Exam 8: Feeders

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).

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

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

are multiples of a fundamental frequency.

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

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

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

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

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.

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

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

The ampacity is the allowable ampacity multiplied by the factor.

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

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

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

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

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

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 ____.

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