3pahse

Hi,

Can we directly connect THREE phases of the mains to gather?? I mean shorting all 3 together?

Thanks

Sure if you want to blow a fuse or start a fire.

Yes you can!
The breakers will pop!

somebody told me that if we do so for 2 of phases then we lose the fuse, but if do so for 3 phases then they will cancel eachothers?

Some folks think HHO works.

I can see where he's coming from. Intuitively it seems wrong...but after looking at the graph it seems to me that it could be true. Every time one wave peaks, the other two waves each have a magnitude that is half as large, and half the magnitude. So for every peak, the other two waves have a sum that is the same magnitude as the peaking wave, except it's opposite polarity so they would cancel. And every time a wave crosses zero, the other two waves have polarities that are of equal magnitude and opposite polarities so the sum of all three would be zero.

EDIT: I graphed it out in MATLAB and it appears that

0 ≡ Asin(ωt) + Asin(ωt-2/3*pi) + Asin (ωt - 4/3*pi)

so the cancellation seems to hold true for all areas of the curve, not just the peaks and zero crossings. But 0V at a single node does not mean no current flow. After all, a common short is some +V connected to 0V.

That is rediculous dk.

Your equation shows that there will be zero volts at the connection point of the 3 phases. However, there is also up to 440V (or whatever it is) at the source of any of the 3 phases, which will be pumping a heap of current through the cable to force the connection to 0V.

It's like saying that connecting a -12V supply to a +12V supply will be a good idea because 0 = -12 + +12.

Electronman said:

somebody told me that if we do so for 2 of phases then we lose the fuse, but if do so for 3 phases then they will cancel eachothers?

Click to expand...

Don't let "somebody" anywhere near electricity.

Ah, yeah. Good point. 0V at a single node doesn't mean no current flow.

(psst, it's spelled ridiculous).

I think I've found the cause of "Mr. Somebody's" mental fart

(Sesame Street Theme starts playing)
Yes, every phase (R,T,S) goes into the center of the star, But look, there is a load in between!
(Sesame Street Theme stops playing)

dknguyen said:

(psst, it's spelled ridiculous).

Click to expand...

That one was for you. Perhaps I should have written (sic.) after it.