Philippine Paint Manufacturers Inc. supplied those....
the temperatures here goes as high as 35 degrees....
but if you contemplate buying an oven, then you can get those
non air varrying varnish...
i have yet to find a vacuum pump that i can afford to date,
but i will get them in future....
mine is a hobby, not a manufacturing one...
.
I wanna see the dead blow hammer you use.
I think that's why I started SMPS transformers> cant lose count with 1 turn secondaries
what are you waiting for? single stage pump, recycled cookware, and a few hoses / fittings.
see yer auto air con dealers
this is what i use....
An externally hosted image should be here but it was not working when we last tested it.
testing my isolation traffo...
open circuit shows 31watts core loss and idle current of 180mA...
short circuit testing shows copper loss at 8A primary current cause a voltage drop of 18 volts...
a current traffo was put in series with traffo primary winding and at 8A
primary current cause a 3 volt dc drop across a 1k resistor....
this CT will be used as overload protection, disconnecting
the traffo primary if 8 amp or more is detected...
open circuit shows 31watts core loss and idle current of 180mA...
short circuit testing shows copper loss at 8A primary current cause a voltage drop of 18 volts...
a current traffo was put in series with traffo primary winding and at 8A
primary current cause a 3 volt dc drop across a 1k resistor....
this CT will be used as overload protection, disconnecting
the traffo primary if 8 amp or more is detected...
Attachments
Sir Tony, I can't seem to open the Philippine Electronics Forum so I decided this might be the place to ask you this. (or maybe other members if you see this)
I have a toroidal traffo with 230V primary and secondaries of 42-0-42, 17-0-17 and 0-12. Only other number shown in label is that it is rated 300W. There's nothing in there about the ratings of each secondaries.
Now, I unwound the 42-0-42 to 22-0-22 to be able to power a mono LM3886 amp. Problem is, I don't know the original VA rating of that 42-0-42 so even if I know how to compute change in VA after unwinding, I can't do it unless I know the original.
Can someone at least have a bit of wise guess or estimate about the original VA rating of that 42-0-42 secondary? It won't be 300W right since there are other secondaries. Anyway, amp is from a powered mixer. +-42 powers the power amp, 17-0-17 is for the mixer and other pre I think. I don't know about the 0-12. I just need to know orig. rating of 42-0-42, even if just guesses. At least, guess will be from someone with experience and knowledge regarding these things. Coz, I don't have it.
I have a toroidal traffo with 230V primary and secondaries of 42-0-42, 17-0-17 and 0-12. Only other number shown in label is that it is rated 300W. There's nothing in there about the ratings of each secondaries.
Now, I unwound the 42-0-42 to 22-0-22 to be able to power a mono LM3886 amp. Problem is, I don't know the original VA rating of that 42-0-42 so even if I know how to compute change in VA after unwinding, I can't do it unless I know the original.
Can someone at least have a bit of wise guess or estimate about the original VA rating of that 42-0-42 secondary? It won't be 300W right since there are other secondaries. Anyway, amp is from a powered mixer. +-42 powers the power amp, 17-0-17 is for the mixer and other pre I think. I don't know about the 0-12. I just need to know orig. rating of 42-0-42, even if just guesses. At least, guess will be from someone with experience and knowledge regarding these things. Coz, I don't have it.
0.8mm diameter is more like the primary thickness.
0.8mm diameter is 0.502sqmm.
Assuming a current density of 3A/sqmm you get 1.5Aac and if it were 6A/sqmm then you get 3Aac.
42Vac + 42Vac @ 1.5Aac comes to 126VA (3A/sqmm), whereas 6A/sqmm gives 252VA
An old good toroid from 20 or 30years ago would probably be wound with wire @ 3A/sqmm to 3.5A/sqmm
A modern very cheap toroid with a high regulation might use 4.5A/sqmm to 5A/sqmm
A good modern expensive low regulation toroid would probably stick with the current densities typical of 30years ago.
0.8mm diameter is 0.502sqmm.
Assuming a current density of 3A/sqmm you get 1.5Aac and if it were 6A/sqmm then you get 3Aac.
