310

A 10°C increase in the operating temperature can decrease the life expectancy of a DC motor by as much as ___.

1/2

Single-phase AC motors are readily available in hp ratings of 1/6 to ___.

10

The rotating magnetic fields in a 3Ø motor are ___ electrical degrees apart.

120

Three separate winding sets are contained in the stator of a 3-phase motor. These are set at ___ degrees apart.

120

A 3-phase, 15 HP, 230/460-volt motor has a nameplate FLA = 38/19. If operated at 230 volts, ___ amps of current would flow in each motor winding.

19

Dual-voltage 3-phase motors have ___ windings per phase.

2

A 25 hp motor has a nameplate SF = 1.10 and FLA = 60. Without damage, this motor can be overloaded so that it pulls ___ amps, for a short period of time, at rated voltage.

66

What is the efficiency of a 10 hp DC motor that draws 31 amps at 300 volts?

80%

A 50 HP, 480-volt, 3Ø motor has FLA = 53 on its nameplate. The power factor is about 89%. The efficiency of this motor is about ___%.

95.1

The motor winding leads in Drawing ___ are correctly numbered.

A

___ is (are) a type (types) of DC motor(s). Series Shunt Compound Permanent magnet

All of these

I

Among the terminal box connection drawings shown in Figure 229.214, Diagram ___ is correctly drawn for a 9-lead, wye-wound, dual-voltage motor connected to low (240V) voltage.

NEMA Design ___ motors are the most commonly used motors.

B

___ are the most common NEMA motor insulation classes.

B and F

A(n) ___ is a device that changes the direction of current flow through the armature loop.

Commutator

A commutator is a device that changes the direction of current flow through the armature loop in a(n) ___ motor(s).

DC

If a motor has field leads that are marked F1 and F2, this is a ___ motor.

DC motor

FLA is an abbreviation for ___.

Full Load Amperage

___ torque is the torque required to produce the nameplate-rated output power (horsepower) and speed (RPMs) when driving a load.

Full-load

DC motors manufactured in the United States are generally rated in ___.

HP

The speed of a single-phase AC motor can be easily controlled by changing the ___.I. frequency II. number of poles III. voltage

I or II only

___ is a basic type of 3-phase motor.I. Squirrel-cage induction II. Wound-rotor III. Synchronous

I, II & III

___ provides standards for the construction of motors and other electrical equipment.

NEMA and IEC

4.6

Refer to Figure 229.303. Each winding is rated to carry ___ amps of current.

A

Refer to the motor nameplate shown in Figure 230.110. If the supply circuit is 120 volts, you would connect as shown at ___ where the motor leads are connected to the T-strips.

half

Refer to the motor nameplate shown in Figure 230.110. When the motor is connected to a 230-volt circuit, the motor branch circuit current is ___ what it would be for a 115-volt circuit.

II only

Refer to the nameplate shown in Figure 230.122. Drawing ___ at the right shows the correct lead numbering and winding connections for the motor.

7 & 9

Refer to the nameplate shown in Figure 230.122. For this motor you would expect to measure between 0.2 and 20 Ω between leads ___.

1 & 9

Refer to the nameplate shown in Figure 230.123. For this motor you would expect to measure between 0.2 and 20 Ω between leads ___.

To reverse the direction of rotation for a single-phase motor, the ___ connections to line 1 and line 2, respectively, are reversed.

T5 & T8

A motor in a(n) ___ enclosure can be used outdoors.

TENV

II only

The motor winding leads in Drawing ___ (shown below) are correctly numbered.

___ is the turning force exerted on the armature in a motor.

Torque

A shunt DC motor is a type of DC motor.

True

A single-phase AC motor consists of a start winding and a run winding.

True

AC motors can be rated in horsepower or kilowatts.

True

II & IV only

Which 1Ø capacitor motor connection diagram, shown above in Figure 228.201, is correct where clockwise rotation is desired?

A ___ motor can be operated from a single-phase AC circuit. series (universal) capacitor synchronous split-phase

all of these

FRAME, on a motor nameplate, indicates physical characteristics of the motor. These characteristics include ___. shaft diameter mounting base dimensions mounting bolt-hole sizes

all of these

Which of the following are types of 1-ph AC motors? capacitor shaded-pole split-phase synchronous

all of these

If a 3-phase motor is connected to power but is not rotating in the desired direction, the rotation can be changed by swapping any two "hot" circuit conductors ___. in the motor terminal box in the safety switch at the circuit breaker feeding the disconnect

any of these

The industry standard used to reverse a DC motor is to reverse the ___ leads.

armature

Large horsepower single-phase AC motors are generally not used where the conditions permit the use of three-phase motors because 1-ph motors ___.I. are less efficientII. require larger circuit conductors

both I & II

The circuit conductors of a DC motor are connected directly to the ___.

brushes

The brushes in a DC motor are made of ___.

carbon

Nine-lead 3Ø motors are usually internally (factory) connected as either a ___ configuration.

delta or wye

A 3-ph motor with six windings will have ___ leads in the terminal box.

either 9 or 12

NEMA Design C motors are characterized by ___ starting torque.

high

The output power produced by a motor is measured in ___.

horsepower

NEMA Design C motors are characterized by ___ starting current.

low

The part of an AC motor that rotates is the ___.

rotor

The most commonly used 3-phase motor is the ___ motor.

squirrel-cage induction

To ensure that shaft rotation is correct and motor-driven equipment is ready to be energized for the first time, ___.

start-up protocols must be followed

A rotating magnetic field rotates in the ___ of a 3-phase AC motor.

stator

An AC motor operates by changing the direction of current through the ___.

stator

For an AC motor, the motor leads in the terminal box originate at the ___.

stator

The ___ is the part of a 3Ø motor that doesn't rotate.

stator

A ___ motor rotates at a constant speed, regardless of how heavily loaded.

synchronous

When a 230/460-volt dual-voltage 3Ø motor is properly connected to a 480-volt circuit, the current through each winding is ___.

the same as it would be for a 240-volt circuit

Prior to disconnecting a 3-phase service drop or lateral, the phase rotation at the service equipment terminals should be checked with a meter and noted. When the service equipment is reconnected, the connection should be made so that the rotation present at the terminals is ___.

the same as the noted phase rotation

The DESIGN letter noted on a motor nameplate indicates ___.

torque characteristics

A ___ motor can operate on either AC or DC power.

universal

A ___ motor utilizes a bank of variable resistors that are external to the motor.

wound-rotor