Knowledge of the expert
The relay is a well known and widely used component. Applications range from classic panel built control systems to modern inrefaces between control microprocessors and their power circuits or any application where reliable galvanic separation is required between different circuits. Altough considered to be a relatively simple component, the electromechanical relay and its technology is complex and often misundestood.
History of relay
The earliest electrical relays were developed in the 1830s, as people began to recognize that such switches could be extremely useful. Historically, electrical relays were often made with electromagnets, which continue to be used today, although for some applications solid state relays are preferred. They key difference between electromagnetic and solid state options is that electromagnetic relays have moving parts, and solid state relays do not. Electromagnets also conserve more energy than their solid state counterparts do.
Usage of relay
One of the reasons an electrical relay is such a popular tool for electricians and engineers is that it can control electrical output which is higher than the electrical input it receives. In the example discussed above, if the ignition connected directly to the battery, heavy duty insulated wiring would be needed to connect the steering column to the battery, and the ignition switch would also need to be much more robust. By using a relay, relatively lightweight wiring can be used, saving space and increasing vehicle safety.
A variety of circuits can be connected to an electrical relays. Relays can be used as amplifiers for electrical energy, as in the car example, and they can also connect to things like alarm switches, activating when a circuit is broken to trigger an alarm. Many electrical failsafe systems utilize electrical relays which turn on or off in response to things like a current overload, irregular current, and other issues which may arise. These electrical relays trip to shut the system down until the problem can be addressed.
All documents, software and books are free to download and preserved only to registered users. Login and registration links are located at the top of the portal or use links below.
Relay book
Protection Relays
| No. | Description | Download |
| 1 | Relay Selection Guide | |
| 2 | Distance Relay Fundamentals | |
| 3 | Line Protection With Distance Relays | |
| 4 | Electrical Relay Diagram and P&ID Symbols  | |
| 5 | The philosophy of protective relaying |
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Gilmar
Congratulations for this website .
Gilmar
São Paulo -Brazil
Edvard
Thank you Gilmar! Me and my team did a great efforts to make EEP to be like it is now.
BR,
harjit
dear u really did great job ., i just want to know that ,can you provide me some elecrical formules for calculation for relay , like for didtance protection relay , or diff. protection relay
thnx a lot
Edvard
Thank you for kind words Harjit! I wrote down your request, and I’ll try to find something.
BR
seanmoo
Just joined after seeing reference on Linkedin and really impressed by the sites contents. Great work.
Sean
nilesh.parmar9@yahoo.co.uk
You have done a excellent job. This website is very useful for begineers and even for expert as well.
Vinay Kumar
Good Job boss, really inspired especially application enginners like us….