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The six ungrounded hot conductors feeding the luminaires count as current-carrying conductors. Because of Because the neutral must be counted, there are eight current-carrying conductors. The Table If the calculated load in accordance with the provisions in While it may be permitted to install a neutral conductor that is smaller than the ungrounded conductors, it is not required. The installed neutral conductor can be the same size as the ungrounded conductors.

Caution is advised if the feeder or service has a small neutral load. If the conductor size is based on the calculated neutral load only, it could be smaller than the minimum required size. In accordance with Before selecting the feeder-circuit grounded conductor, compare the minimum size required for the calculated load with the minimum size equipment-grounding conductor; then, select the larger of the two.

For example, a ampere panelboard protected by a ampere breaker will be installed in an area within an industrial plant. The size of the ungrounded feeder conductors will be kcmil copper.

The calculated neutral load is 67 amperes. What is the minimum size conductor required for the neutral? Based on the calculated neutral load only, the minimum size conductor from Table Be the first to get exclusive content straight to your email. We promise not to spam you. You can unsubscribe at any time.

Recommended Articles. More Articles. Compare the minimum size required for the neutral calculated load with the minimum size equipment-grounding conductor from table The neutral conductor must not be smaller than the required grounded electrode specified in table Email This BlogThis! No comments:. Newer Post Older Post Home.

Subscribe to: Post Comments Atom. Definitions: Neutral Conductor : is The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.

Four examples of a neutral point in a system see below image An example of the first system is a three-phase, four-wire wye-connected transformer. An example of the third system is an ungrounded delta system which is a type of three-phase delta system that is sometimes used in industrial facilities An example of the fourth system is a direct current system used to supply power derived from batteries, power supplies, generators or other sources to the loads.

Exception for Rule 1: For 3-wire, 2-phase or 5-wire, 2-phase systems, the maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor multiplied by percent. Definition: Nonlinear Load: A load where the wave shape of the steady-state current does not follow the wave shape of the applied voltage.

Very little voltage between neutral and earth may exist as the neutral is solidly connected to earth at the sub-station and it may rise if earthing of sub-station is not working properly. Under faulty conditions, for instance the fuse or the circuit breaker protecting the feeder does not trip in the case of earth fault on one of the lines, the neutral may attain a much higher potential with respect to the earth. Under such conditions, there will be heavy voltage drop across the sub-station earth due to fault current which may give quite severe electric shock.

When the neutral wire in a 3 — phase, 4 — wire system is disconnected, the loads which are connected between any two line conductors and the neutral are get connected in series and the potential difference across the combined load becomes equal to the line voltage.

The potential difference across each load is changed according to the rating of the load. Illustration : The effect of disconnecting neutral wire in a 3 — phase 4 -wire system can be explained more clearly by the following illustration:.

The simplified diagram is shown in Figure b. If the neutral wire is disconnected, the two loads R 1 and R 2 are get connected in series and the potential difference across them becomes equal to the line voltage i. In this process, the voltage across the high resistive load may rise more than the designed value and may damage the high resistive load.

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