DOCSLIB.ORG

2. Capacitors Contents

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
2. Capacitors Contents 2. Capacitors Contents 1 Capacitor 1 1.1 History ................................................. 2 1.2 Theory of operation .......................................... 2 1.2.1 Overview ........................................... 3 1.2.2 Hydraulic analogy ....................................... 3 1.2.3 Energy of electric field .................................... 4 1.2.4 Current–voltage relation ................................... 4 1.2.5 DC circuits .......................................... 4 1.2.6 AC circuits .......................................... 5 1.2.7 Laplace circuit analysis (s-domain) .............................. 5 1.2.8 Parallel-plate model ...................................... 5 1.2.9 Networks ........................................... 6 1.3 Non-ideal behavior .......................................... 7 1.3.1 Breakdown voltage ...................................... 7 1.3.2 Equivalent circuit ....................................... 7 1.3.3 Q factor ............................................ 8 1.3.4 Ripple current ......................................... 8 1.3.5 Capacitance instability .................................... 8 1.3.6 Current and voltage reversal ................................. 9 1.3.7 Dielectric absorption ..................................... 9 1.3.8 Leakage ............................................ 9 1.3.9 Electrolytic failure from disuse ................................ 9 1.4 Capacitor types ............................................ 9 1.4.1 Dielectric materials ...................................... 10 1.4.2 Structure ........................................... 11 1.5 Capacitor markings .......................................... 11 1.5.1 Example ............................................ 12 1.6 Applications .............................................. 12 1.6.1 Energy storage ........................................ 12 1.6.2 Pulsed power and weapons .................................. 12 1.6.3 Power conditioning ...................................... 12 1.6.4 Suppression and coupling ................................... 13 i ii CONTENTS 1.6.5 Motor starters ......................................... 14 1.6.6 Signal processing ....................................... 14 1.6.7 Sensing ............................................ 14 1.6.8 Oscillators ........................................... 15 1.7 Hazards and safety ........................................... 15 1.8 See also ................................................ 15 1.9 References ............................................... 16 1.10 Bibliography .............................................. 16 1.11 External links ............................................. 17 2 Types of capacitor 18 2.1 General remarks ........................................... 18 2.1.1 Theory of conventional construction ............................. 18 2.1.2 Theory of electrochemical construction ........................... 19 2.1.3 Common capacitors and their names ............................. 19 2.1.4 Dielectrics .......................................... 20 2.1.5 Capacitance and voltage range ................................ 21 2.1.6 Miniaturization ........................................ 21 2.1.7 Overlapping range of applications .............................. 21 2.2 Types and styles ............................................ 21 2.2.1 Ceramic capacitors ...................................... 22 2.2.2 Film capacitors ........................................ 22 2.2.3 Film power capacitors .................................... 23 2.2.4 Electrolytic capacitors .................................... 24 2.2.5 Supercapacitors ........................................ 25 2.2.6 Class X and Class Y capacitors ................................ 26 2.2.7 Miscellaneous capacitors ................................... 26 2.2.8 Variable capacitors ...................................... 27 2.3 Comparison of types ......................................... 27 2.4 Electrical characteristics ....................................... 27 2.4.1 Series-equivalent circuit ................................... 27 2.4.2 Standard capacitance values and tolerances ......................... 28 2.4.3 Temperature dependence ................................... 28 2.4.4 Frequency dependence .................................... 28 2.4.5 Voltage dependence ..................................... 28 2.4.6 Rated and category voltage .................................. 29 2.4.7 Impedance .......................................... 29 2.4.8 Inductance (ESL) and self-resonant frequency ........................ 30 2.4.9 Ohmic losses, ESR, dissipation factor, and quality factor .................. 31 2.4.10 Limiting current loads .................................... 31 2.4.11 Insulation resistance and self-discharge constant ....................... 33 2.4.12 Leakage current ....................................... 34 CONTENTS iii 2.4.13 Microphonics ......................................... 34 2.4.14 Dielectric absorption (soakage) ................................ 35 2.4.15 Energy density ........................................ 35 2.4.16 Long time behavior, aging .................................. 35 2.4.17 Failure rate .......................................... 36 2.5 Additional information ........................................ 37 2.5.1 Soldering ........................................... 37 2.5.2 Electrolytic behavior from storage or disuse ......................... 