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3 phase feeder calculation free download |
3 phase feeder calculation free download.Overcurrent Protection
Online Wire Size Calculators & Tables.3 phase feeder calculation free download
Post a Comment Leave a comment to help all for better understanding. Load Calculations for Feeder and Service Neutral. Neutral Conductor : is The conductor connected to the neutral point of a system that is intended to carry current under normal conditions. Neutral Point : is The common point on a wye-connection in a polyphase system or midpoint on a single-phase, 3-wire system, or midpoint of a single-phase portion of a 3-phase delta system, or a midpoint of a 3-wire, direct-current system.
The neutral conductor is a current-carrying conductor. Many believe that, because the neutral conductor is a grounded conductor, it is safe to work on it while it is energized. This is a very dangerous practice that has led t o many serious electric shocks.
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 second system is a single-phase, three-wire system that supplies power to Most of one-family dwellings. 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.
At the neutral point of the system, the vectorial sum of the nominal voltages from all other phases within the system that utilize the neutral, with respect to the neutral point, is zero potential. In some type of delta system, not all phases utilize the neutral; as in below image where phase B does not utilize the neutral. The neutral load must be calculated in accordance section Rule 1: The feeder or service neutral load Basic Calculation. As per NEC section The maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor.
Exception for Rule 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. When calculating the neutral load, it is not necessary to include loads that do not contribute to the neutral current. Rule 2: Permitted Reduction in Neutral Load - 1. Rule 3: Permitted Reduction in Neutral Load - 2.
Where the feeder or service is supplied from a three-wire DC or single-phase AC system; a four-wire, three-phase, three-wire, two-phase system; or a five-wire, two-phase system, it is permissible to apply a demand factor of 70 percent to that portion of the unbalanced load in excess of amperes [ This demand factor is also in addition to any demand factors that may have already been applied.
Rule 4: Prohibited Reduction in Neutral Load - 1. As per Rule 2 above, it is permissible to apply an additional demand factor of 70 percent to a feeder or service neutral supplying household electric ranges.
But, As per Rula 4, applying the 70 percent demand factor is not permissible if the ranges are supplied by a single-phase panel that is fed from a three-phase, four-wire, wye-connected system. Nonlinear Load: A load where the wave shape of the steady-state current does not follow the wave shape of the applied voltage.
Rule 5: Prohibited Reduction in Neutral Load - 2. As per Rule 3 above, where the feeder or service-neutral load exceeds amperes, it is permissible to apply an additional demand factor of 70 percent to that portion of the unbalanced load in excess of amperes.
If the neutral load calculated as per 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. Rule 6: Relation between Sizes of Neutral Conductor and Equipment-Grounding Conductor Compare the minimum size required for the neutral calculated load with the minimum size equipment-grounding conductor from table Rule 6: Relation between Sizes of Neutral Conductor and Grounded Electrode Conductor The neutral conductor must not be smaller than the required grounded electrode specified in table
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