1. BEX – Basic Electricity – Unit 13 Magnetic Motors REF: Delmar’s Standard Textbook of Electricity, Unit 13

2. Magnetic Motors Lesson Objectives: To understand the principles of magnetism as it applies to magnetic motors To identify the different types of motors To identify the various components of an electromagnetic motor

3. Magnetic Motors Magnetic properties Unlike poles attract Like poles repel The basis for the operation for a motor

4. Magnetic Motors Magnetic properties Current flow through a conductor creates a weak magnetic field Wrapping a conductor increases the magnetic field

5. Magnetic Motors Magnetic Properties When 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

6. Magnetic Motors Components

7. Magnetic Motors A Simple Electromagnetic Motor Armature windings Field windings Pole shoes Brushes Commutator Power source

8. Magnetic Motors Field Coils & Pole Shoes: Heavy copper wire wrapped in a coil Surrounding an iron core Forms an electromagnet

9. Magnetic Motors The Armature: Rotates within stationary field coils Consists of heavy loops of insulated copper wire Wraps around (and insulated from) a laminated iron core

10. Magnetic Motors The Commutator: A series of split ring copper segment bars Forms a sliding contact area for brushes

11. Magnetic Motors The Brushes: Made of a mixture of carbon and copper Used to conduct high amperage through armature windings

12. Magnetic Motors Conductor/Field Coil Interaction: Magnetic fields react by moving the conductor towards the weaker magnetic field Armature rotates energizing the next contact on the commutator

13. Magnetic Motors Counter Electromotive Force (CEMF): Produced by electromagnetic induction in the windings Tends to act against the supply voltage Increases with motor speed Reduces current/torque of motor

14. Magnetic Motors Types of motors

15. Magnetic Motors Series Wound: Current flows through the field windings Then through the armature windings Returns to ground Maximum torque is developed during initial start up CEMF increases with motor speed

16. Magnetic Motors Parallel Wound: Current flows in parallel to the field windings, positive brushes and commutator, armature, and grounding brushes A low torque motor Spins at lower speeds CEMF does not increase with motor speed

17. Magnetic Motors Compound Wound: Most of the field coils are in series to the armature One field coil is connected to ground Combines the best properties of the series and the parallel wound motors Motor has good initial torque and speed

18. Magnetic Motors Permanent Magnet Motor: Electromagnetic field coils are replaced with permanent magnets Reduces the size and weight of motor Uses less current

19. 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.

20. 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?

21. Elizabethtown Technical College Basic Electricity BEXS100/101 Text: Delmar’s Standard Textbook of Electricity Magnetic Motors