AC Machines Flashcards
referred to as alternators
AC generator
almost all electric power for homes and industries is supplied by this
alternators
consists of constant magnetic field, conductors that rotate across the magnetic field, and some means to connect the conductors as they are rotating
AC generator
Types of Alternator
DC alternator, AC alternator
produces alternating current that is converted to direct current; found on smaller aircraft
DC alternator
produces a great deal of power, typically found on larger aircraft
AC alternator
You can also define an alternator depending on its ______ and ______.
stator, rotor
similar in construction from DC generators; setup is typically found in alternators that have low power rating
Revolving-armature type alternator
has both a stator and a rotor; armature is connected directly to the load without sliding contacts in the load circuit
Revolving-field type alternator
stator is made up of several windings connected in series to form a single circuit
Single-phase alternator
has two or more single phase windings; windings are electrically separated from each other so that one would cut the maximum number of flux lines, and the other one would not cut any
Two-phase alternator
referred to as ‘polyphase alternator’
Three-phase alternator
it has three single-phase windings spaced so that the voltage induced in each windings is ____ out of phase with the voltage in the other two windings
Three-phase alternator, 120 degrees
most powerplant utilize this concept for it allows an increase in power
operating in parallel (paralleling generators)
To parallel two generators, their terminal voltages must be _____, and voltages must be _______, as well as their frequencies must be equal.
equal, in phase
when conditions in parallel generators are met, they are now operating in ______
synchronism
the process of getting the generators into synchronism is called
synchronizing
consists of a frame (yoke) and two end brackets (bearings housing)
enclosure
holds the components together and protects it
enclosure
permits the cooling air to flow through the motor
open enclosure
limits the flow of air into the motor
totally enclosed enclosure
Types of Totally Enclosed Enclosure
totally enclosed non-ventilated enclosure, totally enclosed fan-cooled enclosure, explosion-proof enclosure
2 Main Parts of Stator
stator core, stator windings
an electromagnet when built and current is applied
stator
made up of many thin metal sheets known as laminations
stator core
thin metal sheets making up the stator core
laminations
used to reduce energy losses
stator core
directly connected in the power source
stator windings
rotating part of the electromagnetic circuit
rotor
mounted on the shaft and support the rotor to turn
bearings
metal box on motor which protects one or more terminal boards
conduit box
Two Types of Commutator Motor
AC Series Motor, Repulsion Motor
known as the universal motor
AC series motor
repulsion motor has an armature and commutator similar to that of a dc motor; brushes are not connected to the supply but are short-circuited
repulsion motor
not self-starting; magnetic field set up in the stator by the ac power supply stays lined up in one direction
induction motor
if two stator windings of unequal impedance are spaced 90 degrees apart but connected in parallel to a single-phase source, the filed produced will appear to rotate
Split-Phase Motor
Two Types of Split-Phase Motor
Capacitor Start Motor, Permanent Capacitor Motor
windings connected to a commutator
repulsion start induction motor
a shaded pole is produced by a short-circuited coil wound around a part of each pole of a motor
shaded-pole motor
several types exist to drive electric clocks, phonograph, turntables, and other devices requiring precise rotation
synchronous motor
most used type of AC motor because of its simple, rugged construction, and good operating characteristics
induction motors
laminated core with conductors placed parallel to the shaft
squirrel cage motor
insulated winding similar to the stator winding
wound rotor motor
rotor circuit is excited and have stators that produced rotating magnetic fields
synchronous motors