37 2.5.3 IEC/EN standards ...................................... 37 2.5.4 Capacitor symbols ...................................... 38 2.5.5 Markings ........................................... 38 2.5.6 Polarity marking ....................................... 39 2.6 Market segments ........................................... 39 2.7 See also ................................................ 39 2.8 References .............................................. 39 2.9 External links ............................................. 41 3 Farad 42 3.1 Definition ............................................... 42 3.1.1 Equalities ........................................... 42 3.2 History ................................................ 42 3.3 Explanation .............................................. 42 3.3.1 Informal terminology ..................................... 43 3.3.2 Related concepts ....................................... 43 3.4 CGS units ............................................... 43 3.5 See also ................................................ 43 3.6 Notes ................................................. 43 3.7 External links ............................................. 43 3.8 Text and image sources, contributors, and licenses .......................... 44 3.8.1 Text .............................................. 44 3.8.2 Images ............................................ 45 3.8.3 Content license ........................................ 47 Chapter 1 Capacitor This article is about the electronic component. For the physical phenomenon, see capacitance. For an overview of various kinds of capacitors, see types of capacitor. “Capacitive” redirects here. For the term used when re- ferring to touchscreens, see capacitive sensing. A capacitor (originally known as a condenser) is a 4 electrolytic capacitors of different voltages and capacitance Miniature low-voltage capacitors (next to a cm ruler) Solid electrolyte, resin-dipped 10 μF 35 V tantalum capacitors. The + sign indicates the positive lead. or sintered beads of metal or conductive electrolyte, etc. The nonconducting dielectric acts to increase the capaci- tor’s charge capacity. A dielectric can be glass, ceramic, plastic film, air, vacuum, paper, mica, oxide layer etc. Capacitors are widely used as parts of electrical circuits A typical electrolytic capacitor in many common electrical devices. Unlike a resistor, an passive two-terminal electrical component used to store ideal capacitor does not dissipate energy. Instead, a ca- energy electrostatically in an electric field. The forms of pacitor stores energy in the form of an electrostatic field practical capacitors vary widely, but all contain at least between its plates. two electrical conductors (plates) separated by a dielectric When there is a potential difference across the conductors (i.e. insulator). The conductors can be thin films, foils (e.g., when a capacitor is attached across a battery), an 1 2 CHAPTER 1. CAPACITOR electric field develops across the dielectric, causing posi- tive charge +Q to collect on one plate and negative charge −Q to collect on the other plate. If a battery has been attached to a capacitor for a sufficient amount of time, no current can flow through the capacitor. However, if a time-varying voltage is applied across the leads of the capacitor, a displacement current can flow. An ideal capacitor is characterized by a single constant value for its capacitance. Capacitance is expressed as the ratio of the electric charge Q on each conductor to the potential difference V between them. The SI unit of ca- pacitance is the farad (F), which is equal to one coulomb per volt (1 C/V). Typical capacitance values range from about 1 pF (10−12 F) to about 1 mF (10−3 F). The capacitance is greater when there is a narrower sepa- ration between conductors and when the conductors have a larger surface area. In practice, the dielectric between the plates passes a small amount of leakage current and also has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired
Load more

Recommended publications
  • Run Capacitor Info-98582
    Run Cap Quiz-98582_Layout 1 4/16/15 10:26 AM Page 1 ® Run Capacitor Info WHAT IS A CAPACITOR? Very simply, a capacitor is a device that stores and discharges electrons. While you may hear capacitors referred to by a variety of names (condenser, run, start, oil, etc.) all capacitors are comprised of two or more metallic plates separated by an insulating material called a dielectric. PLATE 1 PLATE 2 A very simple capacitor can be made with two plates separated by a dielectric, in this PLATE 1 PLATE 2 case air, and connected to a source of DC current, a battery. Electrons will flow away from plate 1 and collect on plate 2, leaving it with an abundance of electrons, or a “charge”. Since current from a battery only flows one way, the capacitor plate will stay BATTERY + – charged this way unless something causes current flow. If we were to short across the plates with a screwdriver, the resulting spark would indicate the electrons “jumping” from plate 2 to plate 1 in an attempt to equalize. As soon as the screwdriver is removed, plate 2 will again collect a PLATE 1 PLATE 2 charge. + BATTERY – Now let’s connect our simple capacitor to a source of AC current and in series with the windings of an electric motor. Since AC current alternates, first one PLATE 1 PLATE 2 MOTOR plate, then the other would be charged and discharged in turn. First plate 1 is charged, then as the current reverses, a rush of electrons flow from plate 1 to plate 2 through the motor windings.
