kda3310
Senior Member
- Location
- Dry Prong, Louisiana
Ok, then what is the right ampage. That was the first time I used that calcultion. I do not know.
Shared neutral amperage-3 phase system
- Thread starter bw9470
- Start date
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Ok, then what is the right ampage. That was the first time I used that calcultion. I do not know.
chris kennedy
Senior Member
- Location
- Miami Fla.
- Occupation
- 60 yr old tool twisting electrician
Just saw Roger's post.
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kda3310
Senior Member
- Location
- Dry Prong, Louisiana
Ok, is it 1.38 amps? I missed the square root.
Three balanced phases with any neutral that carries no current would also give you no current.
- Location
- Massachusetts
Yes, and the chances of that in the installation he describes are vitally nonexistent.
Maybe.
If he has 30 bundles of 50 conductors wouldn't that be about 375 3-ph+N circuits?
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Now I am wondering about the size of this panel. Did he really mean there are over 1500 wires in this panel?
- Location
- Massachusetts
You are right, mix ups could happen so lets hear your helpful suggestion to the OPs problem.:roll:
Dennis, there are groups and groups and groups of panelboards running these machines and these are not linear loads by any means.
Roger
Why the rolling eyes? I was just pointing out that, with so many conductors, the the method might not be foolproof.
You could do what you're suggesting and that could eliminate maybe most or all of the wrong neutrals. I'd still want to do a continuity check whether there was one or several remaining candidates. As my father was fond of saying, "Measure it twice. Cut it once."
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Okay, I thought they were all in one panel. I guess I couldn't imagine that many circuits for a casino but you would definitely know.
- Location
- Massachusetts
You all know I like MWBCs but I am very surprised the job specs allow the use of MWBCs for this job considering that it is all non-linear loads.
I guess that proves MWBCs can be used successfully.
- Location
- Massachusetts
Because IMPO instead of being helpful you seemed more interested in being negative.
kwired
Electron manager
- Location
- NE Nebraska
You all know I like MWBCs but I am very surprised the job specs allow the use of MWBCs for this job considering that it is all non-linear loads.
I guess that proves MWBCs can be used successfully.
It likely would make a difference if the conductors are carrying minimal load or near max ampacity.
I have no experience in casino wiring but am guessing that in general owners want more circuits with less load per circuit.
A - less load per circuit will likely result in less overload trip conditions.
B - Less machines per circuit means if a circuit goes down less machines are effected.
These machines are their revenue source and they do not want them out of service - especially if there is nothing wrong with them.
- Location
- Massachusetts
I agree with all of that, in fact it was thinking of all of that before you posted it.
But all of that is just as true at offices with dozens of office cubes where I often see engineers require 'super neutrals' on branch circuits that are never going to heavily loaded.
Negative to point out a potential flaw in the method with who knows what consequences?
If you see that as negative, then OK. But it wasn't intended that way.
With phase currents of
a=4.4A, b=3.6A, c=5.2A
I get
4.4 + j0
+
3.6/120 which is -1.8 + J3.12 in rectangular coordinates
+
5.2/240 which is -2.6 -J4.5 in rectangular coordinates
=
0 - j1.38 which is 1.38 at 270 degrees in polar coordinates, so
the magnitude of the current is 1.38a.
a=4.4A, b=3.6A, c=5.2A
I get
4.4 + j0
+
3.6/120 which is -1.8 + J3.12 in rectangular coordinates
+
5.2/240 which is -2.6 -J4.5 in rectangular coordinates
=
0 - j1.38 which is 1.38 at 270 degrees in polar coordinates, so
the magnitude of the current is 1.38a.
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- Location
- Massachusetts
I do see it that way as you did not provide any solutions.
Besoeker said:
That would be great.
I must be missing the obvious, how will this be done with live, in use circuits?
I am assuming this casino is open and the machines in use.
Besoeker said:
Cute.
As some instructors have taught me ... 'it's a real world out there'
In other words, what sounds good from the confines of an office is not always practical on the job.
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