DC Machines Flashcards
generators are electrical components that convert mechanical energy to electrical energy through
electromagnetic conduction
supplies the needed electrical energy
generators
2 Types of Generator
DC Generator, AC Generator
DC generator is also known as
Dynamo
a generator that converts the alternating current to a direct current using a commutator
DC generator
What is the current flow of a DC generator?
unidirectional
AC generator is also known as
alternators
a generator that converts mechanical energy to electrical energy in the form of alternating current
AC generator
What is the current flow of an AC generator?
reverse
Who demonstrated that a magnetic field could create current flow?
English scientist Michael Faraday
magnetic field creating current flow is demonstrated by several turns of wire wrapped around a cardboard tube, and the ends of the conductor are connected to a ______
galvanometer
When a magnet is at rest inside the tube, the galvanometer shows a reading of ____
zero
When the bar magnet is moved through the tube, the galvanometer ______
deflects from the zero position
can be created by an armature coil with a single turn of wire
DC generator
When the armature coil cuts across the magnetic field, it produces _____
voltage
When a _______ path is present, current will move through the circuit.
complete
allows both brushes to have contact with the portion of the loop that moves upward and downward
commutator
outer frame of a DC generator; made up of cast iron/steel
yoke or field frame
carries the magnetic flux produced by the field winding
yoke or field frame
the magnetizing force inside a generator
pole/pole shoe/field pole
the core of the electromagnet
pole/pole shoe/field pole
support field coils and spread out the flux in air gap
pole/pole shoe/field pole
wire of the electromagnet; goes together with the pole
field winding or field coil
composed of many turns of wire; produces the flux cut by the armature
field winding or field coil
consists of the armature core, armature coils/armature windings, commutator
armature assembly
rotor of a generator, mounted on a shaft that rotates in bearings located in the generator’s end frames; acts as a conductor when it is rotated
armature core
former wound copper coil which rests in armature slots; can be wounded through 2 methods
armature coil or armature winding
Two Methods of Wounding of Armature Coil/Winding
Lap Winding, Wave Winding
one end of a single armature coil attaches to one commutator segment, while the other end is soldered to the adjacent segment
Lap Winding
a method for stabilizing the armature magnetic field
Lap Winding
Types of Lap Winding
Simplex, Duplex, Triplex
ends of each coil are connected to adjacent commutator segments; all the coils are connected in series
simplex
there are in effect two separate sets of coils, each set connected in series; two sets of coils are connected to each other, only by the brushes
duplex
in effect three separate sets of series-connected coils
triplex
ends of each coil are connected to commutator segments two pole spans apart
wave winding
used to convert the alternating current flowing in its armature into the direct current at its terminals
commutator
ride on the surface of the commutator and act as the electrical contact between armature coils and an external circuit
brushes
a flexible braided-copper inductor which connects each brush to the external circuit
pig tail
generator field’s coils are energized from an external source
separately excited
the generator supplies its own excitation
self-excited
where the field winding is in series with armature winding
series wound
where the field winding is in parallel with armature winding
shunt-wound
combination of series and shunt winding; usually used more often
compound-wound
when the shunt field is parallel only with the armature
short-shunt
when the shunt field is in parallel with both the armature and series field
long-shunt
used to carry the field winding and poles; hollow cylinder which works together with the rotor to constitute magnetic circuit
stator
its function is to develop turning effort, or torque, to produce mechanical rotation
DC motor
used to carry armature winding; cylindrical in shape
rotor
load carrying member of the rotor; a continuous winding, without a beginning or an end
armature winding
rotates in the magnetic field and is composed of numerous coils in series
armature winding
an exciting system which may be an electrical winding or a permanent magnet; located on the stator
field winding
rotates with the rotor and serves to rectify the induced voltage and the current in the armature, both of which area alternating current
commutator
conducting carbon graphite spring loaded to ride in the commutator and act as interface between the external circuit and the armature winding
brushes
provided to place field winding; number of poles is determined by the voltage and current ratings of the machine
poles
a magnetic material used for mechanical support and protection
slot or teeth
supports the iron core, brushes, and the bearings
motor housing
starting twist or force that produces rotation in a motor; rotation necessary for starting a motor
torque
Types of Torque
full-load torque, pull-up torque, breakdown torque, locked-rotor torque
necessary to produce its rated horsepower at full-load speed
full-load torque
aids to bring motor up to rated speed
pull-up torque
maximum torque the motor will develop
breakdown torque
develop when full power is applied when rotor is stationary; the starting twist to get the rotor running
locked-rotor torque
most common type of torque
locked-rotor torque
Motor Types
Shunt Motor, Series Motor, Compound Motor
most common type of DC motor
shunt motor
connected in the same way as shunt generator
shunt motor
most ideal for practical uses
shunt motor
one of the traditional ‘work-horses’ or electromechanical energy transition
series motor
combines the operating characteristics of the shunt and series motors
compound motor
motor may be operated safely at no load
compound motor
as load is added, its speed decreases, and torque is greater compared with that of a shunt motor
compound motor