    [Show full text]
  • Switched-Capacitor Circuits
    Switched-Capacitor Circuits David Johns and Ken Martin University of Toronto ([email protected]) ([email protected]) University of Toronto 1 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Opamps • Ideal opamps usually assumed. • Important non-idealities — dc gain: sets the accuracy of charge transfer, hence, transfer-function accuracy. — unity-gain freq, phase margin & slew-rate: sets the max clocking frequency. A general rule is that unity-gain freq should be 5 times (or more) higher than the clock-freq. — dc offset: Can create dc offset at output. Circuit techniques to combat this which also reduce 1/f noise. University of Toronto 2 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Double-Poly Capacitors metal C1 metal poly1 Cp1 thin oxide bottom plate C1 poly2 Cp2 thick oxide C p1 Cp2 (substrate - ac ground) cross-section view equivalent circuit • Substantial parasitics with large bottom plate capacitance (20 percent of C1) • Also, metal-metal capacitors are used but have even larger parasitic capacitances. University of Toronto 3 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Switches I I Symbol n-channel v1 v2 v1 v2 I transmission I I gate v1 v p-channel v 2 1 v2 I • Mosfet switches are good switches. — off-resistance near G: range — on-resistance in 100: to 5k: range (depends on transistor sizing) • However, have non-linear parasitic capacitances. University of Toronto 4 of 60 © D. Johns, K. Martin, 1997 Basic Building Blocks Non-Overlapping Clocks I1 T Von I I1 Voff n – 2 n – 1 n n + 1 tTe delay 1 I fs { --- delay V 2 T on I Voff 2 n – 32e n – 12e n + 12e tTe • Non-overlapping clocks — both clocks are never on at same time • Needed to ensure charge is not inadvertently lost.
    [Show full text]
  • Kirchhoff's Laws in Dynamic Circuits
    Kirchhoff’s Laws in Dynamic Circuits Dynamic circuits are circuits that contain capacitors and inductors. Later we will learn to analyze some dynamic circuits by writing and solving differential equations. In these notes, we consider some simpler examples that can be solved using only Kirchhoff’s laws and the element equations of the capacitor and the inductor. Example 1: Consider this circuit Additionally, we are given the following representations of the voltage source voltage and one of the resistor voltages: ⎧⎧10 V fortt<< 0 2 V for 0 vvs ==⎨⎨and 1 −5t ⎩⎩20 V forte>+ 0 8 4 V fort> 0 We wish to express the capacitor current, i 2 , as a function of time, t. Plan: First, apply Kirchhoff’s voltage law (KVL) to the loop consisting of the source, resistor R1 and the capacitor to determine the capacitor voltage, v 2 , as a function of time, t. Next, use the element equation of the capacitor to determine the capacitor current as a function of time, t. Solution: Apply Kirchhoff’s voltage law (KVL) to the loop consisting of the source, resistor R1 and the capacitor to write ⎧ 8 V fort < 0 vvv12+−=ss0 ⇒ v2 =−= vv 1⎨ −5t ⎩16− 8et V for> 0 Use the element equation of the capacitor to write ⎧ 0 A fort < 0 dv22 dv ⎪ ⎧ 0 A fort < 0 iC2 ==0.025 =⎨⎨d −5t =−5t dt dt ⎪0.025() 16−> 8et for 0 ⎩1et A for> 0 ⎩ dt 1 Example 2: Consider this circuit where the resistor currents are given by ⎧⎧0.8 A fortt<< 0 0 A for 0 ii13==⎨⎨−−22ttand ⎩⎩0.8et−> 0.8 A for 0 −0.8 e A fort> 0 Express the inductor voltage, v 2 , as a function of time, t.
