ELECTRIC GENERATORS AND MOTORS
list two advantages of Alternating Current
-transformer operation (essential in x ray equipment) -power loss when transmitted over long distances
wave form with two commutator segments results in
100% ripple, and wave from sent to the loads
what is the percentage ripple in a single DC generator
100% ripple, the current goes from minimum to maximum back to minimum (0-100)
a 3 phase pulse is produced
120 degrees after the prior wave
what are the two types of electric motors
AC motor DC motor
to induce electric current in a circuit some parts of the circuit must be changing in the magnetic field
EMI
power loss/heat loss formula
P= I2R
describe a solenoid
a coil of wire with current flowing through it
Faraday's law requires
a conductor a magnetic field relative motion b/w the magnetic field and conductor
explain the principle of a electric motor
a current carrying conductor will be placed in the magnetic field, there will be a force trying to push the conductor out/upward the magnetic field because it distorting it (bending it)
describe a commutator
a metal slip ring divided into 2 pieces white and black ring that reverses the current flow
describe a electromagnet
a solenoid with a iron rod
describe a current carrying conductor
a wire that has current flowing through it
in a AC motor induction why does voltage have to be induced into the rotor via EMI, causing the rotor to rotate/turn
because there's no power is being supplied to rotor, it has no slip rings, brushes, commutators, no physical electrical connection
what makes a DC generator different from a AC
commutator and brushes on external circuit
DC motor uses
commutators
Define electric generators (dynamo)
converts mechanical energy into electrical energy by using EMI
AC motor induction the rotor is ________ bars around ______ that looks like a squirrel cage
copper, iron core
Alternating Current
current is changing directions constantly through the external circuit (loads)
for the right hand rule the middle finger
direction of current flow
for the right hand rule the thumb
direction of motion of the conductor with the respect to the magnetic field
for the right hand rule the index finger
direction of the magnetic field (N to S)
define cycle
from the start from one wave to the start of next consecutive wave
where does AC and DC produce current?
inside of the machine
wave form with multiple commutator segments results in
less ripple in the wave form sent to the loads
the simple electric generator consists of
magnetic field (electromagnet/stator), armature (rotor), slip rings, brushes, external circuit,
reversal of the conductors in the _________, leads to the reversal of the polarity of the ____________ (current flow changes direction) then leads to reversal of _________ flow that results in ______
magnetic field, induced voltage, current, AC
define ferequency
number of cycles per time hour/day/week etc
AC synchronous motor
occurring at the same time, current is applied to both armature (rotor) and the powerful electromagnet (stator) from the same source (same frequency)
alternations/impulses; 2 per cycle is
one positive and one negative 120 sec with 60 Hz
with a AC induction motor the current is only supplied to the
powerful electromagnet (stator)
a motor _______ energy
receives
direction of motion (rotation) of the conductor is determined by the ________________
right hand rule for motors
AC synchronous motor rotates at the same speed with ________
rotor of the generator supplying it generator speed = 3600rpm motor speed=3600rpm
AC synchronous motor uses
slip rings
a AC generator has
slip rings and brushes on external circuit
the powerful electromagnet (stator)
stationary portion field magnet that produces a magnetic field
a generator _________ energy
supplies
AC Motor has two different types
synchronous and induction
what is ripple?
the amount of curvature in the wave
define electric motors
the conversion of electrical energy to mechanical energy
what is motor action? (how a motor works)
the interaction of two magnetic fields
both electric motors and electric generators are the same except for what in electric motors?
the power is being supplied to the motor itself, power is going in
what are the two main parts of a generator
the powerful electromagnet (stator) and the armature (rotor)
the armature (rotor)
the rotating portion, many turns of wire rotated in the magnetic field which is set up by the field magnet
list four ways mechanical energy for rotation can be supplied
turbine electric motor engine (gas or diesel) wind power
peak values (P)
values of V or I at the peak of the curves
