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by Paul G. Slade
Electrical Contacts, 2nd Edition
Cover
Half Title
Title Page
Copyright Page
Table of Contents
Preface to the Second Edition
Preface to the First Edition
Introduction
Editor
Contributors
Part I Contact Interface Conduction
1. Electrical Contact Resistance: Fundamental Principles
1.1 Introduction
1.2 Electrical Constriction Resistance
1.2.1 Circular a-spots
1.2.2 Non-Circular and Ring a-Spots
1.2.3 Multiple Contact Spots
1.2.4 Effect of the Shape of Contact Asperity on Constriction Resistance
1.3 Effect of Surface Films on Constriction and Contact Resistance
1.3.1 Electrically Conductive Layers on an Insulated Substrate
1.3.1.1 Calculation of Spreading Resistance in a Thin Film
1.3.2 Electrically Conducting Layers on a Conducting Substrate
1.3.2.1 Electrically Conducting Layers and Thin Contaminant Films
1.3.3 Growth of Intermetallic Layers
1.3.4 Possible Effect of Electromigration on Intermetallic Growth Rates
1.3.5 Electrically Insulating or Weakly Conducting Films
1.3.5.1 Growth Rate and Electrical Resistivity of Oxides of Selected Contact Materials
1.3.6 Fritting of Electrically Insulating Surface Films
1.4 Temperature of an Electrically Heated a-Spot
1.4.1 Voltage–Temperature Relation
1.4.2 Voltage–Temperature Relation with Temperature-Dependent Electrical Resistivity and Thermal Conductivity
1.4.3 The Wiedemann–Franz Law
1.4.4 Temperature Distribution in the Vicinity of an a-Spot
1.4.5 Deviation of the Voltage–Temperature Relation in an Assymetric Contact
1.4.5.1 Case I: Two Metals in Contact
1.4.5.2 Case II: A Metal in Contact with a Non-metal
1.4.6 Special Considerations on the “Melting” Voltage in Electrical Contacts
1.5 Mechanics of a-Spot Formation
1.5.1 Smooth Interfaces
1.5.2 Rough Interfaces
1.6 Breakdown of Classical Electrical Contact Theory in Small Contact Spots
1.6.1 Electrical Conduction in Small a-Spots
1.6.1.1 Contact Resistance
1.6.1.2 Joule Heat Flow through a-Spots
1.6.2 Observations of Breakdown of Classical Electrical Contact Theory in Aluminum Contacts
1.6.2.1 Experimental Data on Aluminum
1.6.3 Observations of Breakdown of Classical Electrical Contact Theory in Gold Contacts
1.6.4 Observations of Breakdown of Classical Electrical Contact Theory in Tin Contacts
1.7 Constriction Resistance at High Frequencies
1.7.1 Skin Depth and Constriction Resistance
1.7.2 Evaluation of Constriction Resistance at High Frequencies
1.7.3 Constriction versus Connection Resistance at High Frequencies
1.8 Summary
Acknowledgments
References
2. Introduction to Contact Tarnishing and Corrosion
2.1 Introduction
2.2 Corrosion Rates
2.3 Corrosive Gases
2.4 Types of Corrosion
2.4.1 Dry Corrosion
2.4.2 Galvanic Corrosion
2.4.3 Pore Corrosion
2.4.4 Creep Corrosion
2.4.5 Metallic Electromigration
2.4.6 Stress Corrosion Cracking
2.4.7 Contacts under Mineral Oil
2.5 Gas Concentrations in the Atmosphere
2.6 Measurements
2.6.1 Weight Gain Measurement
2.6.2 Visual Inspection
2.6.3 Cathodic Reduction
2.6.4 Scanning Electron Microscopy with Energy-Dispersive X-Ray Spectroscopy (SEM/EDAX)
2.6.5 X-Ray Photoelectron Spectroscopy (XPS)
2.6.6 Other Techniques
2.6.7 Contact Resistance Measurements
2.7 Mixed Flow Gas Laboratory Testing
2.8 Electronic Connectors
2.8.1 Background
2.8.2 MFG Test Results
2.9 Power Connectors
2.10 Other Considerations
Acknowledgments
References
3. Gas Corrosion
3.1 Introduction
3.1.1 Scope
3.1.2 Background
3.2 The Field Environments for Electrical Contacts
3.2.1 Environmental Variables
3.2.2 Corrosion Rates
3.2.2.1 Copper and Silver
3.2.2.2 Other Metals
3.2.2.3 Film Effects
3.2.2.4 Shielding Effects
3.2.3 Reactivity Distributions
3.2.3.1 Severity versus Performance
3.2.3.2 Environmental Classes
3.2.3.3 Specifications
3.2.4 Corrosion Mechanisms
3.2.4.1 Silver
3.2.4.2 Copper
3.2.4.3 Nickel
3.2.4.4 Tin
3.2.4.5 Porous Gold Coatings
3.2.4.6 Pore Corrosion
3.2.4.7 Corrosion Product Creep
3.3 Laboratory Accelerated Testing
3.3.1 Objectives
3.3.2 Definition of Acceleration Factor
3.3.3 Historical Background
3.3.4 Single-Gas Corrosion Effects
3.3.4.1 Hydrogen Sulfide
3.3.4.2 Sulfur Dioxide (SO2)
3.3.4.3 Nitrogen Dioxide (NO2)
3.3.4.4 Chlorine
3.3.4.5 Mixed-Gas Sulfur Environments
