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The Neutral wire should be the same gauge and size of the phase wires. Only the Earth or Equipment wire can be smaller than the phase(hot) wires.

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On a three phase four wire distribution system the neutral can be reduced in size. The neutral only carries the unbalanced load current and should be sized to that current. The highest current load to neutral of the three legs is used to calculate the neutral sizing. There is no reduced neutral allowed on discharge lighting and non linear loads. A demand factor of 70% shall be permitted to be applied to that portion of the unbalanced load in excess of 200 A.

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Q: Why can the neutral wire diameter be reduced in relationship to the phase wires?
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Why you take radius or size of neutral wire half wrt phase conductor?

On three phase services over 200 amps the electrical code allows the electrical contractor to reduce the size of the neutral wire . This saves the customer money. There are conditions as to how much the neutral can be reduced but it is not as low as half the supply conductors. The reason that the neutral can be reduced is that it only carries the unbalanced current on the three phase four wire system.


If in the three phase connection phase to phase voltage is 400v what will be the phase neutral voltage?

The formula to use is, phase voltage /1.73 = phase to neutral (ground) voltage.CommentThere is no such thing as a 'phase to phase', or 'phase to neutral' voltage. The correct terms are 'line to line' and 'line to neutral'. So the above answer should read: line voltage/1.73= line to neutral voltage = phase voltage.


What is reduced phase rule?

f=c-p+1 is the reduced phase rule


Why the diameter of earth leads always more than phase and neutral?

For easy and quick identification of the leads, so that the user does not make mistake while connecting the leads.AnswerFor residential wiring, the earth wire rarely has a cross-sectional area that is larger than the line (not 'phase') or neutral conductors.


What is the code ruling in the US on 3 phase branch circuits and the neutral?

A three phase system will have 3 phase branch circuits and no neutral.


Why neutral cross section is half the phase in three phase cable while it has to carry current of summation of all phase..?

The current carried by the neutral of a three phase four wire system is the un balanced current. If the three phase system was completely balanced on all three phases there would be no need for a neutral, eg a three phase motor. This neutral current will be less that the phase current so a reduction in the neutral size is allowed.


What happens when phase to phase line is connected?

If there is a voltage differential from phase to phase, and a conductance (inverse of resistance) between them, then current (amperes) flows. This is no different than phase to neutral, i.e. voltage across conductance generates current, (I = EC, or I = E/A) except that neutral current is zero in a true phase to phase connection.Note that phase angle is always relative. In phase to neutral, it is relative to (typically) neutral; while in phase to phase, it is relative to the other phase. By Fourier Analysis, the difference between two phases of the same frequency, but of different phase angles, is still a sine (or cosine) wave. Also, by Kirchoff's Current Law, (implied, and I will (sort of) not repeat it here), current entering from one phase and equally leaving via another phase will not reflect at all in the neutral conductor.The simple answer is that connecting phase to phase is a short circuit, just like connecting phase to neutral.CommentThere is no such thing as 'phase to phase' or 'phase to neutral'. The correct terms are 'line to line' and 'line to neutral'.


How does a phase leg connect to a neutral in an electrical circuit?

A phase leg connects to the neutral through the connected load.


Why neutral is not requied in 3 phase?

As far as I understand, you don't need neutral line for connecting appliances that is 3-phase compilant. You only need the neutral line to connect a single phase appliance, which you connect along with one of the three lines.


What is the voltage for each leg on a 480v 3-phase pannel phase to neutral?

Only one neutral conductor is typically in a 3 phase panel.


What is the power line voltage between phase and earthing?

It is the same as phase to neutral. As the neutral is earthed at the electricity suppliers transformer.


What would be the effect on the neutral bar of a 3 phase D B if the main incoming neutral is lost?

A three phase delta system does not use a neutral in its operation.