1. Chapter 9
Basic Electric Motors

2. Objectives Upon completion of this course, you will be able to:
Explain magnetism and the part it plays in the operation of electric motors
Explain torque and the purpose of different types of single-phase motors
Explain the operation of a basic electric motor

3. Objectives (cont’d.)
Understand how to operate, install, reverse the rotation (if possible), and diagnose problems in a shaded-pole motor
Understand the purpose of capacitors in the operation of a single-phase motor and be able to explain the difference between a starting and running capacitor

4. Objectives (cont’d.)
Correctly diagnose the condition of any capacitor and, using capacitor rules, be able to substitute a capacitor if a direct replacement is not available
Explain how to operate, install, troubleshoot, and repair (if possible) split-phase and capacitor-start motors

5. Objectives (cont’d.)
Explain how to operate, install, troubleshoot, and repair (if possible) permanent split-capacitor motors
Explain how to operate, install, troubleshoot, and repair (if possible) capacitor-start–capacitor-run motors
Understand how to operate, install, reverse, and troubleshoot three-phase motors

6. Objectives (cont’d.)
Explain how to operate, install, troubleshoot, and repair (if possible) electronically commutated motors
Identify the common, start, and run terminals of a single-phase compressor motor

7. Key Terms Capacitor Capacitor-start motor
Capacitor-start-capacitor-run motor
Delta winding
Electromagnet
Electronically commutated motor (ECM)
Flux
Hermetic compressor
Induced magnetism

8. Key Terms (cont’d.) Magnetic field Magnetism Microfarad
Permanent magnet
Permanent split-capacitor motor
Rotor
Running capacitor
Shaded-pole motor
Split-phase motor
Squirrel cage rotor
Star winding

9. Key Terms (cont’d.)
Starting capacitor
Stator
Three-phase motor
Torque

10. Introduction Electric motors
Change electric energy into mechanical energy
Used to drive any device needing energy to power its movement
Many types
Torque: strength the motor produces by turning

11. Magnetism Physical phenomenon Produced in many different ways
Includes attraction of an object for iron
Exhibited by a permanent magnet or electric current
Produced in many different ways
Example: magnetic fields of the earth
Compass reaction to earth’s magnetic fields

12. Magnetism (cont’d.) Magnets have two poles: north and south
North pole of a bar magnet is brought close to north pole of another bar magnet
They will repel
South pole of a bar magnet is brought close to the north pole of bar magnet
They will attract each other

13. Magnetic Field Flux Magnetic field
Magnetic lines of force of a magnet that flow between the north and south poles
Magnetic field
Area that the magnetic force operates in
Can flow through material

14. Induced Magnetism
Created when a piece of iron is placed in a magnetic field
The closer an object is to the magnet, the stronger the magnetic field
Figure 9.5 Magnetic field of an iron core
when a current-carrying conductor
is wound around the core.
(Delmar/Cengage Learning)

15. Induced Magnetism (cont’d.)
Permanent magnet
Magnetic material that has been magnetized
Can hold magnetic strength
Electromagnet
Magnet produced through electricity
Electron flow is in a conductor
Magnetic field is created around the conductor

16. Basic Electric Motors
Create a rotating motion and drive components that need to be turned
Electric energy is changed to mechanical energy by magnetism
Based on induced magnetism
To make an electric motor rotation continuous the magnet field must rotate

17. Types of Electric Motors
All kinds of AC motors are used to rotate many different devices
Different motors are needed
Not all motors have the same running and starting characteristics
Must use the right motor for the right job

18. Motor Strength Generally used to classify motors
Motors are selected mainly because of starting torque required
General types of motors
Shaded-pole, split-phase, permanent split- capacitor, capacitor-start-capacitor-run, capacitor-start, three-phase, and electronically commutated

19. Motor Speed Formula Common motor speeds Motor with a load
Speed = (Flow reversals/second x 120)/ Number of poles
Common motor speeds
Two-pole: 3450 rpm
Four-pole: 1750 rpm
Six-pole: 1050 rpm
Eight-pole: 900 rpm

20. Open and Enclosed Motors
Open motors
Have a housing
Rotate a device not enclosed in housing
Enclosed motors
Housed within some type of shell
Most common enclosure: completely sealed hermetic compressor

21. Motor Dimensions
Established by National Electrical Manufacturers’ Association (NEMA)
Figure 9.14 Dimension of typical motor frames. (Delmar/Cengage Learning)

22. Shaded-Pole Motors
Used when very small starting and running torques are required
Operation: current is induced into shaded pole from main windings
Reversing: requires disassembly
Troubleshooting: easy to identify because of the copper band around shaded pole

23. Capacitors
Consist of two aluminum plates with an insulator between them
Two types used in the industry
Electrolytic or starting capacitor
Oil-filled or running capacitor
Troubleshooting: short capacitor life and malfunctions
Caused by several different factors

24. Split-Phase Motors Two general classifications:
Resistance-start-induction-run motor
Capacitor-start-induction-run motor
Each has different operating characteristics
Similar construction
Use some method of splitting the phase of incoming power to produce a second phase

25. Resistance-Start-Induction-Run Motors
Have starting and running winding
Most have some method of beginning rotation
Operation: phases are split by makeup of starting windings
Troubleshooting: probable areas are the bearings, windings, and centrifugal switch

26. Capacitor-Start-Induction-Run Motors
Produce a high starting torque
Needed for many applications
Operate like a split-phase motor
Except a capacitor is inserted in series with centrifugal switch and starting windings
Types
Open and enclosed

27. Permanent Split-Capacitor Motors
Simple design and moderate starting torque
Operation: running capacitor is put in series with starting winding
Troubleshooting: usually trouble-free for long periods
Common failures: bearings, windings, and capacitor

28. Capacitor-Start-Capacitor-Run Motors
Produce high starting torque and increase running efficiency
Operation: begin on a phase displacement between starting and running windings
Troubleshooting: sometimes difficult
Number of added components

29. Three-Phase Motors Rugged, reliable, and more dependable
Most common: squirrel cage induction type
Operation: same principles as single-phase
Except three-phase displacement
Troubleshooting: ohmmeter is used to check resistance

30. Electronically Commutated Motors
Reverse one-half of each AC cycle to form a single directional current
Construction: brushless DC, three-phase motor with a permanent magnet rotor
Two part motor: motor and control
Operation: determined by control inputs
Troubleshooting: difficult
Various interfaces, strategies, and modules

31. Hermetic Compressor Motors
Induction type motors
Designed for single- and three-phase current
Operation: enclosed in a shell with refrigerant and oil
Requires special considerations
Terminal identification: common, start, and run terminals
Troubleshooting: often difficult

32. Service Call Protocol
Many types of service procedures are performed each day
Pre-season startups
Preventive maintenance calls
Inoperative system calls
Technicians
Must always keep in mind the need for service calls