3.3.4.6 Humidity
3.3.4.7 Temperature
3.3.4.8 Gas Flow Effects
3.3.5 Mixed-Gas Environments
3.3.5.1 Test Systems
3.3.5.2 Monitoring Reactivity
3.3.6 Test Applications
3.3.6.1 Electronic Connectors
3.3.6.2 Mated versus Unmated Exposures
3.3.6.3 Other Considerations
3.4 Lubrication and Inhibition of Corrosion
Acknowledgment
References
4. Effect of Dust Contamination on Electrical Contacts
4.1 Introduction
4.1.1 Background
4.1.2 The Importance of the Dust Problem
4.1.3 The Complexity of the Problem
4.1.4 The Purpose of the Studies
4.2 Dusty Environment and Dust Composition
4.2.1 The Source of Dust
4.2.2 The Collection of the Dust Particles for Testing
4.2.3 The Shape of the Dust Particles
4.2.4 The Identification of the Inorganic Materials
4.2.5 The Organic Materials in Dust
4.2.6 The Water Soluble Salts in Dust
4.3 The Characteristics of Dust Particles
4.3.1 The Electrical Behavior
4.3.1.1 Measurement of the Electric Charge
4.3.1.2 The Electrostatic Attracting Force on the Particle
4.3.2 Mechanical Behavior
4.3.2.1 Load Effect
4.3.2.2 For Stationary Contacts
4.3.2.3 For Sliding Contacts
4.3.2.4 The Effect of Lubricants Coated on Contact Surface
4.3.2.5 Sliding Contacts on Lubricated and Dusty Contacts
4.3.2.6 Fretting (Micro Motion) on Lubricated and Dusty Contacts
4.3.3 Chemical Behavior
4.3.3.1 Dust Particles Create Pores
4.3.3.2 Corrosion Appears as a Result of Dusty Water Solutions
4.3.3.3 Indoor Exposure Results
4.3.3.4 Construction of the Corrosion Stain
4.3.3.5 Fretting Experiments on Dust Corroded Coupon Surfaces…209
4.4 Application Conditions in Dusty Environment
4.4.1 Explanation of the Special Features
4.4.1.1 Covered by Accumulated Small Particles
4.4.1.2 Accumulative Particles Caused by Micro Motion
4.4.1.3 High and Erratic Contact Resistance
4.4.1.4 The Element of Si Causes High Contact Resistance
4.4.1.5 Organics Act as Adhesives
4.4.1.6 Corrosion Products Trap the Dust Particles
4.4.1.7 Difference Between Short Life and Longer Life Contacts
4.4.1.8 Large Pieces of “Stepping Stones”
4.4.1.9 The Performance of Failed Mobile Phones
4.4.2 Other Examples
4.5 Theoretical Analysis of Connector Contact Failure due to the Dust
4.5.1 Two Micro Worlds in Contact
4.5.1.1 Particles Get into the Contact Interface
4.5.2 “Preliminary Attachment”
4.5.2.1 Adhesive Effect
4.5.2.2 Trapping Effect of Corrosion Products
4.5.3 Contact Failure Mechanism
4.5.3.1 Single Particle and Ideal Model
4.5.3.2 Complicated Model – Number of Particles and Morphology of Contact Pairs
4.5.4 Micro Movement
4.5.4.1 Contact Failure
4.6 Future Work
4.6.1 Dust Test for Connectors
4.6.2 Suggestion of the Dust Test
4.6.3 Minimizing the Dust Problem
4.6.3.1 Cleaning the Samples
References
Part II Nonarcing Contacts
5. Power Connectors
5.1 Introduction
5.2 Types of Power Connectors
5.2.1 Plug-and-Socket Connectors
5.2.2 Wire Connectors
5.2.3 Bolted Connectors
5.2.4 Insulation Piercing Connectors
5.3 Properties of Conductor and Connector Materials
5.3.1 Definition of Conductor and Connector Systems
5.3.2 Factors Affecting Conductivity
5.3.2.1 Effect of Temperature
5.3.2.2 Effect of Lattice Imperfections
5.3.2.3 Magnetoresistance
5.3.2.4 Skin Effect
5.3.3 Conductor Materials
5.3.3.1 Copper and Copper Alloys
5.3.3.2 Aluminum and Its Alloys
5.3.4 Materials for Connector Systems
5.3.4.1 Pure Metals and Alloys
5.3.5 Electroplating and Cladding
5.4 Parameters Affecting Performance of Power Connections
5.4.1 Factors Affecting Reliability of Power Connections
5.4.2 Contact Area
5.4.3 Plastic Deformation
5.4.4 Elastic Deformation
5.4.5 Plated Contacts
5.4.6 Oxidation
5.4.7 Corrosion
5.4.7.1 Atmospheric Corrosion
5.4.7.2 Localized Corrosion
5.4.7.3 Crevice Corrosion
5.4.7.4 Pitting Corrosion
5.4.7.5 Pore Corrosion
5.4.7.6 Creep Corrosion
5.4.8 Dust Corrosion
5.4.9 Galvanic Corrosion
5.4.10 Thermal Expansion
5.4.11 Fretting
5.4.11.1 Factors Affecting Fretting
5.4.11.2 Mechanisms of Fretting
5.4.11.3 Examples of Fretting Damage in Power Connections
5.4.11.4 Compression Connectors
5.4.11.5 Bus-Stab Contacts
5.4.11.6 Plug-In Connectors
5.4.11.7 Bolted Connections
5.4.11.8 Fretting in Aluminum Connections
5.4.11.9 Effect of Electrical Current
5.4.11.10 Fretting in Coatings (Platings)
