HISTORY
Relays and Horses
From Oersted to Henry
Art Professor Samuel Morse
Edison's Relay
The First Industrial Relays
MAGNETIC SYSTEMS OF ELECTROMAGNETIC 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 RELAY
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''
Summing Up
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
BASIC RELAY TERMS AND DEFINITIONS: GLOSSARY
REFERENCES