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NLC Apprenticeship Year 2 Week 1 > AC Fundamentals > Flashcards

AC Fundamentals Flashcards

1
Q

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

A

Apparent Power

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2
Q

The ability of a capacitor to limit current

flow is known as

A

Capacitive Reactance

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3
Q

The voltage induced in an inductor

by its own magnetic field.

A

Counter Electromotive Force

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4
Q

Coil connections where the opposite ends of the three

coils are connected together

A

DELTA

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5
Q

The number of times a generator rotates in one

second.

A

Frequency

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6
Q

the unit of measure for frequency, just as volts

is the unit of measure for electrical pressure.

A

Hertz (Hz)

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7
Q

the ability of a conductor to oppose a

change in current.

A

Inductance

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8
Q

The current limiting property of an inductor.

A

Inductive Reactance

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9
Q

a device that uses the electrical energy of the

source to accomplish some useful purpose.

A

Load

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10
Q

The use of a constantly changing magnetic

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

A

Mutual Induction

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11
Q

The interruption of the complete path needed for

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

A

Open Circuit

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12
Q

A circuit that has multiple paths for current to

flow.

A

Parallel Circuit

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13
Q

The order in which the three phases are labeled

for rotation purposes.

A

Phase Sequence

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14
Q

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

A

Phase Shift

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15
Q

An electrical instrument used to prove phase

sequence over open points on high voltage lines.

A

Phasing Meter

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16
Q

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.

A

Power Factor

17
Q

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.

A

RMS

18
Q

portion of a three-phase motor it is

mounted to the shaft of the electric motor.

A

Rotor

19
Q

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.

A

Self Induction

20
Q

A circuit that has one path for current to flow.

A

Series Circuit

21
Q

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

load has been bypassed.

A

Short Circuit

22
Q

A graphical representation of what is happening to

voltage in an AC circuit over a period of time.

A

Sine Wave

23
Q

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.

A

Stator

24
Q

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

A

True Power

25
Q

A value used to measure reactive power in a pure inductive

circuit.

A

VARs

26
Q

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

A

WYE

27
Q

Explain Basic Circuits

A

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.

28
Q

Explain Capacitors

A

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.

29
Q

Explain Generation Process

A

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.

30
Q

Explain Induction

A

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.

31
Q

Explain Parallel Principles

A

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.

32
Q

Explain Power Factor

A

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.

NLC Apprenticeship Year 2 Week 1 (4 decks)

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