5.4.11.11 Fretting in Circuit Breaker Contact Materials
5.4.12 Intermetallic Compounds
5.4.13 Intermetallics in Copper–Tin Systems
5.4.13.1 Example of Intermetallics Formation in Power Connections
5.4.14 Stress Relaxation and Creep
5.4.15 Nature of the Effect of Electric Current
5.4.16 Effect of Electric Current on Stress Relaxation
5.4.17 Creep
5.5 Palliative Measures
5.5.1 Contact Area
5.5.2 Contact Pressure
5.5.3 Mechanical Contact Device
5.5.4 Disc-Spring (Belleville) Washers
5.5.5 Wedge Connectors
5.5.6 Automatic Splices
5.5.7 Dead-end Connectors
5.5.8 Shape-Memory Alloy Connector Devices
5.5.9 Coating (Plating)
5.5.10 Lubrication—Contact Aid Compounds
5.5.11 Bimetallic Inserts
5.5.12 Transition Washers
5.5.13 Multilam Contact Elements
5.5.14 Welded Connections
5.5.14.1 Thermite (Exothermic) Welding
5.5.14.2 Friction Welding
5.5.14.3 Explosion Welding
5.5.14.4 Resistance Welding
5.5.14.5 Resistance Brazing
5.5.15 Connector Design
5.5.15.1 Fired Wedge-Connectors
5.5.15.2 Stepped Deep Indentation Connectors
5.6 Connector Degradation
5.6.1 Economical Consequences of Contact Deterioration
5.6.2 Power Quality
5.7 Prognostic Models
5.7.1 Prognostic Model 1 for Contact Remaining Life
5.7.2 Prognostic Model 2 for Contact Remaining Life
5.7.3 Physical Model
5.8 Shape-Memory Alloys (SMA)
5.8.1 Origin of Shape-Memory Effect
5.8.1.1 One-Way Memory Effect
5.8.1.2 Two-Way Memory Effect
5.8.2 Applications of SMA in Power Connections
5.8.3 Electrical Connections
5.8.4 Temperature Indicators
5.9 Metal Foam Materials
5.9.1 Aluminum Foam Materials
5.9.1.1 Electrical and Thermal Properties of Foam Materials
5.9.1.2 Power Connection Applications
5.9.2 Copper Foam Materials
5.9.2.1 Applications of Copper Foam Materials
5.9.3 Silver Foam Materials
5.10 Installation of Power Connections
5.10.1 Examples of Improper Installations
5.11 Accelerated Current-Cycling Tests (Standards)
5.11.1 Present Current-Cycling Tests
References
6. Low-Power Commercial, Automotive, and Appliance Connections
6.1 Introduction
6.2 Connectors
6.2.1 Functional Requirements
6.2.2 Types of Connectors
6.2.3 Mechanical Considerations
6.3 Contact Terminals
6.3.1 Contact Physics
6.3.2 Terminal Types
6.3.3 Other Electrical Contact Parameters
6.4 Degradation of Connector Contact
6.4.1 Surface Films
6.4.2 Fretting Corrosion of Tin–Plated Contacts
6.4.3 Examples of Contact Failures
6.4.3.1 Automotive Position Sensor Connector
6.4.3.2 Fuel Injector Connector
6.4.3.3 Glowing Contacts
6.4.3.4 Electrolytic Corrosion
6.4.3.5 Incompatible Plating and Low Contact Force
6.5 Automotive Connector Contacts
6.5.1 Vehicle Conditions
6.5.2 High Power Connectors for Electric and Hybrid Vehicles
6.5.3 Aluminum Wiring Connections
6.5.4 Connections for High-Vibration Environment
6.6 Summay
References
7. Tribology of Electronic Connectors: Contact Sliding Wear, Fretting, and Lubrication
7.1 Introduction
7.2 Sliding Wear
7.2.1 Early Studies
7.2.2 Adhesion
7.2.2.1 “Wiping” Contaminant from Contact Surfaces
7.2.2.2 Mild and Severe
7.2.2.3 Prow Formation
7.2.2.4 Rider Wear
7.2.2.5 Gold Platings: Intrinsic Polymers and Junction Growth
7.2.2.6 Electroless Gold Plating
7.2.3 Abrasion
7.2.4 Brittle Fracture
7.2.5 Delamination and Subsurface Wear
7.2.6 Effect of Underplate and Substrate
7.2.6.1 Hardness
7.2.6.2 Roughness
7.2.7 Electrodeposited Gold: Relationship of Wear to Underplate Hardness
7.2.7.1 Hardener Metal Content
7.2.8 Clad Metals
7.2.9 Tin and Tin–Lead Alloys
7.2.10 Silver
7.3 Fretting
7.3.1 Background
7.3.2 Fretting Regimes
7.3.3 Static versus Dynamic Contact Resistance
7.3.4 Field and Laboratory Testing Methodologies
7.3.4.1 Generation of Fretting Displacement
7.3.4.2 Determination of Contact Resistance
7.3.5 Materials Studies
7.3.5.1 Apparatus
7.3.5.2 Metals Having Little or No Film-Forming Tendency
7.3.5.3 Non-Noble Metals/Fretting Corrosion
7.3.5.4 Frictional Polymer-Forming Metals
7.3.5.5 Dissimilar Metals on Mating Contacts
7.3.6 Wear-Out Phenomena
7.3.6.1 Gold-Based Systems
7.3.6.2 Palladium-Based Systems
7.3.6.3 Tin and Tin–Lead Alloy Systems
7.3.6.4 Role of Underplate and Substrate
7.3.7 Parametric Studies
7.3.7.1 Cycle Rate
7.3.7.2 Wipe Distance
7.3.7.3 Force
7.3.8 Environmental Effects
7.3.9 Thermal
7.3.10 Effect of Current
