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R.N.G.P.I.T, Bardoli �Electrical Engineering Department

Subject: BEE

Prepared By:

Dr. Shaikh Mohammed Suhel

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Prepared By:

Name: Dr. Shaikh Mohammed Suhel

(Assistant Professor RNGPIT, Surat)

Former Assistant Professor in SCET, SNPIT&RC, VIT
Qualification: PhD (Power- Electronics & Drives, NIT, Surat), M.Tech (Industrial Electronics, NIT-Surat), Gate, B.E. (Electrical Engineering., VNSGU-Surat).
Experience: 13 Years.

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CH: Introduction to AC Circuits

This Lecture contain
Theoretical concept of AC Sinusoidal waveforms
Representation of sinusoidal waveforms

Target audience
Beneficial for: Undergraduate and diploma student of all branches for their semester examination. Also helpful for GATE and other competitive exams and Interview.

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Introduction

DC Current

Introduction

AC Current

I

Time

I

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Application

DC Source:

Low Power

Application

AC Source:

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Problem associated with DC Supply

Why Low Power?

P=VI, So V need to increase

Load demands Low power, Transformer cannot use in DC Supply system.

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Problem associated with DC Supply

DC Motor has commutator

Cost, maintenance

AC motor

Low cost, rugged, and Low maintenance

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Problem associated with DC Supply

Circuit breaker

Low cost and simpler AC breaker

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Time

I

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Why Sinusoidal voltage?

R, L, C : After many integration and differentiation it remain same

Iron Losses are less
Disturbances are less

Smoothest wave out of all waves

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Sinusoidal function terminology:

Cycle: complete set of +ve & -ve values of a.c quantities.

Time period: Time taken by a.c quantities to complete one cycle.

Maximum or peak value: It is maximum +ve or -ve value called amplitude

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Instantaneous value: It is the value at any instant

Frequency: It is the no. of cycle completed in one second.

Angular frequency: In one sec rad covered by signal.

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Phase: It is the fraction of time period (or) cycle that has elapsed since it has last passed from the chosen zero position.

Phase angle:

Phase difference:

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Average or (mean) value:
It is defined as the steady current that sends the same charge through a circuit in the same time period as the alternating current does in half of its time period

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The charge passing in time dt is:

Charge passing in time T/2 is :

Charge transfer in case of dc:

Average value:

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Average or (mean) value of sine wave:

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Root mean square (RMS) value:
It is given by the steady current that produces same heating effect in a resistance in a given time as the alternating current does in the same resistor in the same time period

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The heat produce in time dt is:

Heat produce in time T/2 is :

So,

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Form factor (FF):
The ratio of RMS value to mean value of alternating quantity is called form factor.

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Peak (or) Amplitude (or)Crest factor:
The ratio of maximum value to rms value of alternating quantity is called peak factor.

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Determine peak, average, rms and form factor of the saw tooth wave shown in Figure.
Solution:

100

0

2

4

6

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Solution(contd.):

100

0

2

4

6

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End

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THANK YOU