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Power supply help
« on: January 31, 2013, 06:25:59 AM »
Hi guys, I have just bought a 1500VA transformer, 240v primary to 2x 33v secoondary, giving a rectified output of around 46vdc.
Now I get confused. I have assumed 1500va / 33v to provide 45.45 amps output, so I have bought a 50 amp bridge rectifier. Will this be sufficient or do I need a larger rectifier? 
If I need a larger recrifier, I have only managed to find 3-phase varieties with 5 pins. Can anyopne advise whether these can be used single phase, or recommend a suitable alternative please.

If it is of intereset, I am driving 3x  DSG3 8020 drivers which draw a max current of 20 amps each but unlikely to ever draw more than 40 amps. Is there device which could limit the output from the power supply to 40 amps if this is an option?

Offline Hood

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Re: Power supply help
« Reply #1 on: February 01, 2013, 03:34:29 AM »
If I am understanding correctly your transformer is 1500VA in total so that will be 45Amps AC total. I am not sure how the rectifier will be rated, ie is it the AC input or the DC output.  If you want to be on the safe side why not get 2 rectifiers, one for each secondary and combine the DC sides? That way you will only have 7500VA per secondary.

As for limiting the output from the supply, you cant really do that as that is determined by the device connected to it and what it draws, you can limit the current by having a fuse that will blow if the current is exceeded however. As the drives are a max of 20Amp they should never ask for more unless there is a fault in them.

Hood

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Re: Power supply help
« Reply #2 on: February 01, 2013, 03:55:25 AM »
BTW thats 750VA I meant, not 7500 ;D
Hood
Re: Power supply help
« Reply #3 on: February 01, 2013, 05:22:01 AM »
Thanks Hood, I take it that is perfectly safe then to connect the output of each rectifier to a single capacitor?
Re: Power supply help
« Reply #4 on: February 01, 2013, 05:58:38 AM »
Ok, I am starting to find details now showing two outputs connected together. A bit more googling and I will be there!
http://sound.westhost.com/project77.htm

Offline Hood

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Re: Power supply help
« Reply #5 on: February 01, 2013, 07:03:15 AM »
Shouldnt be a problem with that. :)
Hood