7.3.11 Surface Finish and Contact Geometry
7.3.12 Material Transfer, Wear, Film Formation, and Contact Resistance
7.3.12.1 Summary of Physical Processes
7.4 Lubrication
7.4.1 Introduction
7.4.2 Metallic Films
7.4.2.1 Principles of Metallic Film Lubrication
7.4.2.2 Sliding and Wiping Contacts
7.4.2.3 Fretting Contacts
7.4.3 Fluid Lubricants
7.4.3.1 Background
7.4.3.2 Some Fundamental Properties of Lubricants
7.4.3.3 Requirements
7.4.3.4 Types of Fluid Lubricants: A Sliding Contact Investigation
7.4.3.5 Control of Fretting Degradation
7.4.4 Grafted and Self-Assembled Lubricant Layers
7.4.5 Greases and Solid Lubricants
7.4.5.1 Greases
7.4.5.2 Solids
7.4.6 Lubricant Durability
7.4.7 Other Considerations
References
8. Materials, Coatings, and Platings
8.1 Introduction
8.1.1 Scope
8.1.2 Requirements of Contact Finishes and Coatings
8.1.3 Terminology
8.2 Metallic Finishes
8.2.1 Wrought Metals
8.2.2 Electrodeposits and Electroless Deposits
8.2.2.1 Thickness of Platings
8.2.2.2 Plating Hardness
8.2.2.3 Classification of Platings
8.2.3 Contact Finishes Produced by Non-Chemical Methods
8.2.4 Metal-in-Elastomer Materials
8.2.5 Overview
8.3 Properties Related to Porosity
8.3.1 Origins of Porosity
8.3.2 Tests of Porosity
8.3.3 Relationships between Porosity, Thickness of Finish, and Substrate Roughness
8.3.4 Effect of Underplatings, Flash Coatings, and Strikes on the Porosity of Electrodeposits
8.3.5 Reduction in the Chemical Reactivity of Finishes by the Use of Underplates
8.4 Metallurgical and Structural Properties
8.4.1 Thermal Diffusion
8.4.2 Intermetallics
8.4.3 Tin Whiskers
8.4.4 Silver Whiskers
8.5 Physical and Mechanical Properties
8.5.1 Characteristics of Layered Systems
8.5.1.1 Hardness
8.5.1.2 Contact Resistance
8.5.2 Topography
Acknowledgement
References
Part III The Electric Arc and Switching Device Technology
9. The Arc and Interruption
9.1 Introduction
9.2 The Fourth State of Matter
9.3 Establishing an Arc
9.3.1 Long-Gap Gas Breakdown
9.3.2 Vacuum Breakdown and Short-Gap Breakdown
9.3.3 The Volt–Current Characteristics of Separated Contacts
9.4 The Formation of the Electric Arc
9.4.1 The Formation of the Electric Arc during Contact Closing
9.4.2 The Formation of the Electric Arc during Contact Opening
9.5 The Arc in Air at Atmospheric Pressure
9.5.1 The Arc Column
9.5.2 The Cathode Region
9.5.3 The Anode Region
9.5.4 The Minimum Arc Current and the Minimum Arc Voltage
9.5.5 Arc Volt–Ampere Characteristics
9.6 The Arc in Vacuum
9.6.1 The Diffuse Vacuum Arc
9.6.2 The Columnar Vacuum Arc
9.6.3 The Vacuum Arc in the Presence of a Transverse Magnetic Field
9.6.4 The Vacuum Arc in the Presence of an Axial Magnetic Field
9.7 Arc Interruption
9.7.1 Arc Interruption in Alternating Current Circuits
9.7.1.1 Stage 1 - Instantaneous Dielectric Recovery
9.7.1.2 Stage 2 - Decay of the Arc Plasma and Dielectric Reignition
9.7.1.3 Thermal Reignition
9.7.2 Arc Interruption in Direct Current Circuits
9.7.3 Vacuum Arc Interruption in Alternating Circuits
9.7.4 Arc interruption of Alternating Circuits: Current Limiting
9.7.5 Interruption of Low Frequency and High Frequency Power Circuits
9.7.6 Interruption of Megahertz and Gigahertz Electronic Circuits
Acknowledgments
References
10. The Consequences of Arcing
10.1 Introduction
10.2 Arcing Time
10.2.1 Arcing Time in an AC Circuit
10.2.2 Arcing Time in a DC Circuit
10.2.3 Activation of the Contact
10.2.4 Arcing Time in Very Low-Current DC Circuits: Showering Arcs
10.3 Arc Erosion of Electrical Contacts
10.3.1 Erosion on Make and Erosion on Break
10.3.2 The Effect of Arc Current
10.3.3 The Effect of Contact Size
10.3.4 Determination of Contact Size in AC Operation
10.3.5 Erosion of Contacts in Low-Current DC Circuits
10.3.6 Erosion of Contacts in Low-Current AC Circuits
10.4 Blow-Off Force
10.4.1 Butt Contacts
10.5 Contact Welding
10.5.1 Welding of Closed Contacts
10.5.2 Welding during Contact Closure
10.5.3 Welding as Contacts Open
10.6 Changes in the Contact Surface as a Result of Arcing
10.6.1 Silver–Based Contacts
10.6.2 Silver–Refractory Metal Contacts
10.6.3 Other Ambient Effects on the Arcing Contact Surface: Formation of Silica and Carbon and Contact Activation
Acknowledgments
References
11. Reed Switches
