Chapter 2 Homework

NEMA requires that motors be able to carry their rated horsepower at nameplate voltage plus or minus

10%

In general operation motors are classified according to the type of power being used as being ___or ___

AC, DC

The duty cycle of a motor is listed on the nameplate as __________ or __________.

CONT, INTER

The phase rating of a motor is listed on the nameplate as ___,____, or ____

DC, 1-phase, 3-phase

The motor nameplate Code letter specifies the locked rotor current rating of the motor in:

KVA per HP

The abbreviation most used for a pushbutton switch is ________.

PB

The three distinct windings of a three-phase motor are referred to as:

Phase A, Phase B, Phase C

The IEC nomenclature for the output leads of a 3-phase motor are identified as __________.

U - V - W

With "low voltage protection" on motor controls

a power failure disconnects service and when power is restored manual restarting is required

The motor nameplate __________ temperature rating is the maximum rated temperature of the air surrounding the motor.

ambient

The plugging of a motor refers to

braking by reverse rotation.

The device used to automatically disconnect the starting winding of a single-phase split-phase motor is called a __________ switch.

centrifugal

The two basic parts of a typical motor circuit are the

control circuit and power circuit.

When a dual-voltage motor is operated at the HIGHER voltage rating the operating

current is lower

For six-lead dual voltage 3-phase motors the 3-phase configuration used for the low voltage is ___ and for high voltage is ____

delta, wye

On electrical diagrams, conductors that cross each other and make contact are represented by a heavy __________ at the junction.

dot

A pressure switch would be classified as a load.

false

When more than one electrical load is connected in a rung of a ladder diagram, the loads are normally connected in series.

false

When replacing a motor, selecting the same __________ ensures that the mounting mechanism and hole positions will match.

frame size

The speed of an AC induction motor depends on the __________.

frequency of the electrical power supply and the number of poles built into the motor

Inverter-duty describes a class of motors that are capable of operation

from a variable frequency drive

Which of the following types of motor starters connects the motor directly to the supply line on starting?

full voltage starter

In a ladder diagram, the electrical components are arranged according to their ____ in the circuit.

function

Additional START or ON control devices are wired

in parallel

The __________ is the electrical device in a ladder diagram that uses the power supplied from L1 to L2.

load

Two-wire control circuits use a __________-contact type of control device.

maintained

Three-wire control circuits use a __________-contact type of control device.

momentary

A motor nameplate indicates that the motor has a "service factor" of 1.25. This means that the

motor can on occasion safely develop 125% of its rated HP

Information required to identify a motor is contained on the motor __________.

nameplate

The two general classifications of motor enclosures are __________ and __________.

open, totally enclosed

For a __________ connection of loads, the voltage across load is the same as that of the applied voltage.

parallel

On a ladder diagram, a rung is defined as a complete _____ from L1 to L2 that contains a load.

path

A wiring diagram is intended to show the actual ____ of all components

physical location

With a "selector switch" a

plunger actuates the contacts

The circuits on most motor control schematics can be broken down into being part of the __________ circuit or the __________ circuit.

power, control

The rotating part of an AC motor is referred to as the __ and the stationary part is called the ___

rotor, stator

A ladder diagram is a(n) ____ representation of an electric circuit.

schematic

In a dual-voltage split-phase motor, the two run windings are connected in __________ for the HIGH voltage operation.

series

Which of the following diagrams shows an electrical installation reduced to its simplest form?

single-line diagram

Industrial applications use DC motors because the ____/ ____ relationship can be easily varied

speed, torque

A "motor starter" is an electric controller used to __________ a connected motor

start, stop, and protect

The amount the motor winding temperature will increase above the ambient at full load is specified according to the nameplate __________ rating.

temperature rise

The motor term "auxiliary contact" refers to

the contact of a switching device in addition to the main circuit contact.

Ladder diagrams show

the electrical connections

On a block diagram the arrows connecting the blocks indicate

the general direction of current paths

The nameplate of a motor indicates that it is thermal protected. This means __________.

the motor has a built-in thermal device

A fuse is never placed on the grounded side of the circuit.

true

A squirrel cage rotor has no physical electrical connection to it.

true

Three-phase motors are self-starting on their running windings.

true

When conductors cross but make no electrical contact, this is represented intersecting lines with no dot.

true

For a six-lead dual voltage with a low voltage rating of 220 volts, the high voltage rating would be

380 volts

Single-phase motors are

all of these

The line frequency of a motor is abbreviated on the nameplate as:

all of these

Standard NEMA motor insulation classes are given by:

alphabetic classification (A, B, F, H, etc.)

A conduit layout diagram normally does not include the number and size of wires to be run in the conduit.

false

A motor with a low power factor rating will draw less current for the same horsepower than a motor with a high power factor.

false

If a control circuit is supplied from a grounded circuit, it makes no difference what side of the line is grounded.

false

In a ladder diagram, components are arranged according to their physical position in the installation.

false

The HP nameplate rating of a motor is a measure of the full load output power the shaft of the motor can produce without stalling.

false

The conductors feeding current to a large motor would be part of the control circuit.

false

The heavier lines on electrical diagrams usually indicate the control circuit conductors.

false

The nameplate efficiency value of a motor is its efficiency rating with no load applied to the motor.

false

The rated nameplate speed of a motor is its approximate speed with no load applied.

false

The single-line diagram uses blocks along with a single-line to show all the major components of a system.

false

The use of DC motors is more widespread than the use of AC motors.

false

Two-wire control circuits are designed to protect against automatic restarting when power returns after a power failure.

false

When a split-phase motor is operated with a capacitor in series with one of the stator windings the

starting torque is higher

On a ladder diagram, all wires that connect to a common point are assigned __________.

the same numbers

All 3-phase motors are wired so that the phases are connected in either Wye or Delta configuration.

true

All electrical components are normally drawn in the off-state or de-energized position.

true

At least one load must be included in each rung of a ladder diagram.

true

Broken lines on a diagram are usually used to show mechanical connections.

true

Dynamic braking can be used with DC motors to bring the motor to a stop without the aid of a mechanical brake.

true

Magnetic motor starters allow a motor to be controlled from a remote location.

true

Motor terminal markings are usually used to tag only those terminals to which connections must be made from external circuits.

true

Nine-lead dual 3-phase motors have a 2-to-1 voltage difference.

true

No wires or components are normally shown on block diagrams.

true

Single-phase AC motors are typically constructed in small horsepower sizes.

true

Symbols for electrical devices may not always resemble the real thing.

true

The direction of rotation of a DC motor depends on the direction of the magnetic field and the direction of the current flow through the armature.

true

The motor nameplate Design letter is an indication of the motor's torque speed curve.

true

Wires common to each other are usually identified by the same number.

true

Wiring diagrams are used when installing and tracing wires in electrical installations.

true

With low-voltage protection, when power is restored after a power failure, manual restarting is required.

true

You can reverse the direction of rotation of a 3-phase motor by reversing any two of the three main power leads to the motor.

true

To differentiate between NO and NC contacts on a ladder diagram, NC contacts are identified as a number which is

underlined