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Exam 8: Feeders

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Question 1

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What wire and cable options do you have for combating excessive neutral current?

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At least one major manufacturer of Type ...

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Question 2

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On a 3-phase, 4-wire, wye system, reduction is allowed for nonlinear loads.

A) no
B) 10 percent
C) 50 percent
D) 75 percent

E) C) and D)
F) All of the above

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Question 3

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To determine a reasonable minimum size for a neutral conductor, two types of loads must be considered- .

NEC 310.10(H) sets forth the requirements for installing conductors.These requirements are intended to ensure the conductors will share the current equally to prevent overloading individual conductors.

The ampacity is the allowable ampacity multiplied by the factor.

To get accurate current readings where harmonics are involved, ammeters referred to as " " must be used.

What are the requirements for installing parallel conductors?

Currents of the 3rd harmonic and odd multiples of the 3rd harmonic (9th, 15th, 21st, etc.) add together in the common neutral conductor of a 3-phase system, instead of canceling each other.These odd multiples are referred to as ____.

In the United States, Hz is standard or the fundamental frequency.

For installations where the nonlinear load is huge, most consulting engineers will specify -rated transformers.

When sizing feeder conductors, noncoincident loads (loads unlikely to be operated simultaneously such as the air-conditioning and the heating) need be included.

Often the load is such that parallel conductors should be considered.This usually occurs with loads over amperes.

are multiples of a fundamental frequency.

If the selected OCPD has a rating greater than 100-amperes, the conductors to be installed shall be selected from either the 75 degrees Celsius or degrees Celsius column of NEC Table 310.15(B) (16) .

wire is seldom used in branch circuits, but because of weight and cost factors, it is frequently selected for feeders and services.

What are the three conditions of failure that may occur with a 3-phase, 4-wire wye system?

What can you do to determine the root cause of voltage drop problems?

If the ampacity of a feeder does not match a standard OCPD rating, then be used.

What three circuit parameters must be known before feeder component selection can begin?

Feeders are the part of the electrical system that connects the branch-circuit to the electrical service equipment.