11.1 Principles and Design of the Reed Switch
11.1.1 Pull-In Characteristics of a Reed Switch
11.1.2 Drop-Out Characteristics of a Reed Switch
11.1.3 Magnet Drive Characteristics of a Reed Switch
11.1.3.1 X–Y Characteristic H (Horizontal)
11.1.3.2 X–Z Characteristic H (Horizontal)
11.1.3.3 X–Y Characteristic V (Vertical)
11.2 Recommended Contact Plating
11.2.1 Materials for Contact Plating
11.2.2 Ground Plating
11.2.3 Rhodium Plating
11.2.4 Ruthenium Plating
11.2.5 Other Platings
11.2.5.1 Copper Plating
11.2.5.2 Tungsten Plating
11.2.5.3 Rhenium Plating
11.2.5.4 Iridium Plating
11.2.5.5 Nitriding the Permalloy (Ni-Fe [48 wt%]) Blade Material
11.3 Contact Surface Degradation and Countermeasures
11.3.1 Surface Deactivation Treatment
11.3.1.1 Life Test of Samples Left for 24 Hours after Sealing
11.3.1.2 Life Test of Samples Left for One Week after Sealing
11.3.1.3 Life Test of Samples Left for One Month after Sealing
11.3.1.4 Life Test of Samples Left for Three Months, Six Months, and One Year after Sealing
11.3.2 Prevention of Contact Adhesion
11.4 Applications of Reed Switches
11.4.1 Reed Relays
11.4.2 Applications of Magnetic-Driven Reed Switches
References
12. Low Current and High Frequency Miniature Switches: Microelectromechanical Systems (MEMS), Metal Contact Switches
12.1 Introduction
12.1.1 Common MEMS Actuation Methods
12.2 Micro-Contact Resistance Modeling
12.3 Contact Materials for Performance and Reliability
12.4 Failure Modes and Reliability
12.5 Conclusion
References
13. Low Current Switching
13.1 Introduction and Device Classification
13.2 Device Types
13.2.1 Hand-Operated Switches
13.2.1.1 The Rocker Switch Mechanism
13.2.1.2 Lever Switches
13.2.1.3 Slide Switches
13.2.1.4 Rotary Switches
13.2.1.5 Push-Button Switches
13.2.1.6 Switching Devices Used below 0.5 A
13.2.2 Actuated Switches
13.2.2.1 Limit Switches
13.2.2.2 Thermostatic Controls
13.2.2.3 Electro-Mechanical Relay
13.3 Design Parameters for Static Switching Contacts
13.3.1 Small-Amplitude Sliding Motion
13.3.2 Contact Force and Contact Materials
13.3.2.1 Contacts at Current Levels below 1 A
13.3.2.2 Contacts at Current Levels between 1 and 30 A
13.3.2.3 Contact Force
13.4 Mechanical Design Parameters
13.4.1 Case Study (1): Hand-Operated Rocker-Switch Mechanism
13.4.1.1 Moving-Contact Dynamics of a Rocker-Switch Mechanism
13.4.1.2 Design Optimization of a Rocker-Switch Mechanism
13.4.2 The Opening Characteristics of Switching Devices
13.4.2.1 Moving Contact Dynamics at Opening
13.4.3 The Make Operation
13.4.3.1 Impact Mechanics
13.4.3.2 The Coefficient of Restitution
13.4.3.3 Impact Mechanics for a Pivoting Mechanism
13.4.3.4 The Velocity of Impact
13.4.3.5 Bounce Times
13.4.3.6 Total Bounce Times
13.4.3.7 Impact Times
13.4.3.8 Design Parameters for the Reduction of Contact Bounce
13.5 The Measurement of Contact Wear and Contact Dynamics
13.5.1 The Measurement of Contact Surfaces
13.5.2 Three Dimensional (3-D) Surface Measurement Systems
13.5.2.1 Contact Systems
13.5.2.2 Non-Contact Systems
13.5.3 Case Study (2): Example of Volumetric Erosion
13.5.4 The Measurement of Arc Motion and Contact Dynamics
13.6 Electrical Characteristics of Low-Current Switching Devices at Opening
13.6.1 Low-Current DC Arcs
13.6.1.1 Arc Voltage Characteristics
13.6.1.2 Voltage Steps below 7 A
13.6.1.3 Case Study (3): Arc Voltage, Current and Length under Quasi-Static Conditions for Ag/CdO Contacts
13.6.1.4 Opening Speed and Arc Length
13.6.1.5 Case Study (4): Automotive Systems
13.6.2 DC Erosion
13.6.2.1 Ag and Ag/MeO Contact Erosion/Deposition
13.6.3 Low-Current AC Arcs
13.6.3.1 Typical Waveforms and Arc Energy
13.6.4 AC Erosion
13.6.4.1 Point-on-Wave (POW) Studies Using Ag/CdO Contact Materials
13.7 Electrical Characteristics of Low Current Switching Devices at Closure
13.7.1 Contact Welding on Make
13.7.2 Reducing Contact Bounce
13.7.3 Pre-Impact Arcing
13.7.4 Influence of Velocity during the First Bounce
13.7.4.1 The First Bounce
13.7.5 Bounces after the First
13.7.6 Summary of Contact Bounce
13.8 Summary
13.8.1 Switch Design
13.8.2 Break Operation
13.8.2.1 DC Operation
13.8.2.2 AC Operation
13.8.3 Make Operation
13.8.3.1 Design Parameters
13.8.3.2 Reducing Contact Bounce
