DEKI CAPACITOR SOLUTIONS By Vishnu Engineer R&D
CAPACITOR A capacitor is a passive electronic component. It forms the basic building block of an electronic circuit. Without capacitor electronic circuits cannot be designed It is a device for storing electric charge. consisting of a pair of conductors separated by a dielectric. for blocking direct current while allowing alternating current to pass C = Q/V Farads 2
CAPACITOR ELECTRODE DIELECTRIC SYMBOL CONSTRUCTION 3
Theory of Operation When the supply is given to the conducting plates. The dielectric between the conducting plates will polarize and arrange themselves in a regular fashion. An electron flow occurs from negatively charged plate to the positively charged plate due to polarization Thus current flow from positively charged plate to the negative plate The energy stored in the capacitor is given by E=CV 2 /2 4
Parameters A capacitor has four important parameters. Rated Capacitance Rated Voltage Insulation Resistance It is the measure of resistivity in dc. Under a stationary dc voltage, a leakage current flows through the dielectric and over the capacitance surfaces. Rins =V (applied voltage)/i (Leakage current) Loss Factor or dissipation Factor(Tanδ) 5
Dissipation Factor With a perfect dielectric capacitor, current will lead the applied voltage by 90º. When dealing with less than perfect dielectric materials, current in a capacitor will lead the applied voltage by less than 90. This can be visualized in the current-voltage phase relation of a dielectric visualized in The loss angle is usually expressed as the tangent of delta, or just tan delta(dissipation factor) 6
ESR & Power dissipation The ESR is the resistive part of the equivalent series circuit and is temperature and frequency dependent. The ESR can be calculated from the dissipation factor (tan δ) as follows: ESR = tan δ / ϖc The power dissipated by a capacitor is a function of the voltage across or the current (I) through the equivalent series resistance ESR. P = w C tan δ U2 P = 2 π f C tan δ U 2 where f = frequency, tan δ = maximum value specified, U =rated voltage 7
Types of capacitors Depending upon the dielectric used, there are several types of capacitors Ceramic Capacitors Paper capacitors Glass capacitors Electrolytic capacitors Film capacitors Polyester film dielectric Polypropylene film dielectric Polyethylene Naphthalate dielectric Polyphenylene sulphide dielectric
DEKI Film CAPACITORS INDUCTIVE (MYLAR) NON-INDUCTIVE 1 ) PP (POLYPROPYLENE) 2) PET (POLYESTER) 3) PEP (POLYPROPYLENE + POLYESTER) 4) PES 5) PSH 1 )MPP 2) MPET 3) PP-NI,PET-NI 4) PP-MPP 9
INDUCTIVE (MYLAR) High Dv/dt High IR SIDE VIEW PLAIN.FILM FRONT VIEW Good Current carrying capability. Al.FOIL L.O.FILM Better capacitance stability D 104 K1J 10
NON-INDUCTIVE METALLISED FILM 1 METALLISED FILM 1 METALLISED FILM 2 METALLISED FILM 2 For voltage 250 VAC For voltage 500 VAC METALLISED FILM 1 METALLISED FILM 2 Smaller size. High Reliability Self Healing For voltage 750 VAC 11
Self Healing For capacitors made with metalized film, self-healing or "clearing" removes a fault or short circuit in the dielectric film by vaporizing the metallization near the defect The vaporized metal oxidizes over time, aiding in the isolation of a fault area. The self-healing feature of the metallized capacitor offers a distinct advantage over the nonmetallized unit. 12
Selection of films If the maximum operating temperature <=105 o C - PP film <=120 o C - PET film <=150 o C - PEN film >150 o C - PPS film (upto to 170 o C) For PP film, Tanδ<0.0008 at 1 khz, Tanδ<0.001 at 10 khz, Tanδ<0.003 at 100 khz. For PET film, Tanδ<0.008 at 1 khz, Tanδ<0.015 at 10 khz, Tanδ<0.030 at 100 khz. In cost, PPS>PEN>PP>PET film 13
