Delmar 11
_______________ is the twisting or bending of the magnetic lines of flux of the pole pieces.
Armature reaction
When a DC machine is used as a generator, the _______________ performs the function of a mechanical rectifier to change the AC produced in the armature into DC before it exits the machine through the brushes.
Commutator
_______________ is a measure of the useful electric energy produced by the generator.
Countertorque
A series motor may be operated with no load connected. True False
F
In a DC motor, terminals A1 and A2 are connected to the shunt fields. True False
F
Some DC generators use electromagnets to provide the magnetic field instead of permanent magnets. T F
F
The simplest method of setting the brushes to the neutral plane position is to connect a DC voltmeter across the series field leads. T F
F
Because brushes are made from a material that is softer than the copper bars of the commutator, this permits the brushes to wear instead of the commutator. True False
T
Converters are used to change the DC into multiphase AC to produce a rotating magnetic field in the stationary armature or stator of the brushless DC motor. T F
T
Counter-electromotive force (CEMF) and back-EMF are names for the voltage induced into the armature of a DC motor. True False
T
DC motors and DC generators use the same terminal identification. T F
T
In a compound DC motor control circuit, the field loss relay will disconnect the _____ if power is lost to the _____. rotor; armature armature; shunt field shunt field; armature armature; rotor
armature; shunt field
The _____ ride against the commutator segments and are used to connect the armature to the external circuit of the DC machine. field windings pole pieces armature windings brushes
brushes
What type of DC motor uses a rotor shaped like a hollow cylinder or cup? three -phase brushless brush -type single- phase
brushless
A generator containing both series and shunt fields is called a _____ generator. self-excited separately excited complex compound
compound
What type of generator is most used by large DC machines? series shunt compound
compound
Because the fields of PM motors are permanent magnets, the field flux remains ________ at all times. constant in flux charged off
constant
A compound generator has both series and shunt field windings. When those windings are connected so their fields oppose each other in the production of magnetism, that connection is called _____. cumulative-compound differential-compound
differential-compound
Series field windings are connected in series with the armature. They are wound with _____ turns of fairly _____ wire. many; large many; small few; large few; small
few; large
Shunt field windings are connected in parallel with the armature. They are wound with _____ turns of fairly _____ wire. many; large few; large many; small few; small
few; small
Armatures are wound to provide high voltage, high current, or some specific combination of voltage and current. Which type of winding provides low voltage and high current? frogleg-wound lap-wound wave-wound
lap-wound
In a compound generator, which connection has the shunt field connected in parallel with both the armature and series field? short shunt long shunt short series long series
long shunt
What is a DC generator that uses permanent magnets as its field? magnetic flux magnetic generator magnetic field magneto
magneto
What are permanent magnets in a PM motor? commutators armatures pole pieces brushes
pole pieces
Which type of generator's amount of output voltage produced is proportional to the number of turns of wire in the armature, the strength of the magnetic field of the pole pieces, and the speed of rotation? series shunt compound
series
A compound motor has _____ field windings. series shunt series and shunt combined
series and shunt
In a generator, the _____ permits part of the current that normally flows through the series field to flow through the resistor. series field shunt rheostat shunt field series rheostat series field exciter shunt field exciter
series field shunt rheostat
Which of the following are used to operate tape drives on computers? permanent magnets servomotors ServoDisc motors printed-circuit motor
servomotors
The DC motor, known as a "constant speed motor," is the _____ motor. series shunt
shunt
What type of generator can be either self-excited or separately excited? series shunt compound
shunt
When the field winding of a DC motor is connected in parallel with the armature, the motor is called a _____ motor. series shunt
shunt
The pushing or turning force created by the magnetic field of the pole pieces and the magnetic field of the loop or armature is called _______________.
Torque
The rotating part of a generator is called the _____. stator field armature exciter
armature
A compound generator has both series and shunt field windings. When those windings are connected so they aid each other in the production of magnetism, that connection is called _____. cumulative-compound differential-compound
cumulative-compound
The output voltage of a generator is usually controlled by the amount of _____. field excitation current input voltage input torque armature excitation current
field excitation current
Armatures are wound to provide high voltage, high current, or some specific combination of voltage and current. Which type of winding provides high voltage and low current? frogleg-wound lap-wound wave-wound
wave-wound
There may be occasions when one DC generator cannot supply enough current to operate the connected load. When this occurs, another generator is connected in series with the first. True False
F
Direct current motors that contain permanent magnet field poles are more efficient because no power is required to produce the magnetic fields of the pole pieces. T F
T
Flashing the field results in polarity of the output voltage being reversed when the machine is restarted as a generator. T F
T
Most DC machines are designed in such a manner that the position of the brushes on the commutator can be set or adjusted. T F
T
Motors with a large amount of inertia exhibit superior speed-regulation characteristics. T F
T
The terminal leads of DC machines are labeled so they can be identified when they are brought outside the motor housing to the terminal box. T F
T
When using the right-hand motor rule, the center finger indicates the direction of armature current. T F
T
When a motor is connected as a differential compound, the _____ determines the direction of rotation of the motor at no load or light load. shunt field armature rotor load
shunt field
The voltage produced in all rotating armatures is alternating voltage. T F
T