13.8.3.3 Arcing during the Bounce Process
Acknowledgments
References
14. Medium to High Current Switching: Low Voltage Contactors and Circuit Breakers, and Vacuum Interrupters
14.1 General Aspects of Switching in Air
14.1.1 Arc Chutes
14.1.2 Magnetic Blast Field
14.1.3 Arc Dwell Time on the Contacts
14.1.4 Sticking and Back-Commutation of the Arc
14.2 Contacts for Switching in Air
14.3 Low-Voltage Contactors
14.3.1 Principle/Requirements
14.3.2 Mechanical Arrangement
14.3.3 Quenching Principle and Contact and Arc Chute Design
14.3.4 Contact Materials
14.3.5 Trends
14.3.5.1 Contactors versus Electronics
14.3.5.2 Vacuum Contactors
14.3.5.3 Hybrid Contactors
14.3.5.4 Integration with Electronic Systems
14.4 Low-Voltage Circuit-Breakers and Miniature Circuit-Breakers
14.4.1 Principle/Requirements
14.4.2 General Arrangement
14.4.3 Quenching Principle and Design of Arc Chute and Contact System
14.4.3.1 Quenching Principles
14.4.3.2 Arc Chute and Contact Arrangement
14.4.4 Trip System
14.4.5 Examples of Miniature Circuit-Breakers
14.4.6 Contact Materials
14.4.7 Special Requirements for DC Switching
14.4.8 Current Limitation by Principles Other than Deion Arc Chutes
14.4.8.1 Arcs Squeezed in Narrow Insulating Slots
14.4.8.2 Reversible Phase Changes of Liquid or Low-Melting Metal
14.4.8.3 Temperature-Dependent Ceramics or Polymers
14.4.8.4 Contact Resistance between Powder Grains
14.4.8.5 Superconductors
14.5 Simulations of Low-Voltage Switching Devices
14.5.1 Simulation of Low-Voltage Arcs
14.5.1.1 General Principle of Simulation
14.5.1.2 Arc Roots on Cathode and Anode
14.5.1.3 Radiation
14.5.1.4 Interaction between Arc and Electrode or Wall Material (Ablation)
14.5.1.5 Plasma Properties
14.5.1.6 Simplification by Porous Media
14.5.2 Further Simulations of Contact and Switching Device Behavior
14.6 Vacuum Interrupters
14.6.1 Principle/Applications
14.6.2 Design
14.6.3 Recovery and the Influence of the Design
14.6.4 Contact Materials for Vacuum Interrupters and Their Influence on Switching
14.6.4.1 Requirements
14.6.4.2 Arc Interruption
14.6.4.3 Interruption of High Frequency Transients
14.6.4.4 Current Chopping
14.6.5 Simulation of Arcs in Vacuum Interrupters
References
15. Arc Faults and Electrical Safety
15.1 Introduction
15.2 Arc Fault Circuit Interrupters (AFCIs)
15.3 Arcing Faults
15.3.1 Short-Circuit Arcing
15.3.2 Series Arcing
15.4 Glowing Connections
15.5 Arcing Fault Properties
15.5.1 Frequency
15.5.2 Electrode Materials
15.5.3 Arc Fault Current
15.5.4 Cable Impedance and Cable Length Effects
15.6 Other Types of Arcing Faults
15.7 Conclusions
References
Part IV Arcing Contact Materials
16. Arcing Contact Materials
16.1 Introduction
16.2 Silver Metal Oxides
16.2.1 Types
16.2.2 Manufacturing Technology
16.2.2.1 Internal Oxidation
16.2.2.2 Post-Oxidized Internally Oxidized Parts (Process B 1.0)
16.2.2.3 One-Sided Internally Oxidized Parts (Process B 2.01)
16.2.2.4 Preoxidized Internally Oxidized Parts (Process B.2.02)
16.2.2.5 Powder Metallurgical (PM) Silver Metal Oxides (Processes C and D)
16.2.3 Electrical Performance Factors
16.2.3.1 AC versus DC Testing
16.2.3.2 High Current Inrush DC Automotive and AC Loads
16.2.3.3 Inductive Loads
16.2.3.4 Silver–Tin Oxide Type Materials and Additives
16.2.3.5 Material Factor
16.2.3.6 Interpreting Material Research, Example from Old Silver Cadmium Oxide Research
16.2.4 Material Considerations Based on Electrical Switching Characteristics
16.2.4.1 Erosion/Materials Transfer/Welding
16.2.5 Transfer/Welding
16.2.6 Erosion/Mechanisms/Cracking
16.2.7 Erosion/Arc Mobility
16.2.8 Interruption Characteristics
16.2.9 Contact Resistance
16.2.9.1 Summary Metal Oxides
16.3 Silver Refractory Metals
16.3.1 Manufacturing Technology
16.3.1.1 Manufacturing Technology/Press Sinter Repress (Process D 1.0)
16.3.2 Material Technology/Extruded Material
16.3.2.1 Material Technology/Liquid Phase Sintering (Process D 2.0)
16.3.2.2 Material Technology/Press Sinter Infiltration (Process D 3.0)
16.3.3 Metallurgical/Metallographic Methods
16.3.3.1 Metallurgical/Metallographic Methods/Preparation
16.3.3.2 Metallurgical/Metallography/Quantitative Analysis
16.3.4 Metallurgical/Structure/Strength and Toughness
16.3.5 Electrical Properties (EP)