Properties of Films Dielectric constant Vs Temperature For PET film: C = ε o ε r A/D For PP film: 14
Properties of Films Tanδ Vs Temperature ESR = tan δ / 2 fc For PET film: For PP film: 15
Properties of Films Insulation resistance Vs Temperature For PET film: For PP film: 16
Comparison of films 17
Selection by application DC Application AC Application Pulse Application Vr > DC voltage of the signal IR should be very high tanδ is very important self-heating high current/voltage pulses at short durations self-heating 18
WHY POLYPROPYLENE CAPACITOR FOR SWITCHING Polypropylene capacitor is ideal choice for high frequency applications because of its low loss factor. For striking, the capacitor should have high dv/dt rating and low loss factor. Low loss factor is preferred because P = 2.. f.c.tan δ.v RMS 2 --------(1) T = P. R TH C --------(2) P = power dissipation in capacitor. T = Temperature Rise R TH = Thermal resistance of the capacitor From above eq. we can tell power dissipation is directly proportional to the frequency, loss factor and V RMS.Heat generated in the capacitor is proportional to the power dissipation. But temperature rise is not allowed more than 10 C at its category temperature. For polypropylene capacitors loss factor is low at high frequency.so the temperature rise considerable less than other capacitor. 19
CFL 20
CFL ( RFI Suppression and Startup) RFI SUPPRESSION-(C1) Cap Value : 68nf to 220nf X2-Series 275 VAC MPET ( 400 630 Vdc) START UP-(C2) Cap Value :10nf to 100nf(63 100Vdc) PET Film foil inductive type MPET For C > 0.082 Mfd 21
CFL ( Snubber & Blocking) BLOCKING-(C4) Recommended Capacitor is PET ( Film/Foil). MPET ( Box &Dip) Cap Value : 0.022 0.068μf Rated Voltage : 250 400Vdc SNUBBER-(C3) 0.68nf to 0.0033μf(630-1000Vdc) PP Film foil inductive PEP film foil inductive 22
CFL ( Striking) STRIKING-( C5) cap 0.0022μF to 0.0068 μf. PP inductive type PET inductive type PEP film foil inductive DPSH MPP-MPP 23
H.F Ballast P.F.C For smoothening the wave form after PFC correction Deki has MPET as well as MPP series.range starts from 10 nf to 10 Mfd. Voltage range is from 420 VDC to 630 VDC. RFI Filter Capacitance value(rfi Filter) : 0.0047 Mfd to 2.2 Mfd (for C1-X2 Class (275VAC/305Vac) 0.001Mfd to 0.1 Mfd (for C2,C3-250 ~275VAC) 24
H.F Ballast (Striking) Deki Range AC & Pulse capacitor series a) MPP/MPP AC-series b) PP/MPP series c) MMPP series 25
Selection of capacitor for striking V DURING STARING NORMAL OPERATION V P V P-P Following condition should be satisfied when selecting capacitor for striking application. VP Should be less than D.C Rated voltage. VP-P should be less than 2x1.414x VRMS. dv/dt rating should be fulfilled Peak current should be less than C(dv/dt) Temperature rise should be less than 10 C at its category temperature. 26
Capacitors for Energy meters A capacitive power supply is the best solution for a low-cost energy meter. It works on the principle of reducing the line voltage (Voltage dropper) by having a series capacitor between phase and neutral. Current flowing through this capacitor is inversely proportional to the impedance of the capacitor as given by the formula: Impedance (Z) = 1/(2πfC) f is the line frequency and C is the capacitance of the series impedance capacitor.
Capacitance Function Type Voltage Range Capacitance range C1 Noise filter MPP-X2 275Vac/305Vac 0.01 to 1μF C2 Ripple filter Electrolytic - - C3 (Series impeda nce capacit or) Voltage Dropper MPP-AC, MPP- X2, MPET- AC-High capacitance stability 275Vac/305Vac, 325Vac, 440Vac 0.1 to 1μF
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