    [Show full text]
  • Capacitive Voltage Transformers: Transient Overreach Concerns and Solutions for Distance Relaying
    Capacitive Voltage Transformers: Transient Overreach Concerns and Solutions for Distance Relaying Daqing Hou and Jeff Roberts Schweitzer Engineering Laboratories, Inc. Revised edition released October 2010 Previously presented at the 1996 Canadian Conference on Electrical and Computer Engineering, May 1996, 50th Annual Georgia Tech Protective Relaying Conference, May 1996, and 49th Annual Conference for Protective Relay Engineers, April 1996 Previous revised edition released July 2000 Originally presented at the 22nd Annual Western Protective Relay Conference, October 1995 CAPACITIVE VOLTAGE TRANSFORMERS: TRANSIENT OVERREACH CONCERNS AND SOLUTIONS FOR DISTANCE RELAYING Daqing Hou and Jeff Roberts Schweitzer Engineering Laboratories, Inc. Pullman, W A USA ABSTRACT Capacitive Voltage Transformers (CVTs) are common in high-voltage transmission line applications. These same applications require fast, yet secure protection. However, as the requirement for faster protective relays grows, so does the concern over the poor transient response of some CVTs for certain system conditions. Solid-state and microprocessor relays can respond to a CVT transient due to their high operating speed and iflCreased sensitivity .This paper discusses CVT models whose purpose is to identify which major CVT components contribute to the CVT transient. Some surprises include a recom- mendation for CVT burden and the type offerroresonant-suppression circuit that gives the least CVT transient. This paper also reviews how the System Impedance Ratio (SIR) affects the CVT transient response. The higher the SIR, the worse the CVT transient for a given CVT . Finally, this paper discusses improvements in relaying logic. The new method of detecting CVT transients is more precise than past detection methods and does not penalize distance protection speed for close-in faults.
    [Show full text]
  • Introduction What Is a Polymer Capacitor?
    ECAS series (polymer-type aluminum electrolytic capacitor) No. C2T2CPS-063 Introduction If you take a look at the main board of an electronic device such as a personal computer, you’re likely to see some of the six types of capacitors shown below (Fig. 1). Common types of capacitors include tantalum electrolytic capacitors (MnO2 type and polymer type), aluminum electrolytic capacitors (electrolyte can type, polymer can type, and chip type), and MLCC. Figure 1. Main Types of Capacitors What Is a Polymer Capacitor? There are many other types of capacitors, such as film capacitors and niobium capacitors, but here we will describe polymer capacitors, a type of capacitor produced by Murata among others. In both tantalum electrolytic capacitors and aluminum electrolytic capacitors, a polymer capacitor is a type of electrolytic capacitor in which a conductive polymer is used as the cathode. In a polymer-type aluminum electrolytic capacitor, the anode is made of aluminum foil and the cathode is made of a conductive polymer. In a polymer-type tantalum electrolytic capacitor, the anode is made of the metal tantalum and the cathode is made of a conductive polymer. Figure 2 shows an example of this structure. Figure 2. Example of Structure of Conductive Polymer Aluminum Capacitor In conventional electrolytic capacitors, an electrolyte (electrolytic solution) or manganese dioxide (MnO2) was used as the cathode. Using a conductive polymer instead provides many advantages, making it possible to achieve a lower equivalent series resistance (ESR), more stable thermal characteristics, improved safety, and longer service life. As can be seen in Fig. 1, polymer capacitors have lower ESR than conventional electrolytic Copyright © muRata Manufacturing Co., Ltd.
    [Show full text]
  • Capacitors and Inductors
    DC Principles Study Unit Capacitors and Inductors By Robert Cecci In this text, you’ll learn about how capacitors and inductors operate in DC circuits. As an industrial electrician or elec- tronics technician, you’ll be likely to encounter capacitors and inductors in your everyday work. Capacitors and induc- tors are used in many types of industrial power supplies, Preview Preview motor drive systems, and on most industrial electronics printed circuit boards. When you complete this study unit, you’ll be able to • Explain how a capacitor holds a charge • Describe common types of capacitors • Identify capacitor ratings • Calculate the total capacitance of a circuit containing capacitors connected in series or in parallel • Calculate the time constant of a resistance-capacitance (RC) circuit • Explain how inductors are constructed and describe their rating system • Describe how an inductor can regulate the flow of cur- rent in a DC circuit • Calculate the total inductance of a circuit containing inductors connected in series or parallel • Calculate the time constant of a resistance-inductance (RL) circuit Electronics Workbench is a registered trademark, property of Interactive Image Technologies Ltd. and used with permission. You’ll see the symbol shown above at several locations throughout this study unit. This symbol is the logo of Electronics Workbench, a computer-simulated electronics laboratory. The appearance of this symbol in the text mar- gin signals that there’s an Electronics Workbench lab experiment associated with that section of the text. If your program includes Elec tronics Workbench as a part of your iii learning experience, you’ll receive an experiment lab book that describes your Electronics Workbench assignments.