42Vac + 42Vac @ 1.5Aac comes to 126VA (3A/sqmm), whereas 6A/sqmm gives 252VA
An old good toroid from 20 or 30years ago would probably be wound with wire @ 3A/sqmm to 3.5A/sqmm
A modern very cheap toroid with a high regulation might use 4.5A/sqmm to 5A/sqmm
A good modern expensive low regulation toroid would probably stick with the current densities typical of 30years ago.
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Sir Tony, I can't seem to open the Philippine Electronics Forum so I decided this might be the place to ask you this. (or maybe other members if you see this)
I have a toroidal traffo with 230V primary and secondaries of 42-0-42, 17-0-17 and 0-12. Only other number shown in label is that it is rated 300W. There's nothing in there about the ratings of each secondaries.
Now, I unwound the 42-0-42 to 22-0-22 to be able to power a mono LM3886 amp. Problem is, I don't know the original VA rating of that 42-0-42 so even if I know how to compute change in VA after unwinding, I can't do it unless I know the original.
Can someone at least have a bit of wise guess or estimate about the original VA rating of that 42-0-42 secondary? It won't be 300W right since there are other secondaries. Anyway, amp is from a powered mixer. +-42 powers the power amp, 17-0-17 is for the mixer and other pre I think. I don't know about the 0-12. I just need to know orig. rating of 42-0-42, even if just guesses. At least, guess will be from someone with experience and knowledge regarding these things. Coz, I don't have it.
power capacity depends on the physical dimensions of your torroid core....and its weight....
you can compare your torrid with those found here....Toroidal Power Transformers for 117V/60Hz Operation
Based on neurochrome website's spreadsheet, a mono LM3886 amp powered +-30V with a crest factor of 6 dB would need a 74.3VA transformer. Since I'll be using it for guitar, I guess it's only ideal to design it with that crest factor in mind.
Since I unwound the traffo by about half the original voltage, I can expect half the original VA right? So with 126 VA, new rating would be 63VA which is not enough for my purpose. However, if it is rated 252VA, it would give the 22-0-22 a rating of 126VA which is more than enough for a mono LM3886.
I just hope I got a higher VA in there. Or else? What's the worst thing that can happen?
Since I unwound the traffo by about half the original voltage, I can expect half the original VA right? So with 126 VA, new rating would be 63VA which is not enough for my purpose. However, if it is rated 252VA, it would give the 22-0-22 a rating of 126VA which is more than enough for a mono LM3886.
I just hope I got a higher VA in there. Or else? What's the worst thing that can happen?
that is gage#20, at 500cm per ampere is good for about 2.44A, so that if you multiply that by 84, then you have 205 volt amperes...
bear in mind that core capacity does not automatically equate to copper capacity...
Based on neurochrome website's spreadsheet, a mono LM3886 amp powered +-30V with a crest factor of 6 dB would need a 74.3VA transformer. Since I'll be using it for guitar, I guess it's only ideal to design it with that crest factor in mind.
Since I unwound the traffo by about half the original voltage, I can expect half the original VA right? So with 126 VA, new rating would be 63VA which is not enough for my purpose. However, if it is rated 252VA, it would give the 22-0-22 a rating of 126VA which is more than enough for a mono LM3886.
I just hope I got a higher VA in there. Or else? What's the worst thing that can happen?
it seem you have more than enough for your needs...
o, Sir Tony. Sorry for posting here ha
Di talaga ako mkapasok sa elab eh (I can't enter elab forum)
May idea ka po kung bakit? (do you have any idea why?)
this is an english speaking forum.....
Load both windings to deliver 2.4Aac + 2.4Aac into 9r17 + 9r17 and check how hot it gets after 30minutes.Based on neurochrome website's spreadsheet, a mono LM3886 amp powered +-30V with a crest factor of 6 dB would need a 74.3VA transformer. Since I'll be using it for guitar, I guess it's only ideal to design it with that crest factor in mind.
Since I unwound the traffo by about half the original voltage, I can expect half the original VA right? So with 126 VA, new rating would be 63VA which is not enough for my purpose. However, if it is rated 252VA, it would give the 22-0-22 a rating of 126VA which is more than enough for a mono LM3886.
I just hope I got a higher VA in there. Or else? What's the worst thing that can happen?
22Vac+22Vac @ 2.4Aac+2.4Aac is equivalent to an output rating of 105.6VA