AC Fundamentals

Question 1

The amount of power that appears to be
present when voltage and current are measured on a feeder circuit.
The unit is the volt-ampere

Answer 1

Apparent Power

Question 2

The ability of a capacitor to limit current

flow is known as

Answer 2

Capacitive Reactance

Question 3

The voltage induced in an inductor

by its own magnetic field.

Answer 3

Counter Electromotive Force

Question 4

Coil connections where the opposite ends of the three

coils are connected together

Answer 4

DELTA

Question 5

The number of times a generator rotates in one

second.

Answer 5

Frequency

Question 6

the unit of measure for frequency, just as volts

is the unit of measure for electrical pressure.

Answer 6

Hertz (Hz)

Question 7

the ability of a conductor to oppose a

change in current.

Answer 7

Inductance

Question 8

The current limiting property of an inductor.

Answer 8

Inductive Reactance

Question 9

a device that uses the electrical energy of the

source to accomplish some useful purpose.

Answer 9

Load

Question 10

The use of a constantly changing magnetic

field in one conductor to produce a voltage in another conductor.

Answer 10

Mutual Induction

Question 11

The interruption of the complete path needed for

current to flow in a circuit. A broken phase or neutral can cause this

Answer 11

Open Circuit

Question 12

A circuit that has multiple paths for current to

flow.

Answer 12

Parallel Circuit

Question 13

The order in which the three phases are labeled

for rotation purposes.

Answer 13

Phase Sequence

Question 14

refers to how reactance (both capacitive
and inductive) causes voltage and current to be out of phase with
each other.

Answer 14

Phase Shift

Question 15

An electrical instrument used to prove phase

sequence over open points on high voltage lines.

Answer 15

Phasing Meter

Question 16

the relationship between true
power and apparent power and can range from 0% (zero) to 100%.
100% means that all of the power produced in a
system is available for use.

Answer 16

Power Factor

Question 17

an acronym for root means square and is a value of
AC voltage that will produce the same amount of power as a like
value of DC voltage.

Answer 17

RMS

Question 18

portion of a three-phase motor it is

mounted to the shaft of the electric motor.

Answer 18

Rotor

Question 19

A small voltage induced in a conductor when an
AC current is applied to that conductor. The small induced voltage
has a polarity opposite to the applied voltage.

Answer 19

Self Induction

Question 20

A circuit that has one path for current to flow.

Answer 20

Series Circuit

Question 21

A circuit that does not have a load, or in which the

load has been bypassed.

Answer 21

Short Circuit

Question 22

A graphical representation of what is happening to

voltage in an AC circuit over a period of time.

Answer 22

Sine Wave

Question 23

The stationary portion of a three-phase motor. They are energized by each phase of the source, which produces a
rotating magnetic field and causes the rotor to rotate.

Answer 23

Stator

Question 24

The amount of power used in a circuit when phase
shift is accounted for. will always be equal to or less
than apparent power.

Answer 24

True Power

Question 25

A value used to measure reactive power in a pure inductive | circuit.

Answer 25

VARs

Question 26

Coil connections where the single like ends of the three coils are connected together. This connection is also referred to as a star connection

Answer 26

WYE

Question 27

Explain Basic Circuits

Answer 27

Electrical circuits require a source, a complete conductive path, and a load. If the conductive path is broken, an open circuit results. If the load is bypassed, a short circuit occurs. There are two basic types of circuits. A series circuit has only one path for current to flow, while a parallel circuit has more than one path for current to flow.

Question 28

Explain Capacitors

Answer 28

A capacitor is a device that stores electrical energy in an AC circuit. Capacitors are used for power factor correction to counteract inductance, which is caused by inductive loads (transformers and motors). It can be said that capacitance is the opposite of inductance. Without capacitors, the power factor would fall, which would result in dim lights and substantial losses for the utility company.

Question 29

Explain Generation Process

Answer 29

Rotating a magnetic field near coiled conductors generates AC power. This principle is based upon the law of charges. The magnet is charged, and as it passes near the coiled conductor, the electrons in that coiled conductor are repelled. As the magnet rotates, the electrons are repelled from one end of the magnet and then attracted by the opposite end. The electrons are said to be alternating in direction, thus the term alternating current.

Question 30

Explain Induction

Answer 30

When current is applied to a conductor, a magnetic field is produced. If the conductor is connected to a source of AC, the magnetic field is expanding and collapsing as the current alternates. It has been observed that when a second conductor is placed within the expanding and collapsing magnetic field that a voltage will be picked up (or induced) in the second conductor.

Question 31

Explain Parallel Principles

Answer 31

The overall power system can be broken down into several parallel circuits. Transmission lines exiting a generating facility are at the same voltage. Each of these lines is parallel to the others, meaning that each line has its own path to and from the substation. If one transmission line goes down, the other lines should be unaffected.

Question 32

Explain Power Factor

Answer 32

Power factor is a way of indicating that portion of the total current and voltage that is producing power. If the voltage and current sine wave are in unison, the power factor is 100%, which is preferred. Inductors will cause the current sine wave to lag the voltage sine wave, which reduces the power factor. Capacitors will cause the current sine wave to lead the voltage sine wave; therefore, if an amount of capacitance is added to a line that is equal to the amount of inductance, the current sine wave will be in unison with the voltage sine wave. A 50% power factor means that only 50% of the power produced is available for use, while a 100% power factor means that all of the power that is being produced is available for use by consumers. Utilities always strive for a 100% power factor.