16.3.5.1 EP/Arc Erosion/Microstructure and Properties
16.3.5.2 EP/Arc Erosion/Silver Refractory
16.3.5.3 EP/Graphite Additions to Silver Tungsten and Silver Tungsten Carbide
16.3.5.4 EP/Copper Refractory Metals
16.3.5.5 EP/Erosion/Summary
16.3.5.6 EP/Composite Refractory Materials/Contact Resistance
16.4 Vacuum Interrupter Materials
16.5 Tungsten Contacts
16.6 Non-Noble Silver Alloys
16.6.1 Fine Silver
16.6.2 Hard Silver and Silver–Copper Alloys
16.7 Silver–Nickel Contact Materials
16.8 Silver Alloys and Noble Metals
16.8.1 Palladium and Silver–Palladium Alloys
16.8.2 Platinum
16.9 Silver–Graphite Contact Materials
16.10 Conclusion
Acknowledgements
References
17. Contact Design and Attachment
17.1 Introduction
17.1.1 Arc-Induced Contact Stresses and Interface Bond Quality
17.2 Staked Contact Assembly Designs
17.2.1 Contact Rivets
17.2.1.1 Solid Rivets
17.2.1.2 Machine-Made Composite Rivets
17.2.1.3 Brazed Composite Rivets
17.2.1.4 Rivet Staking
17.3 Welded Contact Assembly Designs
17.3.1 Resistance Welding
17.3.1.1 Button Welding
17.3.1.2 Wire-Welding
17.3.1.3 Contact Tape Welding
17.3.2 Special Welding Methods
17.3.2.1 Percussion Welding
17.3.2.2 Ultrasonic Welding of Contacts
17.3.2.3 Friction Welding of Contacts
17.4 Brazed Contact Assembly Designs
17.4.1 Methods for Brazing Individual Parts
17.4.1.1 Torch Brazing
17.4.1.2 Induction Brazing
17.4.1.3 Direct and Indirect Resistance Brazing
17.4.1.4 Furnace Brazing
17.4.1.5 Continuous Laminated Strip Brazing, “Toplay”
17.4.1.6 Brazed Assembly Quality Control Methods
17.5 Clad Metals, Inlay, and Edge Lay
17.6 Contact Alloys for Non-Arcing Separable Contacts
17.6.1 Gold and Gold Alloys
17.6.2 Manufacturing Technology
17.6.3 Physical and Chemical Properties
17.6.4 Metallurgical Properties
17.6.5 Contact Applications and Performance
Acknowledgments
References
18. Electrical Contact Material Testing Design and Measurement
18.1 Objectives
18.2 Device Testing and Model Switch Testing
18.2.1 Device Testing
18.2.2 Model Switch Testing
18.3 Electrical Contact Testing Variables
18.3.1 AC versus DC Testing
18.3.2 Switching Load Type
18.3.3 Opening and Closing Velocity Effects
18.3.4 Contact Bounce
18.3.5 Contact Carrier Mass and Conductivity
18.3.6 Contact Closing Force and Over Travel
18.3.7 Enclosed and Open Contact Devices
18.3.8 Testing at Different Ambient Temperatures
18.3.9 Erosion Measurement
18.3.10 Summary Electrical Contact Testing Variables
18.4 Electrical Testing Result Types and Measurement Methods
18.4.1 Contact Resistance
18.4.1.1 Model Testing
18.4.1.2 Evaluation and Presentation of Results
18.4.2 Contact Bounce Measurement
18.4.2.1 Model Testing
18.4.2.2 Evaluation
18.4.3 Contact Welding Measurement
18.4.3.1 Weld Strength Measured
18.4.4 Contact Erosion Measurements
18.4.4.1 Accelerated and Model Testing
18.4.4.2 Extrapolation at Rated Stress
18.4.4.3 Increase of the Switching Frequency
18.4.4.4 Testing at Increased Electrical Load
18.4.4.5 Fixed-Gap Models
18.4.4.6 Moving Contact Models
18.4.4.7 Evaluation and Presentation of Results
18.4.5 AC Arc Reignition Measurement
18.4.6 Arc Motion Measurements
18.4.6.1 Measurement
18.4.6.2 Electronic Optical
18.4.6.3 Model Switch Arc Motion Control
18.4.6.4 Evaluation and Presentation of Results
18.4.7 Arc-Wall Interaction Measurements
References
19. Arc Interactions with Contaminants
19.1 Introduction
19.2 Organic Contamination and Activation
19.2.1 The Phenomena
19.2.2 Sources of Organic Vapors
19.2.3 Processes of Contact Activation
19.2.4 Activation Effects
19.2.5 Activation and Contact Resistance Problems
19.2.6 Methods for Detecting Carbon Contamination
19.3 Mineral Particulate Contamination of Arcing Contacts
19.4 Silicone Contamination of Arcing Contacts
19.4.1 Contamination from Silicone Vapors
19.4.2 Contamination from Silicone Migration
19.4.3 Summary of Silicone Contamination Mechanisms
19.5 Lubricants with Refractory Fillers
19.6 Oxidation of Contact Materials
19.7 Resistance Effects from Long Arcs
Acknowledgments
References
Part V Sliding Electrical Contacts
20. Sliding Electrical Contacts (Graphitic Type Lubrication)
20.1 Introduction
20.2 Mechanical Aspects
20.2.1 Hardness
20.2.2 Friction and Wear
20.2.3 Tunnel Resistance and Vibration
20.3 Chemical Aspects
