# 3 Phase Rectifier

Discussion in 'General Electronics Chat' started by enigmapaul, Dec 12, 2008.

1. ### enigmapaul Thread Starter New Member

Dec 12, 2008
2
0
Hi,

If I need a solid 350VDC output from a 3-phase generator, can someone point me to the equations to use to figure out how much peak to peak voltage I must maintain on the output of the generator to achieve the DC voltage out using a 3-phase rectifier?

Thanks!

Apr 5, 2008
15,806
2,390
Hello,

When you rectify an 3 phase signal, the top voltage is the same as in a single phase.
The avarage voltage will be higher as in a single phase, beacouse the ripple is much smaller.

Greetings,
Bertus

3. ### enigmapaul Thread Starter New Member

Dec 12, 2008
2
0
Thanks what is the equation to determine the average DC voltage output of the 3 phase rectifier?

Apr 5, 2008
15,806
2,390
5. ### mik3 Senior Member

Feb 4, 2008
4,846
63
Vdc=1.35*VL

Vdc=output voltage of the rectifier
VL=RMS value of the line voltage

6. ### SgtWookie Expert

Jul 17, 2007
22,183
1,729
That's an extremely rough approximation even at low voltages, and the accuracy is much worse at higher voltages.

A closer approximation would be:
Vdc=1.4142*(VL-VF)
where:
Vdc= output of the rectifier
VL = RMS of the line voltage
VF = Forward voltage of the rectifier(s) in series
But this still does not account for smoothing capacitors and current in the circuit.