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Old 21st January 2013, 10:30 AM   #2411
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Quote:
Originally Posted by tranceanddance View Post
for PSU spec 55vac 25A they count(where I order transformer) for me 2500Wt transformer! how it can be?!!! ((
maybe 25A/secondary, so 50A in parallel?
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Old 21st January 2013, 11:09 AM   #2412
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i dont understand why they count parallel 50A?

what I should exactly say to transformer factory?

I said to them P=1000wt, +-55vac, 25A

maybe anything else I have to specify more to them?

Last edited by tranceanddance; 21st January 2013 at 11:15 AM.
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Old 21st January 2013, 12:08 PM   #2413
AndrewT is offline AndrewT  Scotland
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you need to tell the supplier/manufacturer:
Input voltage
Output voltage
Number of secondary windings
Regulation
VA

eg.
230:40+40Vac dual secondary. 1000VA, 3 to 4% regulation.

That's all.
You don't need to know the current rating, you don't need to tell them the current rating.
You ask why?
Because you are not using the transformer to feed AC to a resistor load.
And that 1000VA will satisfactorily power a 500W to 1000W amplifier or set of amplifiers with a total maximum output of 500W to 1000W.

You are feeding the output to a capacitor input filter. The current rating goes out the window when a non resistor load is used.
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Old 21st January 2013, 01:27 PM   #2414
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Thank you very much !
ps: what do you mean 3 .. 4% 'regulation' ?
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Old 22nd January 2013, 10:55 AM   #2415
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Quote:
Originally Posted by AndrewT View Post
you need to tell the supplier/manufacturer:
Input voltage
Output voltage
Number of secondary windings
Regulation
VA

eg.
230:40+40Vac dual secondary. 1000VA, 3 to 4% regulation.

That's all.
You don't need to know the current rating, you don't need to tell them the current rating.
You ask why?
Because you are not using the transformer to feed AC to a resistor load.
And that 1000VA will satisfactorily power a 500W to 1000W amplifier or set of amplifiers with a total maximum output of 500W to 1000W.

You are feeding the output to a capacitor input filter. The current rating goes out the window when a non resistor load is used.

I understood it, but anyway.. I sended my psu info allready to 3 manufacturers and all of them ask me what current have to be at secondary...if I tell them 25A, they said it will be 2*55V*25A=2750VA transformer!!!
please, help why like this....

Last edited by tranceanddance; 22nd January 2013 at 10:58 AM.
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Old 22nd January 2013, 02:30 PM   #2416
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and if I dont tell to them any current, they write this spec for ready psu:

1350 VA, 50Hz 220В

1: +55В under load 12,3А
2: -55В under load 12,3А

(D*d*H) - 186*47*78 мм
9,92 kg


or


1000 VA, 220v, 50Hz
1: +55В under load 9,1А
2: -55В under load 9,1А
(D*d*H) - 184*52*74 мм
9,11 kg


but 9,1A or 12.3A dont enough for 2 chanels stereo , am I right?!
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Old 22nd January 2013, 03:06 PM   #2417
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by tranceanddance View Post
.................but 9,1A or 12.3A dont enough for 2 chanels stereo , am I right?!
No, you are not right.
Remember I told you
Quote:
You are feeding the output to a capacitor input filter. The current rating goes out the window when a non resistor load is used.
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Old 22nd January 2013, 04:34 PM   #2418
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ok! then why they write on psu spec " xxV under _xxA load_ " ? I mean..for what ?
thank you
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Old 22nd January 2013, 08:18 PM   #2419
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I'm sorry about stupid quiestion, they write it for R load of course...

so, Iam ordering this one

1000 VA, 220v, 50Hz
1: +55В under load 9,1А
2: -55В under load 9,1А
(D*d*H) - 184*52*74 мм
9,11 kg

hope everything is clear now to start the amp building
and big thanks to all DIY users for help
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Old 27th January 2013, 08:54 AM   #2420
44250 is offline 44250  Serbia
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they request current ratings for all secondary windings because not all secondary windings must have the same power ratings. in case of 1000VA transformer,they donīt know if you need 700VA from one 55Vac secondary,100VA from other 55Vac secondary,190VA from one 18Vac secondary and 10VA from one remaining 18Vac secondary/or you need 950VA from both 55Vac secondaries to power amp and 50VA to power other circuites in amp other than output stages. not all the secondary windings must have the same power ratings,but they all together should have power equall to a primary winding/total transformer power.

If you are building 2 B500 chanels,i would use at least 1500VA transformer.

Last edited by 44250; 27th January 2013 at 08:57 AM.
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