Some time ago, I purchased a transformer from a surplus sale... I have no specs or anything. Can anyone take a guess at the VA rating?
Dimensions: EI style with laminate plates
Overall
3.75"x6.75"(x6" tall)
Core
3.75"x2.25"(x4" tall)
Windings:
2.25mmx2.25mm square copper secondary
~3mmx3mm square copper primary
(Note that I am removing windings from what was originally step up to get it down to an appropriate amplifier voltage... Also, I need to create a CT)
This monster is quite heavy, ~15 to 20pounds
Any thoughts on loss of performance due to removing windings?
Dimensions: EI style with laminate plates
Overall
3.75"x6.75"(x6" tall)
Core
3.75"x2.25"(x4" tall)
Windings:
2.25mmx2.25mm square copper secondary
~3mmx3mm square copper primary
(Note that I am removing windings from what was originally step up to get it down to an appropriate amplifier voltage... Also, I need to create a CT)
This monster is quite heavy, ~15 to 20pounds
Any thoughts on loss of performance due to removing windings?
Hi
If I remember correctly, the power of a transformer can be (crudely) evaluated by squaring the iron area (ie. center leg or twice outer legs) expressed in cm². The relation is valid for good quality laminations; a derating factor of 0.9 or 0.8 might be prudent for unknown materials. Also, this applies for 50Hz; I suppose for 60Hz you can multiply by 6/5.
LV
PS power can also be estimated by weight, but I have no conversion factor at hand.
If I remember correctly, the power of a transformer can be (crudely) evaluated by squaring the iron area (ie. center leg or twice outer legs) expressed in cm². The relation is valid for good quality laminations; a derating factor of 0.9 or 0.8 might be prudent for unknown materials. Also, this applies for 50Hz; I suppose for 60Hz you can multiply by 6/5.
LV
PS power can also be estimated by weight, but I have no conversion factor at hand.
If you can find a wire gauge table, you can make an informed judgement what current the designer was running at, hence work out VA.
Thanks for the input. Based on your equation, I find that this transformer is ~2700 VA. Can anyone provide a sanity check here? I am surprised by this huge value. Does it sound reasonable that this transformer could be 2.7kVA. I have further confirmed this value with an equation I found online.
in sq.in, VA=(Area/0.16)^2 = 2780VA
I suppose if these equations are somewhat valid then I should have sufficient power for one or two 150W amps 😉 (Note sarcasm)
in sq.in, VA=(Area/0.16)^2 = 2780VA
I suppose if these equations are somewhat valid then I should have sufficient power for one or two 150W amps 😉 (Note sarcasm)
2700VA seems quite large for only 20lb, but the figure is compatible with the primary gauge size, thus I guess it must be correct.
LV
LV
Hi,
Silvio Klaic transformer calculator shows 2.9kVA for a 95mm by 57mm core. Each limb should be 95mm by 28.5mm. The top I and leg of the E should be about 28.5mm or just a little less.
But there is something wrong with the quoted dimensions and/or weight.
The core alone is about 1.9litres from those sizes and should weigh about 15.1kg (about 34lbs).
Then there is all the copper to add in.
Can you confirm the size of the plates in the stack and how thick the stack is?
Silvio Klaic transformer calculator shows 2.9kVA for a 95mm by 57mm core. Each limb should be 95mm by 28.5mm. The top I and leg of the E should be about 28.5mm or just a little less.
But there is something wrong with the quoted dimensions and/or weight.
The core alone is about 1.9litres from those sizes and should weigh about 15.1kg (about 34lbs).
Then there is all the copper to add in.
Can you confirm the size of the plates in the stack and how thick the stack is?
Hi,
removing some of the windings will reduce the VA rating.
Take off 50% of the secondary and you take off 50% of the VA. It's that simple.
It's similar for the primary except that if you remove 50% of the primary you reduce the input voltage by 50% as well, but at the same current, so it equals 50% of the VA.
Increasing the copper on the primary and/or the secondary gives a very small increase in VA rating but the core becomes the limiting factor.
I think the increased VA comes from the reduced losses due to less Isquared R loss.
removing some of the windings will reduce the VA rating.
Take off 50% of the secondary and you take off 50% of the VA. It's that simple.
It's similar for the primary except that if you remove 50% of the primary you reduce the input voltage by 50% as well, but at the same current, so it equals 50% of the VA.
Increasing the copper on the primary and/or the secondary gives a very small increase in VA rating but the core becomes the limiting factor.
I think the increased VA comes from the reduced losses due to less Isquared R loss.
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