21-02-2012, 04:07 PM
Development of Power Factor Controller using PIC Microcontroller
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This thesis contains six chapters each having its own importance. First chapter
contains the all detailed information about the power factor and its correction methods
especially the capacitor correction methods. Second chapter described the hardware
and its configuration. Third chapter embodies software development module, which is
the base of this thesis. Next chapter is related with the control scheme. Result and
discussion along the conclusion and future scope are given in the last two chapters.
Many references are taken in consideration before summarizing the thesis. These
references along with the appendix having details of software is given at the end of
this thesis.
Introduction
Power factor is the ratio of true power or watts to apparent power or volt amps.
They are identical only when current and voltage are in phase then the power factor is
1.0. The power in an ac circuit is very seldom equal to the direct product of the volts
and amperes. In order to find the power of a single phase ac circuit the product of
volts and amperes must be multiplied by the power factor. Ammeters and voltmeters
indicate the effective value of amps and volts. True power or watts can be measured
with a wattmeter. If the true power is 1870 watts and the volt amp reading is 2200.
Than the power factor is 0.85 or 85 percent. True power divided by apparent power.
Introduction to power factor
For a DC circuit the power is P=VI and this relationship also holds for the
instantaneous power in an AC circuit. However, the average power in an AC circuit
expressed in terms of the rms voltage and current is
Pavg = VI cosφ
Average Power
Normally the average power is the power of interest in AC circuits. Since the
expression for the instantaneous power
Pinstanteneous = Vm Im sin 2ωt cosφ - Vm Im sinωt sinφ cos ωt
is a continuously varying one with time, the average must be obtained by integration.
Averaging over one period T of the sinusoidal function will give the average power.
The second term in the power expression above averages to zero since it is an odd
function of t.
