3P 3W Amperage
- Thread starter farmaped
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brian john
Senior Member
- Location
- Kilmarnock, Va
- Occupation
- Retired after 52 years in the trade.
Depends what it feeds, two legs may feed controls or a large control transformer, as well as the 3 phase load. In a heater it may feed different single phase heater elements or two legs may feed the single phase fan.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Not without knowing at least one more variable.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
If it is a 3 phase 3 wire circuit, meaning 3 'hots' with no neutral, then you only need measurements of two legs to define the current flow on the third leg.
Assuming no faults, and ignoring things like leakage through insulation and capacitive coupling to ground, the net current flow on all three wires must be zero, meaning that any current flowing on one wire must be balanced by current flowing in the opposite direction on the other two wires.
The vector sum of <current on leg A> + <current on leg B> + <current on leg C> = 0
The kicker is that you can't simply measure the RMS current on the two legs; you need to know the phase angles as well in order to take the vector sum. But if you know the current and phase angle of legs A and B, then you can solve the above equation to figure leg C.
-Jon
Assuming no faults, and ignoring things like leakage through insulation and capacitive coupling to ground, the net current flow on all three wires must be zero, meaning that any current flowing on one wire must be balanced by current flowing in the opposite direction on the other two wires.
The vector sum of <current on leg A> + <current on leg B> + <current on leg C> = 0
The kicker is that you can't simply measure the RMS current on the two legs; you need to know the phase angles as well in order to take the vector sum. But if you know the current and phase angle of legs A and B, then you can solve the above equation to figure leg C.
-Jon
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