    [Show full text]
  • Aluminum Electrolytic Vs. Polymer – Two Technologies – Various Opportunities
    Aluminum Electrolytic vs. Polymer – Two Technologies – Various Opportunities By Pierre Lohrber BU Manager Capacitors Wurth Electronics @APEC 2017 2017 WE eiCap @ APEC PSMA 1 Agenda Electrical Parameter Technology Comparison Application 2017 WE eiCap @ APEC PSMA 2 ESR – How to Calculate? ESR – Equivalent Series Resistance ESR causes heat generation within the capacitor when AC ripple is applied to the capacitor Maximum ESR is normally specified @ 120Hz or 100kHz, @20°C ESR can be calculated like below: ͕ͨ͢ 1 1 ͍̿͌ Ɣ Ɣ ͕ͨ͢ ∗ ͒ ͒ Ɣ Ɣ 2 ∗ ∗ ͚ ∗ ̽ 2 ∗ ∗ ͚ ∗ ̽ ! ∗ ̽ 2017 WE eiCap @ APEC PSMA 3 ESR – Temperature Characteristics Electrolytic Polymer Ta Polymer Al Ceramics 2017 WE eiCap @ APEC PSMA 4 Electrolytic Conductivity Aluminum Electrolytic – Caused by the liquid electrolyte the conductance response is deeply affected – Rated up to 0.04 S/cm Aluminum Polymer – Solid Polymer pushes the conductance response to much higher limits – Rated up to 4 S/cm 2017 WE eiCap @ APEC PSMA 5 Electrical Values – Who’s Best in Class? Aluminum Electrolytic ESR approx. 85m Ω Tantalum Polymer Ripple Current rating approx. ESR approx. 200m Ω 630mA Ripple Current rating approx. 1,900mA Aluminum Polymer ESR approx. 11m Ω Ripple Current rating approx. 5,500mA 2017 WE eiCap @ APEC PSMA 6 Ripple Current >> Temperature Rise Ripple current is the AC component of an applied source (SMPS) Ripple current causes heat inside the capacitor due to the dielectric losses Caused by the changing field strength and the current flow through the capacitor 2017 WE eiCap @ APEC PSMA 7 Impedance Z ͦ 1 ͔ Ɣ ͍̿͌ ͦ + (͒ −͒ )ͦ Ɣ ͍̿͌ ͦ + 2 ∗ ∗ ͚ ∗ ͍̿͆ − 2 ∗ ∗ ͚ ∗ ̽ 2017 WE eiCap @ APEC PSMA 8 Impedance Z Impedance over frequency added with ESR ratio 2017 WE eiCap @ APEC PSMA 9 Impedance @ High Frequencies Aluminum Polymer Capacitors have excellent high frequency characteristics ESR value is ultra low compared to Electrolytic’s and Tantalum’s within 100KHz~1MHz E.g.
