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POWER CAPACITOR AND REACTIVE

POWER MANAGEMENT

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INTRODUCTION

• Capacitor is a relatively unknown device until recently in our power systems.

• The capacitor found no use when the power systems are simple and very small.

• Capacitor needed to determine the optimum power factor correction and in our electrical distribution system.

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Working of Capacitor

• Capacitor

• Formula for Determining Capacitance is:

C = (.224 KA)/t

C = capacitance (Pico farads)

K = dielectric constant (Vacuum = 1)

A = area in square inches

t = separation between the plates in inches (thickness of dielectric)

.224 = conversion constant (.0884 for metric system in cm)

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Basic Capacitor Formulas

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Types of Capacitors• Metalised Polypropylene Capacitors These capacitors

are mostly suitably for lower voltage i.e 400V and motor load only.

• Mixed Dielectric Capacitors These are used for HT system.

• All Polypropylene Capacitors These are used for HT system. But performances are usually better than mixed

dielectric variety.

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Power Factor

• Ratio of the actual power transmitted to the apparent power transmitted.

Power Factor = Apparent power/reactive power

• Power Triangle

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Improvement of Power Factor• Save money on utility bills

• Increase internal electrical system capacity

• Improve voltage drop at point of use

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Correction of Power Factor• Capacitors draw leading

reactive power.

• Replace over-sized motors with efficiency motors of the right horsepower.

• Avoid operation of equipment above its rated voltage

• Effect of Power Factor Correction

• Capacitive Reactance/Inductive Reactance

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CERAMIC CAPACITORS • Manufactured by mixing the

ceramic powder in an organic binder (slurry) and casting it by one technique or another into thin layers typically ranging from about 3 mils in thickness down to 1 mil or thinner.

• Metal electrodes are deposited onto the green ceramic layers which are then stacked to form a laminated structure.

• On sintering at high temperature the part becomes a monolithic block which can provide extremely high capacitance values in small mechanical volumes. • Ceramic capacitors

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• Capacitor change vs. A.C volts • Capacitor change vs. D.C volts

• Capacitor change vs. Temperature • Capacitor change vs. Frequency

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SNUBBER/POWER CAPACITORS (Polypropylene) • High current "power

capacitors“.• High reliability and

condensed size.• Low inductance and power

consumption.• High peak/RMS currents

and good frequency response.

• Applications :- IGBT, SMPS, TV Deflections, AC Voltage Applications, Motor Controls • Snubber/Power Capacitor

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COOPER POWER SYSTEMS TYPE EX®-D. 125% continuous RMS

over volt age capability.• 135% peak over voltage

capability• greater safety through

improved tank rupture characteristics

• Iow dielectric losses (0.07 watts/kVAR @ 60 Hz)

• superior electrical performance and reliability

• n environmentally acceptable

EX®-D single-phase, all-film

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CONCLUSION • Capacitor suppliers and engineering firms can

provide the assistance may need to determine the optimum power factor correction and to correctly locate and install capacitors in our electrical distribution system.

• Capacitor enhances increase internal electrical system capacity, save money on utility bills and improve voltage drop at point of use.

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