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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.
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.
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
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...
The supply is probably 400 v three-phase with 230 v between each live and neutral. On this assumption the current is 49 amps and the copper cable size is 16 mm2 for a run of up to 30 metres.
70mm 4core copper cable
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.
To answer this question a voltage is needed.
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
As example, at 380V the generator produces 685A per phase. Therefore you will require 2 x 120mm2 cables per phase. (1 x 120mm2 cable will support 365A per phase). In total you will require approximately 1/2km of cable to cover the 50m run between the generator and the ATS panel/Load. i.e. 5 phases in total - 2 x 50m cables per phase.
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.