Motors and Generators Small DC MotorGenerator in a Hydro PlantGeothermal GeneratorImage courtesy of DOE / NREElectric !ur"ine GeneratorFaraday EfectFaradayEffectBasicConcepts Voltage V Potential to Move Charge (volts) Current I Charge Movement (amperes or amps) Resistance R V = IxR (R in =ohms) Power P = IxV = I2xR (watts) Electric motors and generators#Permanent magnets and electromagnets work together to make electric motors and generators.# The secret is in the ability of an electromagnet to reverse its north and south poles.Electric MotorMElectricalEnergyMechanicalEnergy! Motor! MotorElectromagnetsNSElectromagnet ends change "et$een north and south de%ending on the direction of the current&SNMagnet PolesN SRemem"er that o%%osite %oles attract and li'e %oles re%el&If you alternate the middle magnet(s %oles) it $ill continue to s%in&N S N S N S!his is ho$ motors can turn* Electric motors# "round the edge of a disk are several magnets# their alternating north and south poles facing out.Electric motors#To make the disk spin# you bring a permanent magnet close to its edge. # The free magnet attracts one of the magnets in the disk and repels the ne$t one.The disk is a rotor because it rotates.#%n a working electric motor# an electromagnet replaces the magnet you reversed with your &ngers.#The electromagnet switches its poles to make the rotor keep turning.Electric motorsElectric motors#"s the rotor spins# a commutator reverses the direction of the current in the electromagnet.Electric motorsMotors have three parts'(." rotor with magnets that alternate.).*ne or more fxed magnets around the rotor.+." commutator that switches the direction of current to keep the rotor spinning.Parts of a ,mall ! Motor+rmatureCommutatorPermanentMagnets,rushes-ireConnectionsParts of a -asic ! MotorN SN SDC Source+rmatureCommutator,rushCommutator,rushMotor. + de/ice used to con/ert electric energy into mechanical energy&PermanentMagnetPermanentMagnet-attery run electric motors#"n electric motor that runs from batteries has the same three parts.# The permanent magnets are on the outside# and the electromagnets turn in the rotor.(.-asics of a Electric Motor -attery run electric motors#" simple battery powered motor has three electromagnets in the armature.(/"ction of a !ommutator(0"rmature of a ! Motor(1Generated 2oltage in a ! Machine"! Motors# "! motors can be divided into two main forms'# synchronous motors# induction motors# 3igh4power versions of either type invariably operate from a three-phase supply# but single4phase versions of each are also widely used 5 particularly in a domestic setting"! Motors# Induction motors# these are perhaps the most important form of "! motor# rather than use slip rings to pass current to the &eld coils in the rotor# current is induced in the rotor by transformer action# the stator is similar to that in a synchronous motor# the rotor is simply a set of parallel conductors shorted together at either end by two conducting rings"! Motors#A squirrel-cage induction motor"! Motors# %n a three-phase induction motor the three phases produce a rotating magnetic &eld 6as in a three4phase synchronous motor7# a stationary conductor will see a varying magnetic &eld and this will induce a current# current is induced in the &eld coils in the same way that current is induced in the secondary of a transformer# this current turns the rotor into an electromagnet which is dragged around by the rotating magnetic &eld.%n single-phase induction motors other techni8ues must be used to produce the rotating magnetic &eld.such motors are ine$pensive and are widely used in domestic applications9niversal Motors# :hile most motors operate from either "! or !# some can operate from either# typically operate at high speed 6usually ; (