TLE Basic Electronics - AC Electronics

AC Electronics

What you are expected to learn

At the end of this module, you should be able to:

Describe how an AC voltage is produced with an AC generator (alternator).
Define alternation, cycle, hertz, sine wave, period, and frequency.
Identify the parts of an AC generator (alternator).
Define peak, peak-to-peak, effective, and rms.
Explain the relationship between time and frequency.
Identify and describe three basic nonsinusoidal waveforms.
Describe how nonsinusoidal waveforms consist of the fundamental frequency and harmonics.
Understand why AC is used in today’s society.
Describe how an AC distribution system works.
Describe how a transformer operates.
Explain how transformers are rated.
Explain how transformers operate in a circuit.
Describe the differences between step-up, step-down, and isolation transformers.
Describe how the ratio of the voltage, current, and number of turns are related with a transformer.
Describe applications of a transformer.
Identify different types of transformers.

How to learn from this module

Going through this module can be both a fun and a meaningful learning experience. All you need to do is make use of your time and resources efficiently. To do this, here are some

tips for you:

1. Take time in reading and understanding each lesson. It is better to be slow but sure than to hurry finishing the module only to find out that you missed the concepts you are supposed to learn.

2. Do not jump from one chapter to another. Usually, the lessons are arranged such that one is built upon another, hence an understanding of the first is essential in comprehending the succeeding lessons.

3. Be honest. When answering the test items, do not turn to the key to correction page unless you are done. Likewise, when performing experiments, record only what you have really observed.

4. Safety first. Perform the experiments with extra precaution. Wear safety gears whenever necessary.

5. Don’t hesitate to ask. If you need to clarify something, approach your teacher or any knowledgeable person.

What to do before (Pretest)

AC Current Flow

Alternating Current is the most commonly used type of electricity.
AC consists of current flowing in one direction and then reversing and flowing in the opposite direction.
One revolution of an AC generator is called a cycle.
The two halves of a cycle are referred to as alternations.
Two complete alternations with no reference to time make up a cycle.
One cycle per second is defined as a hertz.
The waveform produced by an AC generator is called a sinusoidal waveform or sine wave.
The peak value of a sine wave is the absolute value of the point on the waveform with the greatest amplitude.
The peak-to-peak value is the vertical distance from one peak to the other peak.
The effective value of AC is the amount of current that produces the same degree of heat in a given resistance as an equal amount of direct current.
The effective value can be determined by a mathematical process called the rootmean- square (rms) process.
The rms value of a sine wave is equal to 0.707 times the peak value.
Erms = 0.707Ep
Irms = 0.707Ip
The time required to complete one cycle of a sine wave is called the period (t).
The number of cycles occurring in a specific period of time is called frequency (f).
The relationship between frequency and period is:
f=I/t
Square waves are composed of the fundamental frequency and all odd harmonics.
Triangular waveforms are composed of the fundamental frequency and all odd harmonics 180 degrees out of phase with the fundamental frequency.
Sawtooth waveforms are composed of both even and odd harmonics, the even harmonics being 180 degrees out of phase with the odd harmonics.

Sine Wave Simulation Activity

Transformer

A transformer consists of two coils, a primary winding and a secondary winding.
An AC voltage is put across the primary winding, inducing a voltage in the secondary winding.
Transformers allow an AC signal to be transferred from one circuit to another.
Transformers allow stepping up, stepping down, or passing the signal unchanged.
Transformers are designed to operate at certain frequencies.
Transformers are rated in volt-amperes (VA).
The turns ratio determines whether a transformer is used to step up, step down, or pass voltage unchanged.
turns ratio = Ns/Np
The ratio of secondary to primary voltage is equal to the ratio of secondary to primary turns.
Es/Ep = Ns/Np
A transformer that produces a secondary voltage greater than its primary voltage is called a step-up transformer.
The turns ratio of a step-up transformer is always greater than 1.
A transformer that produces a secondary voltage less than its primary voltage is called a step-down transformer.
The turns ratio of a step-down transformer is always less than 1.
The amount the voltage is stepped up or down is determined by the turns ratio.
Transformer applications include: impedance matching, phase shifting, isolation, blocking DC while passing AC, and producing several signals at different voltage levels.
An isolation transformer passes the signal unchanged.
An isolation transformer is used to prevent electric shocks.
An autotransformer is used to step up or step down voltage.
An autotransformer is a special transformer that does not provide isolation.