In detailed Description i was about to run a speaker system which needs 12VAC 3A input power, i missed the adopter given by the company so i was searching alternative. For that i decided to make one myself so i can get 230v 50hz to 12v transformer from local shop. Now how can i get the exact 12vAC 3A output?
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2Possible duplicate of [Choosing power supply, how to get the voltage and current ratings?](https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings) – Vladimir Cravero Apr 24 '17 at 07:34
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3A VDC or VAC output this is unclear and needs to be defined – Voltage Spike Apr 24 '17 at 17:21
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@VladimirCravero this is about transformers, not powersupplies – Voltage Spike Apr 24 '17 at 17:22
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@laptop2d this is about understanding that if you set the voltage, the load picks the current – Vladimir Cravero Apr 24 '17 at 18:27
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I need 3A 12VAC output – amtra Apr 25 '17 at 08:23
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First thing you should do is verify that you transformer is rated up to 3 A, otherwise bad things will happens. If it doesn't, then look for another transformer that can withstand that current at the secondary.
Note that you don't "get the 3 A output" unless your load requires it and your supply can source it. The 3 A rating is just a figure telling you what's the limit of the supply.
A 75 Ohm load will draw 160 mA at 12 V. If you transformer can deliver 3 A, then you'll be perfectly fine.
Enric Blanco
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How can i ensure my transformer will deliver 3A, is there any criteria should i mention while purchase to my desired output – amtra Apr 25 '17 at 08:25
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I think theorically transformer does the job itself. Your system will take how much ampere it needs. But to be safe you should look for a power supply from an electronic market or DIY project which you will use your transformer.
You can check various projects from here :
http://www.instructables.com/howto/power+supply/
Also as Enric mentions in his answer your transformer should be able to give 3A itself.
bcan
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Oki as of now i need a transformer that can withstand upto 3A output so need to add any additional components as i mentions system will draw 3A – amtra Apr 25 '17 at 08:27