Quiz #6 Flashcards
In a three-phase, squirrel-cage type, induction motor,
the primary rotating magnetic field is established by the
__________.
application of a three-phase
voltage supply
to the stator windings
In general, polyphase induction motors can be started
on full line voltage by means of __________.
across-the-line
starters
The speed of a three-phase squirrel-cage induction-type
motor operating in a fixed frequency system is varied by
changing the __________.
number of stator poles
If there is a reduction in the normally supplied frequency
to a 120/240 volt, three-phase AC current motor from 60
hertz to 55 hertz, the motor would __________.
run at a slower speed
In a 15 HP induction-type motor with a cage rotor, the
current required at standstill to produce starting torque
is approximately __________.
five times the full load current
If a three-phase induction motor is operated under a
light load and it develops an open in one of its supply
lines, the motor will __________.
continue to run, but will vibrate and have reduced torque
If a three-phase induction motor malfunctions and drops
to a single-phase (one supply line open) __________.
the motor will continue to run if it is not heavily loaded
A characteristic of a wound-rotor induction motor, with a
high resistance rotor winding, is __________.
high starting torque
Regarding an induction motor, the power developed by
the rotor automatically adjusts itself to the __________.
power required to drive the load
The synchronous speed of an induction motor is the
__________.
speed of the rotating field
The direction of rotation of an induction motor is
__________.
the same as the direction of the rotating fields
One item listed on the name plate of a cargo pump
motor is ‘degrees centigrade rise.’ This number is based
on __________.
an ambient temperature of 40° C
The rotor of a synchronous motor operates in
synchronism with the rotating field because
__________.
the rotor is magnetically locked into step with the rotating magnetic field by the excitation current
The most common source of excitation for the rotor of a synchronous motor is a/an __________.
DC supply
The purpose of a cage rotor winding placed on the rotor
of a synchronous motor is to __________.
start the machine as an induction motor
