# AC(3 phase)/DC power conversions

#### ak52

Joined Oct 15, 2014
228
Hello all,
I have a few basic doubts regarding AC to DC power conversion calculations.
Please correct me if i am wrong at any stage.

Firstly, when we consider single phase AC system,as a rule of thumb we can equate both the powers like this
DC power = efficiency * AC power or more precisely
Vdc * Idc = efficiency * Vrms * Irms, -------(1)
where efficiency is between 75-90%
All good so far

Now coming to a 3 phase system
DC power = 1.732 * power factor * AC power or it can be re-written as
Vdc * Idc = 1.732 * power factor* V * Irms-----(2)

What is V in the above equation,is it the Line to Line voltage or Line to Neutral voltage?I think it is the Line to Line voltage but i would like to confirm it with you guys first.Also how would equation 2 look like if i would want to write it in terms of efficiency?

#### ErnieM

Joined Apr 24, 2011
8,362
How is the PS connected to the line?

If you have a 4 wire / 3 hot + neutral and you connect your unit directly to these4 lines then you are using the line to neutral voltage.

If you have a 3 wire connection just across the 3 lines then it is the line to Lin voltage. Usually this connection is done thru a transformer. The first way can be direct to the line.

So to sum this up, go a schematic?