    [Show full text]
  • Microphonics & Lorentz Detuning: Determined by Cavity/Cryomodule Design and Background Environment
    Old Dominion University October 2012 2 2 2 f opt (b 1) fo IRQQ(/) where b oocos V Phase Amplitude Controller Controller Klystron 1.0 Limiter 0.9 0.8 Loop 0.7 Phase Amplitude 0.6 CEBAF 6 GeV Set Point 0.5 Amplitude CEBAF Upgrade Detector 0.4 Cavity 0.3 0.2 Energy Content (Normalized)Content Energy 0.1 Reference Phase 0.0 Phase -1,000 -800 -600 -400 -200 0 200 Set Point Detector Detuning (Hz) • RF Systems • What are you controlling? • Cavity Equations • Control Systems Cavity Models • Algorithms Generator Driven Resonator (GDR) Self Excited Loop (SEL) • Hardware Receiver ADC/Jitter Transmitter Digital Signal Processing • Cavity Tuning & Resonance Control Stepper Motor Piezo • RF Systems are broken RF Control Power down into two parts. Electronics Amplifier • The high power section consisting of the power amplifier and the high power transmission line Waveguide/ (waveguide or coax) Coax • The Low power (level) section (LLRF) consisting of the field and resonance control components Cavity • Think your grandfathers “Hi-Fi” stereo or your guitar amp. • Intensity modulation of DC beam by control grid • Efficiency ~ 50-70% (dependent on operation Triode Tetrode mode) • Gain 10-20 dB • Frequency dc – 500 MHz • Power to 1 MW • Velocity modulation with input Cavity • Drift space and several cavities to achieve bunching • It is highly efficient DC to RF Conversion (50%+) • High gain >50 dB • CW klystrons typically have a modulating anode for - Gain control - RF drive power in saturation • Power: CW 1 MW, Pulsed 5 MW • Frequencies 300 MHz to 10 GHz+ A. Nassiri CW SCRF workshop 2012 • Intensity modulation of DC beam by control grid • It is highly efficient DC to RF Conversion approaching 70% • Unfortunately low gain 22 dB (max) • Power: CW to 80 kW • Frequencies 300 MHz to 1.5 GHz As a tetrode As a klystron A.
    [Show full text]
  • 100“ 168\A166\1::: 1:1 162 { 164C 1
    US 20060180895Al (19) United States (12) Patent Application Publication (10) Pub. No.: US 2006/0180895 A1 Chen et al. (43) Pub. Date: Aug. 17, 2006 (54) CAPACITOR DEVICE WITH VERTICALLY (21) Appl. No.: 11/055,933 ARRANGED CAPACITOR REGIONS OF VARIOUS KINDS (22) Filed: Feb. 11, 2005 (75) Inventors: Yueh-You Chen, Hsin-Chu City (TW); Publication Classi?cation Chung-Long Chang, Dou-Liu city (TW); Chih-Ping Chao, Chu-Dong (51) Int. Cl. Town (TW); Chun-Hong Chen, Jhubei H01L 29/93 (2006.01) City (TW) (52) U.S. Cl. .......................................... .. 257/595; 257/E2l Correspondence Address: (57) ABSTRACT DUANE MORRIS, LLP IP DEPARTMENT A capacitor device selectively combines MOM, MIM and 30 SOUTH 17TH STREET varactor regions in the same layout area of an IC. TWo or PHILADELPHIA, PA 19103-4196 (US) more types of capacitor regions arranged vertically on a substrate to form the capacitor device. This increase the (73) Assignee: Taiwan Semiconductor Manufacturing capacitance per unit of the capacitor device, Without occu Company, Ltd. pying an extra layout area. 100“ 168\A166\1::: 1:1 162 { 164C 1:: . 160 158, F I /_\~ ’/'_‘\ 130 Bi- - + - +--E6_,154 /\_ A/A\ 128 i. - + - +--?, 152 122 ' 134 . ,/—\ 142 126 \_/—'—~ . + .. +_-\_, 150 /\'_ ‘/_\ 4 124 i. + - +--—2, 148 120% 118/1- ] 116f 108 112 112 104 10s \ p — /_/ 106 _ m _ 114 l_/114 110 Patent Application Publication Aug. 17, 2006 Sheet 2 0f 2 US 2006/0180895 A1 200“ - + - + + - + - - + - + + - + - FIG. 2 300% 316% + ' + 314“ 312% + + 310v“ ' 308 “w - + - + 306\___ 304“ + + FIG. 3 US 2006/0180895 A1 Aug.
