As normally load distribution is done equally in all three phases, almost balanced current is drawn by load and current flow though neutral is very small when compared to the phase and hence difference in cable size is observed
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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. <<>> 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.
The neutral wire should be the same size as your conducters
due to unbalance load 1. Due to negetive phase sequence components in current generator and transformers suppling the load will be over heated 2. The opposite torque on the shaft will damage, rotors are more likely to damage. 3. High current through neutral of the system, normally neutral cable conductor is of lesser size then phase and hence it may be damaged.
As normally load distribution is done equally in all three phases, almost balanced current is drawn by load and current flow though neutral is very small when compared to the phase and hence difference in cable size is observed
In a 3.5 core cable, the neutral conductor carries less current compared to the phase conductors. By reducing the size of the neutral conductor to half, it helps balance the voltage drop and prevents overheating in the cable. This helps ensure the safety and efficiency of the electrical system.
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.
Sir, what is the cable size for 1.5kw 3phase induction motor 400v?
it means 3conductors(ie RYB) and half neutral ie size of neutral would be half size of other conductors...
70mm 4core copper cable
To answer this question a voltage is needed.
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.
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. <<>> 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.
The neutral wire should be the same size as your conducters
due to unbalance load 1. Due to negetive phase sequence components in current generator and transformers suppling the load will be over heated 2. The opposite torque on the shaft will damage, rotors are more likely to damage. 3. High current through neutral of the system, normally neutral cable conductor is of lesser size then phase and hence it may be damaged.
In a perfectly balanced three phase wye system, there is no neutral current, and the neutral conductor is only used to hold the reference point during transient states. As a result, the neutral conductor is often smaller than the three hot legs. However, nothing is perfect, and there will be neutral current. Since there are three phases feeding back to neutral, instead of one, the frequency component of the neutral current is 180 hertz, instead of 60 hertz. If the load represents a full wave rectifier, as in a large DC power supply, or a welder, the neutral current will be 360 hertz. That is the third harmonic of 60 hertz. That frequency is high enough to make the impedance of the neutral cable a factor, so the cable must be sized accordingly.