DC motors review
A square wave voltage varies between 0 V and 12 V. The positive pulses are 25μs wide and there is a 75μs gap between them. What is the DC average of the waveform?
3V
armatures are wound to provide high voltage, high current, or some specific combination of current and voltage. Which type of winding provides high voltage and low current?
wave-wound
The motor that does not contain a wound armature, commutator, or brushes is the _____ motor.
brushless DC
Counter-electromotive force (CEMF) and back-EMF are names for the voltage induced into the armature of a DC motor.
true
A series motor may be operated with no load connected
false
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 ____ ride against the commutator segments and are used to connect the armature to the external circuit of the DC machine
brushes
A compound motor has ___ field windings.
Series and shunt
a device that converts electrical energy into mechanical energy is called
a motor
the speed regulation of a DC motor is proportional to the ___
armature resistance
In a compound DC motor control circuit, the field loss relay will disconnect the _____ if power is lost to the _____.
armature; shunt field
What is the component of a DC generator that converts the armature AC into DC?
commutator
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
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 compound generator has both series and shunt windings. When those windings are connected so the aid each other in the production of magnetism, that connection is called ___
cumulative-compound
the compound motor connection that should generally be avoided is the
differential
Series field windings are connected in series with the armature. they are wound with ___ turns of fairly ___ wire
few; large
armatures are wound to provide high voltage, high current, or some specific combination of current and voltage. Which type of winding provides moderate voltage and moderate current?
frogleg-wound
armatures are wound to provide high voltage, high current, or some specific combination of current and voltage. Which type of winding provides low voltage and high current?
lap-wound
Shunt field windings are connected in parallel with the armature. they are wound with ___ turns of fairly ___ wire
many;small
shunt generators contain only a shunt field winding connected in ___ with the armature
parallel
What provides the magnetic field necessary for the operation of a DC machine?
pole pieces
The ServoDisc motor is also often called a _____ motor.
printed-circuit
The speed of the disc servomotor can be varied by changing the amount of voltage supplied to the armature. The voltage is generally varied using _____.
pulse-width
the series generator has only a series field, which is connected in ___ with the armature
series
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
small permanent magnet motors that have lightweight rotors are often used as ___
servo motors
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
What is a device that converts mechanical energy into DC electrical energy?
A generator
The rotating part of a generator is called the
Armature
___ is a measure of the useful electric energy produced by the generator
countertorque
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
The output voltage of a generator is usually controlled by the amount of ___
field excitation current
permanent magnet motors have ___ efficiency than conventional field-wound motors
higher
___ is the twisting or bending of the magnetic lines of flux of the pole pieces.
armature reaction
A square wave voltage varies between 0 V and 12 V. The positive pulses are 50 μs wide and there is a 50 μs gap between them. What is the DC average of the waveform?
6V
A square wave voltage varies between 0 V and 12 V. The positive pulses are 75μs wide and there is a 25μs gap between them. What is the DC average of the waveform?
9V
the servo motor featuring a fiberglass and copper rotor is the ___ motor.
Servodisc