I need some help on Power Supplies.

[Tasos_Eco]

Can anyone help me built a 70VDC/30Amps power supply? What do i need to buy and from which site? Or Can i find ready supplies with 70VDC/30A output and 230VAC input?

[Al_The_Man]

There are lots of power supply posts here in the Electronics and stepper sections that should give you a good start.
Al

[Tasos_Eco]

Al, i have read many of the posts, but i thought it could be better to start one new discussion.
I think i need a 1500VA transformer, a 34286uf capicator and a rectifier bridge over 70V and 30A, please correct me if i am wrong.
I just want to know if i can connect two smaller transformers and what their vaules would be?

[Al_The_Man]

The AC secondary needs to be between 50 & 52vac allowing for the bridge drop, a 50,000µfd capacitor will give you 2.5% ripple, which at 70vdc will be 4.9v ripple on 60hz supply. Based on the calculated value of ac current (Iac= 1.8*Idc) your VA would be over 3.7Kva, but If your duty cycle is going to be low, I would tend to cut back on that figure. If the transformers are closely matched you can put them in parallel, take care to phase them correctly before connecting.
The above calculations are based on 70v at a current of 30amps.
Al

[Tasos_Eco]

Thank you Al. I understand lot of things, but not all, my english are not very good, so do you know if there is any site that i can order a custom "cheap" power supply at 70VDC/30A?

[Al_The_Man]

Custom and cheap do not usually go together You would probabally be better off obtaing the separate items and building you own. You would have to find an electronic supply house that stock these kind of items.
Al