CV Capability Guide - AVX

High Voltage Ceramic CapacitorsType HP/HWType HD/HESELECTION GUIDEMain Signal Application Series Type Size FinishComponentPulses High Energy Molded discs HP 30 EpoxyAC or DC Pulses with 40 pottedor AC connections 50or DC 60Uncoated HW 30 Uncoateddiscs with 40connections 5060AC AC Voltage Molded discs HD 30 Epoxydividers at with 40 pottedline frequency connectors 60Uncoated HE 30 Uncoateddiscs with 40connectors 60GENERAL CHARACTERISTICSHIGH VOLTAGE / AC USES• The main applications include live line indicators, AC dividers,grading systems for power distribution network, protection forHV switches and power circuit breakers. Coupling, by-passinghigh frequency circuits also use HV ceramic disc capacitors.• These applications require:- a high internal resistance.- a high dielectric strength.- low or moderate losses at working frequencies (from 50Hz up to 10 kHz).The active power (or losses) being:Wa = 2ΠFC tg δ V 2 = k (Ctg δ) (FV 2 )This shows that improved performances are obtainedwhen:- Good dielectric properties (low tg δ) and- No long term overvoltage are present and- Capacitors free of “partial discharge” (corona) effect,up to rated rms voltage.TPC is able to perform “discharge free test” and mayguarantee a rate as low as 5 picocoulombs at V rms uponrequest.• High voltage capacitors for AC uses are mainly made of typeII dielectrics. Most of these materials except strontium titanateexhibit a significant non-linearity. Consequently, the capacitancevalue depends on the voltage across the componentand on the frequency of the applied signal.Check for up-to-date CV Tables athttp://www.avx.com/docs/catalogs/hp-hw-hk.pdfHIGH ENERGY PULSES• Laser pulses circuitry, high energy/high voltage test equipment(HV accelerators, physics research) require productsespecially adapted to their specific requirements.• Because of the high energy involved, the design of the capacitorshave to provide:- a very low ESR (equivalent series resistance) to mini-mizethe lossed energy.W = ∫ ip (ESR 2 ) di- a very low ESL (equivalent series inductance) to keep thecorrect pulse shape.Typically due to the design of the electrodes, the productsexhibit:- ESR: ~ 10 mΩ- ESL: < 30 nH- peak current up to 50 kA- a high withstanding of very large dV or short signal risetime.- a high energy density JJ = 1 2k ε o ε r E 2 (with E = V/m)even under high electric field, (implying that ε r is very littlevoltage dependent).Through the use of almost linear or non-voltage dependentcapacitors, the stored energy can reach 50 to 100J/liter for the HP/HW products.• To ensure these properties, traditional ferroelectric type IIcapacitors cannot be used due to their electrostrictive andpiezoelectric properties. The capacitors use quasi “paraelectric”,strontium-based, ceramic material.• The main applications are coupling, decoupling, multiplierscircuits, HV DC power supplies, high voltage dividers.dt144 | www.avx.com