Motors 3 Flashcards
The torque produced by a motor overload that pulls the rotor out of synchronization is referred to as ? torque.
Select one:
a.
pull-in
b.
pull-out
c.
reluctance
d.
synchronous
B
A ? may be used to start the rotor rotation and speed it up to almost synchronous speed.
Select one:
a.
motor-generator set
b.
permanent magnet
c.
pony motor
d.
static exciter
C
If a synchronous motor rotor slips out of synchronous speed for a period of time, ? are needed to shut it down.
Select one:
a.
commutators
b.
compressors
c.
discharge resistors
d.
protective relays
D
The current in the stator power circuit is at minimum level when a synchronous motor is at ? power factor.
Select one:
a.
lagging
b.
leading
c.
low
d.
unity
D
In an application of ? circuit logic, a motor must be allowed to decelerate by coasting or braking before being changed to a low speed.
Select one:
a.
accelerating
b.
compelling
c.
decelerating
d.
modified
C
A circuit with ? circuit logic allows the operator to select the desired speed by pressing either the low or high pushbutton.
Select one:
a.
accelerating
b.
circulating
c.
compelling
d.
dynamic
A
? circuit logic is used in applications where a motor or load cannot withstand the stress of changing quickly from high speed to low speed.
Select one:
a.
Accelerating
b.
Circulating
c.
Compelling
d.
Decelerating
D
The relative position of the ? in Schrage AC motors is altered to change the speed of the motor.
Select one:
a.
brushes
b.
rotor windings
c.
slip rings
d.
wye connections
A
A consequent-pole motor with two poles when wired in series has ? poles when wired in parallel.
Select one:
a.
1
b.
2
c.
4
d.
8
C
Damage may occur to an AC motor if the supply voltage is varied more than ? above or below the rated nameplate voltage.
Select one:
a.
3%
b.
5%
c.
10%
d.
15%
C
Torque decreases when the voltage is lower than the rated voltage. With 95% of rated voltage, the torque is ? of rated torque.
Select one:
a.
5%
b.
10%
c.
90%
d.
100%
C
The frequency of the voltage used to control motor speed is called the ? frequency.
Select one:
a.
alternative
b.
carrier
c.
fundamental
d.
static
C
The speed of standard AC squirrel-cage motors is normally varied by changing the number of poles or the ? .
Select one:
a.
applied frequency
b.
current
c.
drive rating
d.
series connection
A
? control is a method of controlling the voltage applied to the armature of a DC motor.
Select one:
a.
AC field-voltage
b.
DC field-current
c.
SCR armature-voltage
d.
Sensorless field-current
C
A ? bearing is a rolling-contact bearing that has cylindrical or tapered steel rollers confined between inner and outer rings.
Select one:
a.
ball
b.
Conrad
c.
friction
d.
roller
D
? roller bearings have a high radial load capacity but are not designed for axial loads and cannot tolerate misalignment.
Select one:
a.
Cylindrical
b.
Ball
c.
Spherical
d.
Tapered
A
? bearings are used in areas of heavy loads where space is limited.
Select one:
a.
Ball
b.
Friction
c.
Needle
d.
Tapered
b
A(n) ? clutch uses a magnetic field to couple a motor to a load.
Select one:
a.
coupling
b.
eddy-current
c.
friction
d.
magnetic
B
A ? is a coupling that connects or disconnects the motor shaft to a drive shaft while the motor is running.
Select one:
a.
clutch
b.
flexible coupling
c.
gear
d.
rigid coupling
A
? transmit torque to and from a pulley through the wedging action of the tapered sides of the belt in the pulley groove.
Select one:
a.
Chains
b.
Timing belts
c.
Timing chains
d.
V-belts
D
? misalignment is the situation where two shafts are parallel but are not on the same axis.
Select one:
a.
Angular
b.
Nonparallel
c.
Offset
d.
Springing
C
The ? alignment method uses two dial indicators to take readings of opposing sides of coupling rims, giving two sets of shaft runout readings.
Select one:
a.
coupling
b.
laser rim-and-face
c.
reverse dial
d.
rim-and-face
C
A(n) ? occurs when current leaves its normal path and travels to the frame of the motor.
Select one:
a.
dead circuit
b.
ground fault circuit
c.
open circuit
d.
overload circuit
B
? is the most common causes of motor failure.
Select one:
a.
Misalignment
b.
Overloading
c.
Rotor failure
d.
Single phasing
B
? is a power supply problem that occurs when one of the 3-phase lines leading to a 3-phase motor no longer delivers voltage to the motor.
Select one:
a.
Phase unbalance
b.
Single phasing
c.
Voltage blocking
d.
Voltage surging
B
A ? motor is an AC motor that uses induction to create linear movement.
Select one:
a.
compensated universal
b.
linear induction
c.
noncompensated universal
d.
stepper
B
The main parts of a universal motor are the field windings and the ? .
Select one:
a.
armature
b.
pigtails
c.
reverse coils
d.
rotor
A
? rely on electric commutation (pulses) to provide motion control.
Select one:
a.
Linear motors
b.
Servomotors
c.
Stepper motors
d.
Synchronous motors
C
A motor is ? when it draws more than rated current.
Select one:
a.
overcycled
b.
overloaded
c.
overshaded
d.
unbalanced
B
A(n) ? is a rigid steel support for firmly coupling and aligning two or more rotating devices.
Select one:
a.
anchor
b.
base plate
c.
dowel
d.
foundation
B
? braking requires more maintenance than any other method of braking.
Select one:
a.
Electric
b.
Friction
c.
Magnetic
d.
Regenerative
B
Plugging a motor to a stop results in high current and heat.
Select one:
True
False
True
? braking can be used to provide an immediate stop, particularly in an emergency situation.
Select one:
a.
Electric
b.
Dynamic
c.
Interlock
d.
Magnetic
A
Power resistors are used with ? braking to dissipate the heat of braking.
Select one:
a.
dynamic
b.
electric
c.
friction
d.
plugging
A
The motor connections are reversed with ? so that the motor develops a reversed torque to brake the motor.
Select one:
a.
friction braking
b.
plugging
c.
reversing braking
d.
rigging
B
