Sharing ZC across phases?

[djulien]

I haven't read a post specifically on this topic, so I'll ask (if I missed it somewhere, please pardon my redundance and just point me to the post).

I undertand that Renard needs a ZC signal in order to control the timing for dimming. Also, lights may need to be spread across house circuits In order to avoid overloading one breaker (typically 10A, 15A or 20A).

If I only have one Renard board, or I wish to use one ZC circuit for multiple Renard boards (in order to avoid redundant components and, hence, reduce cost), then do I need to ensure that all the SSRs are powered from the same phase (otherwise the ZC wouldn't match and the dimming would not be correct)?

Also, if I did actually need to spread SSRs across phases (perhaps due to appliance distribution in the rest of the house), but I still wanted to use one shared ZC signal system-wide, would this work as long as I modified the PIC firmware to offset the start delay for the PICs that are driving the SSRs on the "other" phase?

If I did this incorrectly or not at all, would the only consequence be that the dimness of all the SSRs on the "other" phase be off by a half-cycle?

thanks

don

[P. Short]

Zero-crossings occur at the same moment in time for both phases, at least in locales such as the US where the two phases differ by 180 Degrees. It's different in some other places where the phases differ by 120 deg, but you don't have to worry about that in So. Cal.

So one zero-crossing signal works for all, no need to make any changes.

--

Phil

[djulien]

Zero-crossings occur at the same moment in time for both phases, at least in locales such as the US where the two phases differ by 180 Degrees.

I'm not sure where I got that idea (wasn't from this forum, but some past "knowledge"). :oops: Thanks for clearing that up!

don

[RJ]

Zero-crossings occur at the same moment in time for both phases, at least in locales such as the US where the two phases differ by 180 Degrees.

I'm not sure where I got that idea (wasn't from this forum, but some past "knowledge"). :oops: Thanks for clearing that up!

don

The good news is if your one of those locations you will figure it out fast! LOL



RJ

[wjohn]

In Australia, the phases are 120Deg apart, but most houses are supplied with single phase.

John

[avatar-it]

In Australia, the phases are 120Deg apart, but most houses are supplied with single phase.

John

i allways thought that most houses in australia get supplied with 2 phases.

something to do with balancing the load across all 3 phases

Peter

[daviddth]

Most modern houses seem to get 2 phases here now, but I think thats mainly because of the reliance on airconditioners, large power-hungry ovens & cooktops, plus the usual 50" plasma TV's and stereo systems in every room :)

I am lucky to have 2 plases too - one for the house abd shed, and one for the airconditioner, christmas lights & laundry. Now the laundry has been moved, the original phase has never topped at 30A yet... I might have to move the A/C back over to the other phase to gain more room for the chrissie lights lol

[omzig]

Actually, in the US, what many call phases in residential wiring aren't really phases. The two legs of the service come from a center tapped transformer on one of the three phases provided by the power company. The neutral is the center tap and is grounded, so it provides a zero volt reference. Your electrical service is actually a three-wire single-phase service, aka a split-phase service.

[djulien]

"split-phase" sounds familiar. Sorry I mis-stated the original question. :oops:

don

[wbuehler]

Nice information

Thanks

Bill

[kostyun]

Believe it or not - wikipedia has a great reference!

http://en.wikipedia.org/wiki/Split_phase

[kmiller]

Actually, in the US, what many call phases in residential wiring aren't really phases. The two legs of the service come from a center tapped transformer on one of the three phases provided by the power company. The neutral is the center tap and is grounded, so it provides a zero volt reference. Your electrical service is actually a three-wire single-phase service, aka a split-phase service.

To confuse matters more, we also have some 'high-leg delta's'. In this case, there is a three-phase service conected in delta, with one of the transformers being center-tapped and wired split phase. In this case, we get two legs that are 120V to ground, and one that is about 210V to ground. All three legs would be 240V phase-to-phase. If you run across one of these, make sure you do not tie any 120V single phase loads to the high leg. These are typically found in older areas and are not being installed on any new construction.

[omzig]

We used to call them "wild-leg deltas"

[Jeff Millard]

That 208VAC leg is commonly called the "bastard leg" and is often found to be used in industrial lighting. The power company I work for lights most of the switchyards with it.

Jeff