Today we are going to learn about relays. Relays are used from a small traffic signal controller to a complex high voltage switchyards. Relays are as like switch for breaking or making a connection, that it can either connect two points or disconnect it. Relays are commonly used to TURN ON and TURN OFF an electronic load. As for that, relays are different types and each one behaves differently as required for its applications. Electromechanical relay is one of the most popularly used relay, we will study more about this in this article.
WHAT IS RELAY:
Relay is the device that can be used to make or break the electrical connections. It is an electrically operated relay. Relays are used where ever it is necessary to control a circuit by an independent low power signal or where all circuits must be controlled by one signal. There are different types of relays and each relay has its own function. The act of transmitting something from one object to another, as defined by the dictionary, it can be applied to these devices also because the signal we received from one side of the device controls the switching operation on other side. Hence, the main function of this device is to make or break the circuit.
CONSTRUCTION OF A RELAY:
Here is the basic information about construction of relay. A core is wounded with copper windings and a movable armature consists of a spring support or stand like structure connected to one end, a metal contact is connected to another side. When the coil has been energized, it attracts the armature. Here the relay has two pins those are Normally closed (NC) and Normally opened (NO). This normally closed pins are connected to the armature and normally opened pins are left free.
WORKING PRINCIPLE OF RELAY:
Now we understand the working of relay under normally opened and closed conditions.
Relay at NORMALLY CLOSED condition:
In the normally closed condition there is not having any applied voltage to the core it can't generate any magnetic field, and it doesn’t act like magnet. So, it cannot attract the movable armature. Therefore, its starting position is connected to armature in normally closed position.
Relay at NORMALLY OPENED condition:
when we applied sufficient voltage to the core, it starts creating magnetic field and acts as magnet. Hence, the movable armature is attracted to the magnetic field which generated by the core, so the position of the armature should be altered.
TYPES OF RELAYS:
Relays are classified based on their applications. There are two types of relays. They are
1) GENERAL PURPOSE RELAYS
2) PROTECTION RELAYS
Again these relays are classified as follows:
GENERAL PURPOSE RELAYS:
- Miniature relays
- Latching relays
- Timer relays
- Contactors
- Machine tool relays
- Hybrid relays
- Smart relays
- Signal relays
- Automobile relays
- PCB relays
PROTECTION RELAYS:
- Thermal overload relays
- Distance protection relays
- Earth fault relays
- Sequence protection relays
- Differential relays
- Electronic relays
Applications of relay:
- Used for the circuit selection if there exists more than one circuit in a system.
- It is used in the traffic signal controllers, temperature controllers.
- To control large power loads in industrial applications
You must be logged in to post a comment.