    [Show full text]
  • Design of Contactless Capacitive Power Transfer Systems for Battery Charging Applications
    Design of Contactless Capacitive Power Transfer Systems for Battery Charging Applications By DEEPAK ROZARIO A Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Master of Applied Science in The Faculty of Engineering and Applied Sciences Program UNIVERSITY OF ONTARIO INSTITUTE OF TECHNOLOGY APRIL, 2016 ©DEEPAK ROZARIO, 2016 ABSTRACT Several forms for wireless power transfer exists - Microwave, Laser, Sound, Inductive, Capacitive etc. Among these, the Inductive Power Transfer Systems (IPT) are the most extensively used form of wireless power transfer. Due to the utilization of magnetics the inductive power transfer system suffers from Electromagnetic Interference (EMI) issues. Due to the utilization of magnetic field to transfer power, the system is not preferred in an environment with metals and cannot transfer power through metal barriers. Capacitive Power Transfer System (CPT) is an emerging field in the area of wireless power transfer. The antennae of the CPT system, constitute two metal plates which are separated by a dielectric (air). When energised, the metal plates along with the dielectric resemble a loosely coupled capacitor, hence the term capacitive power transfer. The capacitive system utilizes electric field to transfer power and therefore eliminating electromagnetic interference issues. The system has low standing power losses, good anti-interference ability. The advantages, make the CPT system a dynamic alternative to the traditional wireless inductive system. As the area is still in its infancy, the first part of this thesis is dedicated to an extensive study on the literature available on the CPT systems and the basic operation of the system. From, the study it was evident that CPT systems have efficiencies ranging between 60% to 80%.
    [Show full text]
  • Capacitor & Capacitance
    CAPACITOR & CAPACITANCE - TYPES Capacitor types Listed by di-electric material. A 12 pF 20 kV fixed vacuum capacitor Vacuum : Two metal, usually copper, electrodes are separated by a vacuum. The insulating envelope is usually glass or ceramic. Typically of low capacitance - 10 - 1000 pF and high voltage, up to tens of kilovolts, they are most often used in radio transmitters and other high voltage power devices. Both fixed and variable types are available. Vacuum variable capacitors can have a minimum to maximum capacitance ratio of up to 100, allowing any tuned circuit to cover a full decade of frequency. Vacuum is the most perfect of dielectrics with a zero loss tangent. This allows very high powers to be transmitted without significant loss and consequent heating. Air : Air dielectric capacitors consist of metal plates separated by an air gap. The metal plates, of which there may be many interleaved, are most often made of aluminium or silver-plated brass. Nearly all air dielectric capacitors are variable and are used in radio tuning circuits. Metallized plastic film: Made from high quality polymer film (usually polycarbonate, polystyrene, polypropylene, polyester (Mylar), and for high quality capacitors polysulfone), and metal foil or a layer of metal deposited on surface. They have good quality and stability, and are suitable for timer circuits. Suitable for high frequencies. Mica: Similar to metal film. Often high voltage. Suitable for high frequencies. Expensive. Excellent tolerance. Paper: Used for relatively high voltages. Now obsolete. Glass: Used for high voltages. Expensive. Stable temperature coefficient in a wide range of temperatures. Ceramic: Chips of alternating layers of metal and ceramic.
    [Show full text]
  • Operational Amplifier “Op Amp”
    Buffering • You saw that the parallel resistor lowers the voltage • A voltage measurement device with a non-infinite resistance does the same; we would therefore like a way to connect a voltmeter to the touchscreen without loading the system and lowering the voltage • This is easily done using a buffer. A buffer has a high input resistance, but can source the current needed by the load. Energy needed by load from another supply as needed. Input voltage High input reproduced at resistance output • In effect, a buffer (nearly) reproduces the input voltage, but doesn’t load the input • Note that a buffer cannot produce energy, so it draws the energy the load requests from some other power supply 49 Amplifier Integrated Circuits • In an ideal world, an amplifier IC takes an input signal (for example, Vin), and multiplies it by a fixed amount to produce an output signal. Example: Vout = AVVin where AV is the multiplier, called a voltage gain • Of course, the energy for this multiplication has to come from somewhere. Therefore, an amplifier IC has power supply connections as well. 50 Operational Amplifier “Op Amp” • Two input terminals, positive (non- inverting) and negative (inverting) • One output • Power supply V+ , and Op Amp with power supply not shown (which is how we usually display op amp circuits) 51 Equivalent Circuit and Specifications • In other words, a really good buffer, since Ri . All the needed power for the output is drawn from the supply 52 Gain of an Op Amp • Key characteristic of op amp: high voltage gain • Output, A, is
    [Show full text]