20.3.1 Oxidation
20.3.2 Moisture Film
20.4 Electrical Effects
20.4.1 Constriction Resistance
20.4.2 Film Resistance
20.4.3 Fundamental Aspects of Commutation
20.4.4 Equivalent Commutation Circuit and DC Motor Driving Automotive Fuel Pump
20.4.5 Arc Duration and Residual Current
20.5 Thermal Effects
20.5.1 Steady State
20.5.2 Actual Temperature
20.5.3 Thermal Mound
20.6 Brush Wear
20.6.1 Holm’s Wear Equation
20.6.2 Flashes and Smutting
20.6.3 Polarities and Other Aspects
20.7 Brush Materials and Abrasion
20.7.1 Electro- and Natural Graphite Brushes
20.7.2 Metal Graphite Brush and Others
20.8 Summary
References
21. Illustrative Modern Brush Applications
21.1 Introduction
21.2 Brush Materials
21.2.1 Electrographite
21.2.2 Carbon-Graphite
21.2.3 Graphite
21.2.4 Resin-Bonded
21.2.5 Metal-Graphite
21.2.6 Altitude-Treated Brushes
21.3 Brush Applications
21.3.1 Minature Motors
21.3.2 Fractional Horsepower Motors
21.3.2.1 Wound Field/Permanent Magnet-Motor Characteristics
21.3.3 Automotive Brush Applications
21.3.3.1 Auxiliary Motors
21.3.3.2 Alternators
21.3.3.3 Starter Motors
21.3.4 Industrial Brushes
21.3.5 Diesel Electric Locomotive Brushes
21.3.6 Aircraft and Space Brushes
21.3.7 Brush Design
22. Sliding Contacts for Instrumentation and Control
22.1 Introduction
22.2 Sliding Contact—The Micro Perspective
22.2.1 Mechanical Aspects
22.2.2 Motion Initiation (Pre-Sliding)
22.2.3 Friction Forces
22.2.4 Motion Continuation
22.2.5 Adhesion
22.2.6 Adhesive Transfer
22.2.7 Plowing, or “Two-Body,” Abrasion
22.2.8 Hard Particle, or “Three-Body,” Abrasion
22.2.9 Motion Over Time
22.3 Electrical Performance
22.3.1 Contact Resistance Variation (Noise)
22.3.2 Non-Ohmic Noise
22.3.3 Non-Linear Noise (Frequency Dependent)
22.3.4 Contact Impedance
22.3.5 Data Integrity
22.4 Micro-Environment of Contact Region
22.4.1 Film Forming on the a-Spots
22.4.2 Unintentional Contamination
22.4.2.1 Particulates
22.4.2.2 Contamination or “Air Pollution”
22.4.2.3 Organic Off-Gasses
22.4.2.4 Friction Polymers
22.4.3 Lubrication (Intentional Contamination)
22.4.4 Lubrication Modes (Anaerobic and Aerobic)
22.4.4.1 Anaerobically Lubricated Contacts
22.4.4.2 Aerobically Lubricated Contacts
22.4.4.3 Temperature Extremes
22.4.4.4 Submerged in Flammable Fuels
22.4.4.5 Low-Pressure/Vacuum Operation
22.4.4.6 Vapor and Gas Lubrication
22.5 Macro Sliding Contact
22.5.1 Counterface Configuration
22.5.1.1 Flat Surfaces
22.5.1.2 Cylindrical Surfaces
22.5.1.3 Counterface Contact Shapes
22.5.2 Real versus Apparent Area of Contact
22.5.3 Brush Configurations
22.5.3.1 Cartridge Brush
22.5.3.2 Cantilever Composite Brush
22.5.3.3 Cantilever Metallic Finger
22.5.3.4 Cantilever Wire Brush
22.5.3.5 Multifilament or Fiber Brush
22.5.3.6 Benefits of Multiple Brushes
22.5.4 Forces on the Brush
22.6 Materials for Sliding Contacts
22.6.1 Materials for Counterfaces
22.6.2 Solid Lubricated Composite Materials for Brushes
22.6.3 Wire Brush Materials Criteria
22.7 Friction and Wear Characteristics
22.7.1 Friction
22.7.2 Wear
22.8 Contact Parameters and Sliding-Contact Assemblies
22.8.1 Contact Noise
22.8.2 Slip Rings as Transmission Lines
22.8.3 Results of Normal Operation
22.9 Future
22.10 Summary
Acknowledgments
References
23. Metal Fiber Brushes
23.1 Introduction
23.1.1 Fiber Brushes for Power
23.1.2 Diversification of Applications
23.1.3 Outline of Chapter
23.2 Sliding Wear of Multi-Fiber Brushes
23.2.1 Adhesive Wear
23.2.2 Holm-Archard Wear Equation
23.2.3 Low Wear Equilibrium
23.2.4 High Wear Regime
23.2.5 Plastic and Elastic Contact
23.2.6 Critical or Transition Brush Pressure
23.2.7 Wear of Fiber Brushes
23.2.8 Effects of Sliding Speed
23.2.9 Effect of Arcing and Bridge Transfer
23.3 Surface Films, Friction, and Materials Properties
23.3.1 Thin Film Behavior
23.3.2 Water Molecules
23.3.3 Film Disruption
23.3.3 Lubrication
23.4 Electrical Contact
23.4.1 Dependence of Electrical Resistance on Fiber Brush Construction
23.5 Brush Dynamics
23.5.1 Speed Effect
23.6 Future
23.7 Summary
Acknowledgments
References
Part VI Contact Data
24. Useful Electric Contact Information
24.1 Introduction
24.2 Notes to the Tables
References
Author Index
Subject Index
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