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[2]
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.
[3]
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)
[5]
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.
[6]
Power Factor
• Ratio of the actual power transmitted to the apparent power transmitted.
Power Factor = Apparent power/reactive power
• Power Triangle
[7]
Improvement of Power Factor• Save money on utility bills
• Increase internal electrical system capacity
• Improve voltage drop at point of use
[8]
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
[9]
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
[10]
• Capacitor change vs. A.C volts • Capacitor change vs. D.C volts
• Capacitor change vs. Temperature • Capacitor change vs. Frequency
[11]
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
[12]
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
[13]
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.