DEKI CAPACITOR SOLUTIONS

By

Vishnu –Engineer R&D

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

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CAPACITOR…

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CAPACITOR…

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CONSTRUCTION

SYMBOL

ELECTRODE

DIELECTRIC

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=CV2/2

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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)

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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)

Dissipation Factor…

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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 / ϖCThe 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 × U2

where f = frequency, tan δ = maximum value specified,

U =rated voltage

ESR & Power dissipation…

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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

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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

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DEKI Film CAPACITORS…

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INDUCTIVE (MYLAR)

FRONT VIEWSIDE VIEW

Al.FOIL

L.O.FILM

PLAIN .FILM

High Dv/dt

High IR

Good Current carrying capability.

Better capacitance stability

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D104K1J

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NON-INDUCTIVE

METALLISED FILM 1

METALLISED FILM 2

METALLISED FILM 1

METALLISED FILM 2

METALLISED FILM 1

METALLISED FILM 2

For voltage 250 VAC For voltage 500 VAC

For voltage 750 VAC

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Smaller size.

High Reliability

Self Healing

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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 non-metallized unit.

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If the maximum operating temperature

<=105oC - PP film

<=120oC - PET film

<=150oC - PEN film

>150oC - PPS film (upto to 170oC)

For PP film,

• Tanδ<0.0008 at 1 kHz,

• Tanδ<0.001 at 10 kHz,

• Tanδ<0.003 at 100 kHz.

In cost, PPS>PEN>PP>PET film

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Selection of films

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For PET film,• Tanδ<0.008 at 1 kHz,• Tanδ<0.015 at 10 kHz,• Tanδ<0.030 at 100 kHz.

Properties of Films

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For PET film:

For PP film:

Dielectric constant Vs Temperature

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C = εoεrA/D

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Properties of Films

For PP film:

For PET film:

Tanδ Vs Temperature

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ESR = tan δ / 2 fC

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Properties of Films Insulation resistance Vs Temperature

For PET film:

For PP film:

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Comparison of films

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DC Application

Vr > DC voltage of the signal

IR should be very high

AC Application

tanδ is very important

self-heating

Pulse Application

high current/voltage pulses at short durations

self-heating

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Selection by application

WHY POLYPROPYLENE CAPACITOR FOR SWITCHING

Polypropylene capacitor is ideal choice for high frequency applicationsbecause of its low loss factor. For striking, the capacitor should havehigh dv/dt rating and low loss factor. Low loss factor is preferredbecause

P = 2. . f.C.tan δ .VRMS2 --------(1)

∆T = P . RTH C --------(2)

P = power dissipation in capacitor. ∆T = Temperature Rise

RTH = Thermal resistance of the capacitor

From above eq. we can tell power dissipation is directly proportional tothe frequency, loss factor and VRMS .Heat generated in the capacitor is

proportional to the power dissipation. But temperature rise is notallowed more than 10 C at its category temperature. For polypropylenecapacitors loss factor is low at high frequency .so the temperature riseconsiderable less than other capacitor.

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CFL…

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RFI SUPPRESSION-(C1)Cap Value : 68nf to 220nfX2-Series –275 VACMPET –( 400 –630 Vdc)

START UP-(C2)Cap Value :10nf to 100nf(63 –100Vdc) PET Film foil inductive typeMPET For C > 0.082 Mfd

CFL…( RFI Suppression and Startup)

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CFL…( Snubber & Blocking)

SNUBBER-(C3)0.68nf to 0.0033μf(630-1000Vdc)PP Film foil inductive PEP film foil inductive

BLOCKING-(C4)Recommended Capacitor is PET ( Film/Foil) .MPET ( Box &Dip) Cap Value : 0.022 –0.068μfRated Voltage : 250 –400Vdc

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STRIKING-( C5)cap 0.0022μF to 0.0068 μf.

PP inductive typePET inductive type PEP film foil inductiveDPSHMPP-MPP

CFL…( Striking)

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H.F Ballast…

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)

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.

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RFI Filter

P.F.C

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H.F Ballast… (Striking)

Deki Range …AC & Pulse capacitor seriesa) MPP/MPP AC-seriesb) PP/MPP seriesc) MMPP series

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V

VP

DURING STARING

VP-P

NORMAL OPERATION

Selection of capacitor for striking

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.

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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.

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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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