one of their transformers this way. The best way to tell will just be to monitor the transformer temperature during use to see how it handles the change. You'll know if you're overstressing the trafo!
Anyway, in my recent conversations with John at VM (we're discussing group buy options for Aleph-X transformers), he indicated that their cores are oversized for what they're rated. I think you'll probably be ok operating one of their transformers this way. The best way to tell will just be to monitor the transformer temperature during use to see how it handles the change. You'll know if you're overstressing the trafo!
It's the losses in the core and windings that determine the VA rating. The core part should be okay but I think hifiZen is correct, you are also limited by the winding's current capability. Driving twice the current through a winding that it was designed for may be a problem, so I stand corrected.UrSv said:
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?
JH
PS. Of course, with the same core...
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?
JH
PS. Of course, with the same core...
I emailed John separately but thought I should post this in case I have a flaw somewhere. Assuming you want 4.5A per channel at +/- 15V. That's 135 watts.
If you wire up all 4 primaries in series (2 each from two transformers), you'll get 12.5 VAC on each of the secondaries. As long as you're drawing the same load from each transformer, and they are identical transformers, this should work fine. You're looking to get 135 watts of DC per channel, so my rule of thumb says you need 270VA of AC per channel. Even derating each transformer by a factor of 4 because we are running them off 1/4 the voltage (a conservative derating), gives you 250VA per transformer & therefore per channel.
John, you'd be wasting a lot of capability of the transformers, but I think this is definitely a way you could use them.
What do others think?
If you wire up all 4 primaries in series (2 each from two transformers), you'll get 12.5 VAC on each of the secondaries. As long as you're drawing the same load from each transformer, and they are identical transformers, this should work fine. You're looking to get 135 watts of DC per channel, so my rule of thumb says you need 270VA of AC per channel. Even derating each transformer by a factor of 4 because we are running them off 1/4 the voltage (a conservative derating), gives you 250VA per transformer & therefore per channel.
John, you'd be wasting a lot of capability of the transformers, but I think this is definitely a way you could use them.
What do others think?
Who is correct? I think I was actually underestimating the problem.
The trafo that comes with say 2 115v primaries is meant to be operated with the windings in parallel at 115 V or at 230 in series. Under normal circumstances the manifacturer sizes the Xsection of the primary wire based on that assumption.
Iron core and losses don't factor into this at all because the size of the core is determined independently for the nominal VA rating.
The primary is going to have twice the resistance it should have and is going to be operated.
Say you have 2 amps going around in the primary at 115V and that the single primary has a resistance of 1 ohm. In parallel each primary 1 amp will flow in each coilm and the dissipation will be 1*1 amp^2= 1W. In series 2 amps will flow in each primary and the power dissipated will be 1*2^2=4W
The trafo that comes with say 2 115v primaries is meant to be operated with the windings in parallel at 115 V or at 230 in series. Under normal circumstances the manifacturer sizes the Xsection of the primary wire based on that assumption.
Iron core and losses don't factor into this at all because the size of the core is determined independently for the nominal VA rating.
The primary is going to have twice the resistance it should have and is going to be operated.
Say you have 2 amps going around in the primary at 115V and that the single primary has a resistance of 1 ohm. In parallel each primary 1 amp will flow in each coilm and the dissipation will be 1*1 amp^2= 1W. In series 2 amps will flow in each primary and the power dissipated will be 1*2^2=4W
I would assume that when primaries are in series only 1A flows through ea primary and your calculations may prove that it is the same power in both cases.
I just called Plitron technical department and the guy initially said the power stays the same. After I asked a few more questiones, he eventually stated he is not sure and said he would call me back.😉
I just called Plitron technical department and the guy initially said the power stays the same. After I asked a few more questiones, he eventually stated he is not sure and said he would call me back.😉
I am pretty sure he will call you back to confirm the same power.
JH
PS. O... By the way, where is the sound of your AX? Am I pressing you too much?
JH
PS. O... By the way, where is the sound of your AX? Am I pressing you too much?
This has made for an interesting discussion. I'm going to purchase the correct transformers and save the "big boys" for a possible 800 watt AX (ha). Of course, I'll have to use two 50V 1000V/A transformers per channel...........
Back on earth: 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
Back on earth: 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
I still can't see how it could make sense that the power could stay the same when you are running it at half voltage. The transformer was designed so that for 115 V you need both windings in parallell for full power and likewise for 230 V but in series.
This following is a quote from the site below:
4) Can transformers be operated at voltages other than nameplate voltages?
In some cases, transformers can be operated at voltages below the nameplate rated voltage. In NO case should a transformer be operated at a voltage in excess of its nameplate rating unless taps are provided for this purpose. When operating below the rated voltage the KVA capacity is reduced correspondingly. For example, if a 480 volt primary transformer with a 240 volt secondary is operated at 240 volts, the secondary voltage is reduced to 120 volts. If the transformer was originally rated 10 KVA, the reduced rating would be 5 KVA, or in direct proportion to the applied voltage.
Site:
http://www.acmepowerdist.com/ael10.html
Seems to be half when operated at half the voltage.
/UrSv
This following is a quote from the site below:
4) Can transformers be operated at voltages other than nameplate voltages?
In some cases, transformers can be operated at voltages below the nameplate rated voltage. In NO case should a transformer be operated at a voltage in excess of its nameplate rating unless taps are provided for this purpose. When operating below the rated voltage the KVA capacity is reduced correspondingly. For example, if a 480 volt primary transformer with a 240 volt secondary is operated at 240 volts, the secondary voltage is reduced to 120 volts. If the transformer was originally rated 10 KVA, the reduced rating would be 5 KVA, or in direct proportion to the applied voltage.
Site:
http://www.acmepowerdist.com/ael10.html
Seems to be half when operated at half the voltage.
/UrSv
Since so many people mentioned having contacted victoia Magnetics, I started another thread in the Electronics and Parts forum about a possible group order.
Seems to be half when operated at half the voltage
I don't think so.....
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.
http://www.atc-frost.com/products/design/va.htm
I don't think so.....
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.
http://www.atc-frost.com/products/design/va.htm