BEX – Basic Electricity – Unit 13

Magnetic MotorsREF: Delmar’s Standard Textbook of Electricity, Unit 13

Magnetic Motors

Lesson Objectives:To understand the principles of magnetism as it applies to magnetic motorsTo identify the different types of motorsTo identify the various components of an electromagnetic motor

Magnetic MotorsMagnetic properties

Unlike poles attractLike poles repelThe basis for the operation for a motor

Magnetic MotorsMagnetic properties

Current flow through a conductor creates a weak magnetic fieldWrapping a conductor increases the magnetic field

Magnetic Motors

Magnetic PropertiesWhen a current carrying conductor is placed inside of a magnetic field, the conductor moves towards the weaker magnetic field on the outside of the magnet

Magnetic Motors

Components

Magnetic MotorsA Simple Electromagnetic Motor

Armature windingsField windingsPole shoesBrushesCommutatorPower source

Magnetic Motors

Field Coils & Pole Shoes:Heavy copper wire wrapped in a coilSurrounding an iron coreForms an electromagnet

Magnetic Motors

The Armature:Rotates within stationary field coilsConsists of heavy loops of insulated copper wireWraps around (and insulated from) a laminated iron core

Magnetic Motors

The Commutator:A series of split ring copper segment barsForms a sliding contact area for brushes

Magnetic Motors

The Brushes:Made of a mixture of carbon and copperUsed to conduct high amperage through armature windings

Magnetic Motors

Conductor/Field Coil Interaction:Magnetic fields react by moving the conductor towards the weaker magnetic fieldArmature rotates energizing the next contact on the commutator

Magnetic Motors

Counter Electromotive Force (CEMF):Produced by electromagnetic induction in the windingsTends to act against the supply voltageIncreases with motor speedReduces current/torque of motor

Magnetic Motors

Types of motors

Magnetic MotorsSeries Wound:Current flows through the field windingsThen through the armature windingsReturns to groundMaximum torque is developed during initial start upCEMF increases with motor speed

Magnetic Motors

Parallel Wound:Current flows in parallel to the field windings, positive brushes and commutator, armature, and grounding brushesA low torque motorSpins at lower speedsCEMF does not increase with motor speed

Magnetic MotorsCompound Wound:Most of the field coils are in series to the armatureOne field coil is connected to groundCombines the best properties of the series and the parallel wound motorsMotor has good initial torque and speed

Magnetic MotorsPermanent Magnet Motor:Electromagnetic field coils are replaced with permanent magnetsReduces the size and weight of motorUses less current

REVIEW…..

HOW DOES A MOTOR USE MAGNETISM?HOW IS ELECTRICAL ENERGY CONVERTED INTO MECHANICAL ENERGY?

WHAT IS THE MOVEABLE, INTERNAL FIELD CALLED?WHAT IS THE STATIONARY OUTSIDE FIELD CALLED?NAME THREE WAYS OF CONNECTING THE 2 FIELDS ELECTRICALLY.

REVIEW….

WHAT IS COUNTER ELECTROMOTIVE FORCE?HOW DOES THE INTERNAL FIELD GETS IT’S POWER AND GROUND?HOW IS A TYPICAL STARTER MOTOR GROUNDED?

HOW IS A PERMANENT MAGNET STARTER DIFFERENT FROM ELECTROMAGNET STARTER?WHAT EFFECT DO THE POLE SHOES HAVE?

Elizabethtown Technical CollegeElizabethtown Technical CollegeBasic Electricity BEXS100/101Basic Electricity BEXS100/101Text: Text: Delmar’s Standard Textbook of ElectricityDelmar’s Standard Textbook of ElectricityMagnetic MotorsMagnetic Motors