EET 251

Electricity and Electronics

Lesson Seven

ELECTRICAL ENERGY CONVERSION

Electrical energy conversion takes place in all electrical systems. The part of the system where energy is converted to another form is called the load. There are many different types of loads that are part of electrical circuits. A load can be a resistance, inductance, or capacitance as discussed in lesson 6. In this lesson, the function of the load is considered.

Electrical energy is commonly converted to light energy, heat energy, and mechanical energy. Many types of electrical lights are used today. Electrical heating has also become very popular in homes and other buildings. Electrical motors are loads that convert electrical energy into mechanical energy. Several different types of electrical energy conversion will be outlined in this lesson.

7.1 Lighting Systems

Principles of:

(1) Incandescent lighting

(2) Fluorescent lighting

(3) Vapor lighting

Comparison of light sources for efficiency

7.2 Heating Systems

Principles of:

(1) Resistance heating

(2) Induction heating

(3) Dielectric (Capacitive) heating

7.3 Mechanical Loads (Motors)

Basic parts of the motor: stator, rotor and other equipment

Principle of the motor

Torque

Right-hand motor rule

7.4 Direct-Current Motors

Operation of dc motors

Load, speed, counter electromotive force, current, torque

Types of dc motors:

(1) Permanent magnet dc motors

(2) Series-wound dc motors

(3) Shunt-wound dc motors

(4) Compound-wound dc motors

7.5 Three-Phase AC Motors

Principles and operation of:

(1) Three-phase ac induction motor

(2) Three-phase ac synchronous motor

7.6 Single-Phase AC Motors

Principles and operation of:

(1) Universal motors

(2) Induction motors

- split-phase motors

- capacitor motors; capacitor-start or capacitor-run or two-value capacitor

- shaded-pole motors

(3) Single-phase synchonous motors

7.7 Synchro Systems and Servo SystemsSynchro systems, components and functioning

Sc Stepping Motors

7.8 Motor Performance

Efficiency and power factor

Effect of load

Effect of voltage variation on efficiency and power factor

Applications of dc, single-phase ac, three-phase ac systems

7.9 Motor Control Basics

Motor starting control: switches, circuit breakers, motor-starting device, magnetic starter, combination starter, etc.

Criteria for choosing motor controllers

(1) type of motor

(2) motor ratings

(3) motor operating conditions

(4) utility company regulations

(5) type of mechanical load connected to motor

Interpretating data on a motor nameplate

REVIEW

1. How do incandescent, fluorescent and vapor lighting systems differ?

2. How do resistive, inductive, and capacitive heating methods differ?

3. Discuss basic motor action, which is how torque is produced by a motor.

4. What is meant by (a) horsepower and (b) torque?

5. Discuss the following types of motors: (a) permanent magnet, (b) series, (c) shunt, and (d) compound.

6. Discuss the induction principle of single-phase motor operation.

7. How is the speed of an ac motor calculated?

8. Discuss the operation of the following types of ac motors:

a. Universal motor

b. Split-phase motor

c. Capacitor-start, induction motor

d. Shaded-pole motor

e. Single-phase synchonous motor

f. Three-phase induction motor

g. Three-phase synchronous motor

9. How are three-phase synchronous motors commonly started?

10. What are three-phase ac synchronous motor applications