Electric Relays focuses on the operational and functional aspects rather than on theory and mathematics.

Features:

• Provides a comprehensive survey of the entire range of electric relays with a focus on the practical aspects
• Develops a deep understanding of the design, operation, and applications of relays and their major components
• Covers the entire "world of electrical relays," from reed switch, solid-state, and high-voltage relays to distance, frequency, and microprocessor-based relays
• Includes abundant illustrations, references, and a complete glossary of terms

Contents

History

• Relays and Horses
• From Oersted to Henry
• Art Professor Samuel Morse
• Edison's Relay
• The First Industrial Relays

Magnetic Systems of Elecromagnetic Neutral Relays

• Basic Components of Electromagnetic Relays
• Hysteresis and Coercitive Force
• Types of Magnetic Systems
• Differences Between AC and DC Relays
• Some Auxiliary Elements for Improving the Relay Operation
• What Happens When a Relay is Energized
• Windings of Relays: Types and Design Features

Contact Systems

• Designs of Basic Types of Contacts
• Silver, Gold, Platinum
• Contacts with Two-Stage Commutation
• What is the Purpose of ''Contact Pressure?''
• Self-Cleaning Contacts
• Self-Adjusting Contacts
• When Power Does Not Equal Multiplication by Current and Voltage
• Split Make-Before-Break. High-Frequency Contacts
• Compensation for Shocks and Electro-Dynamic Forces in Contacts
• Sparking Contacts and Their Control
• High-Power Contact Systems
• Mercury Displacement Relays

External Design of Relays

• Environmental Impact on Relays
• Wood and Cardboard: First Protection Shield for Relays
• Is a Sealed Relay Always Better Than Open One?
• Outlets, Terminal Sockets and ''Containers'' for Relays
• Indicators of Operation and Test Buttons
• Relays Which Do Not Look Like Relays at All

Reed Switches and Reed Switch Relays

• Who invented the ''Reed Switch''?
• Coruscation of Ideas and Constructions
• High Power Reed Switches
• Membrane Reed Switches
• Mercury Reed Switches
• High-Voltage Reed Switches
• Reed Switches with Liquid Filling
• Polarized and Memory Reed Switches
• Reed Switch Relays
• Mercury Reed Switch Relays
• Winding-Free Relays

High-Voltage Relays

• What is a ''High-Voltage Relay?''
• Open Relays for High-Voltage Switching
• Vacuum and Gas-Filled High-Voltage Low Power Relays
• High Power Vacuum Relays and Contactors
• High-Voltage Reed Relays
• High-Voltage Interface Relays

Electronic Relays

• Was it Thomas A. Edison Who Invented a Vacuum Light Lamp?
• Lee De Forest Radio Valve: From its First Appearance Until Today
• How a Vacuum Tube Works?
• Relays with Vacuum Valves
• Gas-Tubes with Relay Characteristics
• Power Mercury Valves
• Electron-Beam Switching Tubes
• Semiconductor Relays
• Optoelectronic Relays
• Super-Power Electronic Relays
• Hybrid Relays

Time Relays

• Electromagnetic Time-Delay Relays
• Capacitor Time-Delay Relays
• Relays with Clockwork
• Pneumatic and Hydraulic Time-Delay Relays
• Electronic Time-Delay Relays
• Attachments to Standard Electromagnetic Relays
• Microprocessor Based Time-Delay Relays
• Accelerated (Forced) Relays

Thermal Relays

• Relays Based on a Bimetallic Thermal Element
• Protective Thermal Relays
• Automatic Circuit Breakers with Thermal Elements
• Dilatometer Relays
• Manometric Thermal Relays
• Mercury Thermal Relays
• Thermal Relays with Reed Switches
• Semiconductor Thermal Elements and Thermal Relays

Protective Current and Voltage Relays

• What are ''Protective Relays''
• Current and Voltage Transformers
• Instantaneous Current and Voltage Relays
• Current Relays with an Independent ''Time-Delays'
• Current Relays with Dependent Time-Delay
• Harmonic and Voltage Restraint Relays
• Pulse Current Relays

Power and Power-Directional Relays

• Induction-Type Relays
• Characteristics of Power Direction Relays
• Electro-Dynamic-Type Relays
• Electronic Analogs of Power Direction Relays

Differential Relays

• Principles of Differential Protection
• High-Impedance Differential Relays
• Biased Differential Relays
• Electromagnetic Percentage Differential Relays
• Induction-Type Differential Relays
• Harmonic Restraint Differential Relays
• Pilot-Wire Differential Relays

Distance Relays

• Principles and Basic Characteristics of Distance Protection
• System Swing
• Principles of Distance Relays Construction
• Why do Distance Relays Need ''Memory?''
• Distance Relays with Higher Performance
• Electronic Analogs of Impedance Relays

Frequency Relays

• Why is it Necessary to Control Frequency in Electric Networks?
• Charles Steinmetz: Inventor of the Frequency Relay
• Induction Frequency Relays
• Resonance Relays
• Electronic Frequency Relays

Microprocessor-Based Relays: Prospects and Challenges

• Is It a Relay at All?
• Advantages of Microprocessor-Based ''Relays'
• Disadvantages of Microprocessor-Based ''Relays''

Special Relays

• Polarized Relays
• Latching Relays
• Sequence Relays
• Rotary Relays
• Moving-Coil Relays
• Amplifier-Driven Relays
• Magneto-Hydro-Dynamic Relays
• Annunciator Target Relays
• Flashing-Light Relays
• Buchholz Relays
• Safety Relays
• Ground Fault Relays
• Supervision Relays
• Hydraulic-Magnetic Circuit Breakers

Index

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