wire gauge

The short answer to your question is 6 ga copper (50a per phase) but I am not sure the question is right.

Hello i need to calculate the wire gauge for 3 phase 4 wire system ( 3 phase

• 1 neutral). total load is 150 Amp and load is not balanced .Different devices are connected in single phase confgiuration ( phase to neutral using each phase wires), no device is connected in phase to phase configuration. what wire gauge will be used for power lines for a balanced power system. also what wire gauge will used for neutral wire. will it carry total 150 Amp current or only 50 Amp current. waiting for postive response.

If this is still max 50A per phase the phase wires are still 6 ga.

With high harmonic current on the neuutral, some of the harmonic currents add. That could result in more than 50 A on the neutral. Harmonics are produced by rectification to DC as in computer power supplies and variable frequency drives.

bud--

If it is only 50amp per phase, that would be a 50amp 3 phase circuit. If you are using a 60 amp breaker the wire would be: Feeders - 6 gauge Neutal - 6 gauge Ground - 8 gauge

However thare are exceptions depending on what this circuit is for. Is it feeding a motor, a dist. panel, or what? The above is feeding a dist panel. If a motor why a neutal? We just need more info here.

The Voltmaster

The correct answer is "Hire a good electrician or maybe an electrical engineer " - the nature of this question gives me great doubt that an answer gotten off a newsgroup will provide a safe solution.

Bill

And doesn't this apply to so many questions in this NG For example-- How do I parallel 2 1000kva alternators? The real answer is much like the answer to -- How do hedgehogs make love? Answer.. Very carefully.

But the devious ill-informed and irrelevant rubbish sometimes supplied to this type of question leave a lot to be desired.

When the load is perfectly balanced on the three phases there will be no current flowingf on the neutral wire. When the load is not balanced, there will be current floating on the neutral. With pure linear loads the neutral current can be up to the current of one phase (the current of phase carryign the highest current, think situation where power is taken only fron one phase). If the load is non-linear then the the neutral current can in extreme case be the sum of all phase currents (all load third harmonic). Dimmers and switch mode power supplies without power factor correction do generate a large number of odd-order harmonics (worst is third). For example with large dimmer loads the usual practice is to specify the neutral conductors at 130% of phase conductors (rated for 130% of nominal phase current).

Then if you are running the cable for more than fifty feet or so, you need to consider voltage drop, and might have to increase your conductor size.

--Dale