Test 1
When a load is applied to a 3-phase squirrel cage-motor induction motor, the rotor speed will
decrease slightly
Direct current permanent magnet servo motors are used in cranes to start heavy loads
false
The locked-rotor starting current of an induction motor is several times less than the full-load current.
false
direct current motors can normally operate directly from the power supplied by the electric utility system.
false
the speed of a squirrel-cage motor can be varied by varying the supply?
frequency
A wound - rotor induction motor is normally started with
full external rotor existence
The shunt-type DC motor is know to have
good speed regulation
The series-type DC motor has
high starting torqe
A polyphase synchronous motor is frequently used to
improve power factors
As the load on an induction increases the power factor will
increase
A _________ is an example of a constant horsepower load
lathe
The commutator in a DC motor reverses armature coil current flow to produce continuous armature rotation.
true
The speed of a DC shunt motor is inversely proportional to the field current.
true
the direction of rotation for a 3-phase AC motor can be changed by exchanging L1 and L2 of the supply voltage.
true
the speed of a 3-phase synchronous motor is the same as that of rotating magnetic field
true
A series-type DC motor uses filed coils?
with low resistance made up of a few turns of large diameter wire
DC shunt motor should never be operated
with the field circuit open
a DC series motor runs fast with a light load
True
On a 3-phase motor, the stator windings are arranged to create
a rotating magnetic field
the __________ motor has the highest starting torque of all single phase motors
capacitor start/ capacitor run
the _____________________ motor has the highest starting torque of all the single phase motors
capacitor start/ capacitor run
The purpose of a commutator on a DC motor is
To maintain the proper direction of current flow in the armature conductors.
A good capacitor will hold will hold a charge even when the power is removed.
True
A split-phase motor relies on the start winding to create a phase shift.
True
Overheated bearings may cause motor noise
True
The synchronous speed of a 2-pole, 60hz AC motor is
3600 RPM
Which of the following is not a requirement for motor action?
A source of mechanical energy
TWO basic categories of motors are
AC and DC
A variable AC motor drive is able to operate the motor
ALL the above, (above, at and below base speed)
Shunt field coil wingdings of DC mtors
All the above
The Voltage induced into the armature of a DC motor is known as the
CEMF
An electric motor uses ______________ to operate
Electric Current, Magnetism
A current-carrying conductor, placed in and right angles to a magnetic field, tends to move parallel to the field
False
Single phase operation of a 3-phase motor will reduce the current in the two remaining phases.
False
Unlike 3-phase induction motors, single-phase types are self-starting.
False
Which of the following NEMA insulation classes has the highest safe maxiumum operating temp
NEMA H
If the field current of a shunt-type DC motor is held constant and the armature voltage is increased, as a result,
Speed of the motor will increase
Torque is best defined as
The turning force produced by a motor
Single-phasing refers to the operation of a 3-phase motor on two phases because one phase is lost.
True
the direction of rotation of a 3-phase induction motor is determined by
phase sequence
DC compound motors are used to operate loads that require
relatively constant speed under varying loads
The direction of rotation of a shunt wound DC motor is changed by
reversing the current flow through the armature reversing the current flow through the field
The synchronous speed of an induction motor refers to the speed of the
rotating magnetic field
The universal motor is constructed similar to that of a _________ type DC motor
series
A DC series motor
should never be operated without a LOAD
A squirrel-cage rotor consists of
single bars short circuited by end rings
The direction of rotation on a split-phase motor can be reversed by interchanging the connections to
the run winding, the start winding
One advantage DC type motors have over AC types is that
their speed can be easily varied
A three-phase synchronous motor can produce a leading power factor
true
Compared to a squirrel-cage motor equivalent horsepower, a wound rotor motor has a higher starting torque and lower starting current.
true
