1022 Year end review - Theory
Armatures are wound to provide high voltage, high current or some specific combination of voltage and current. Which type of winding provides moderate voltage and moderate current?
Frogleg-wound
Permanent magnet motors have _____ efficiency than conventional field-wound motors.
Higher
A compound motor has _____ field windings.
Series and Shunt
Small permanent magnet motors that have lightweight rotors are often used as _____.
Servomotors
The DC motor, known as a "constant speed motor," is the _____ motor.
Shunt
When the field winding of a DC motor is connected in parallel with the armature, the motor is called a _____ motor.
Shunt
When a motor is connected differential compound, the _____ determines the direction of rotation of the motor at no load or light load.
Shunt Field
The squirrel-cage rotor code letters indicate the shape (type) of rotor bars. Different types of bars have a large effect on the _____ of a motor.
Starting Torque
The rotating part of a generator is called the _____.
Armature
The _____ ride against the commutator segments and are used to connect the armature to the external circuit of the DC machine.
Brushes
In three-phase power systems, the delivered power _____.
Never falls to zero
When calculating the power of a pure resistive load, the voltage and current are in phase with each other and the power factor is _____.
One
Conductive compensation is accomplished by connecting the compensating winding in _____ with the armature.
Series
The series generator has only a series field, which is connected in _____ with the armature.
Series
The _____ motor can operate on either AC or DC voltage.
Universal
The set of squirrel-cage bars on the rotor of a synchronous motor is used to start the motor and is known as the _____.
amortisseur winding
The output shaft of a stepping motor _____.
moves through a specific angle for each input pulse
A delta-connected set of windings has a phase current of 10 A. What is the line current?
17.32 A
A motor is operating at 3450 RPM and is producing a torque of 32 lb-in. What is the output horsepower of the motor?
1.75 HP
Line voltage and phase voltage are the same in the _____ connection.
Delta
A delta connected set of windings has a phase voltage of 100 V. What is the line voltage?
100 V
Three-phase voltages are _____ out of phase with each other.
120°
A delta-connected three-phase alternator is driving a wye-connected resistive load. The alternator output voltage is 480 V. The load resistors are 12 Ω each. What is the phase current in the alternator?
13.33 A
The horsepower rating of three-phase motors and the kilovolt-ampere rating of three-phase transformers are about _____ greater than for single-phase motors or transformers with a similar frame size.
150 Percent
A wye-connected alternator that has phase voltages of 277 V is feeding two loads. The first load is wye-connected inductors that have 40 Ω of XL. The second load is delta-connected capacitors that have XC of 60 Ω. How much is the alternator phase current?
6.93 A
In a balanced three-phase system, the conductors need be only about _____ the size of conductors for a single-phase, two-wire system of the same kilovolt-ampere (kVA) rating.
75 Percent
What is a device that converts mechanical energy into DC electrical energy?
A Generator
The speed regulation of a DC motor is proportional to the _____.
Armature resistance
The motor that does not contain a wound armature, commutator, or brushes is the _____ motor.
Brushless DC
What is the component of a DC generator that converts the armature AC into DC?
Commutator
The universal motor has a wound armature and brushes like an AC motor, as well as an added component, the _____.
Compensating Winding
A generator containing both series and shunt fields is called a _____ generator.
Compound
The relationship of the strengths of the two fields in a generator determines the amount of _____.
Compounding
A three-phase connection in which three separate inductive loads have been connected together is a(n) _____ connection.
Delta
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 _____.
Differential-Compound
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?
Lap-Wound
In a three-phase connection, what is the voltage measured between the lines?
Line Voltage
A device that converts electrical energy into mechanical energy is called a(n) _____.
Motor
Shunt generators contain only a shunt field winding connected in _____ with the armature.
Parallel
In a three-phase connection, what is the voltage measured across a single winding?
Phase voltage
What provide(s) the magnetic field necessary for the operation of a DC machine?
Pole Pieces
A(n) _____ motor operates on the principle that like magnetic poles repel.
Repulsion
Three lines supply power to a three-phase motor. If one of these lines should open, the motor will be connected to single-phase power. This condition is known as _____.
Single Phasing
In a wye-connected system, the line voltage is higher than the phase voltage by a factor of _____.
Square root of three
The _____ winding is made of many turns of small wire and is located at the top of the stator core of a split-phase motor.
Start
If a three-phase load is a pure reactive load, then the power calculated has units of _____.
VARs
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?
Wave-wound
Line current and phase current are the same in the _____ configuration.
Wye
In single-phase motors such as the resistance start induction-run motor, the start winding is disconnected by the _____.
centrifugal switch
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
Series field windings are connected in series with the armature. They are wound with _____ turns of fairly _____ wire.
few; large
The output voltage of a generator is usually controlled by the amount of _____.
field excitation current
Multispeed fan motors achieve multiple speeds by inserting additional _____ in series with the run winding.
inductance
The alternator must supply the _____ for each of the loads.
line current
Shunt field windings are connected in parallel with the armature. They are wound with _____ turns of fairly _____ wire.
many; small
The _____ winding is made of a few turns of large wire and is located at the bottom of the stator core of a split-phase motor.
run
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
Split-phase motors operate on the principle of a _____ magnetic field.
rotating
Selsyn motors operate on _____ voltage.
Sigle Phase
