Due to the relay coil current, the difference in the voltage at point p when t 2 is conducting and at point p when t 1 is conducting creates hysteresis in the detection capability of schmitt circuit, and care must be taken in setting the values. How reed relays work the item reed relay covers dry reed relays and mercurywetted contact relays, all of which use hermetically sealed reed switches. They are made up of electronics components like thyristors and are controlled with triggering. A relay is an electrical switch that uses an electromagnet to move the switch from the off to on position instead of a person moving the switch.
Now we look at various types of relays which are more popularly used in many applications. These classifications include electromagnetic, solid state, high voltage, thermal relays, and so on. All the relays respond to one or more electrical quantities like voltage or current such that they open or close the contacts or circuits. Types of relays the relay may be defined as an electrical device interposed between the main circuit and the circuit breaker in such a manner that any abnormality in the circuit acts on the relay, which in turn if the fault is dangerous then it causes the circuit breaker to isolate and so to remove the faulty element. Unit i introduction of relays a relay comprises of an. A latching relay, however, is used to control large currents with smaller ones, using a. Control relays are an extremely important electrical part, and they play a vital role in todays electronic devices.
There are different types of relays like reed relay, contactor, buchholz relay, overload protection relay, solid state relay etc. The following groupings will be used in this technical guide. Attraction armature type relay is the most simple both in construction as well as in its working principle. Relays are classified into several types based on their functionality and application they are implemented for. A relay is classified into many types, a standard and generally used relay is made up of electromagnets which in general used as a switch. Solid state relays are relays with no moving parts. The relay is the device that open or closes the contacts to cause the operation of the other electric control. A relay is an electromagnetic switch that is used to turn on and turn off a circuit by a low power signal, or where several circuits. The function of relay is to control the switching of a relatively heavier load which demands high voltages like 240 v ac mains or high current, from a relatively low voltage control signal like. In fact, electronic puls es actually perform the switching.
Applications of relays in electronic circuits automation. Most relays work by energizing a small electromagnet which causes the contacts of a switch to close, as shown below. Semiconductor elements transmit and cut the signal or power and contacts are used to supply the power for the relay. A calculus is developed for manipulating these equations by simple mathematical processes, most of which are similar to ordinary algebra1c algorisms.
Both accomplish the same result but the physical structure and functionality makes them different. These classifications include electromagnetic, solid. Here you can see a variety of relays in small to large sizes. In most designs of machine tool relays, for example, a no contact can generally be replaced in. Protective relaying senses the abnormal condition in a part of power system and gives an alarm or isolates that part from healthy system. Relays are simple switches which are operated both electrically and mechanically.
Coil voltage coil resistance number of switch poles. What is relay and different types of relays pdf elprocus. Also, relays are the best way for galvanic insulation between high and low voltage portions of a circuit. They are made up of electronics components like thyristors and are. The high end applications of relays require high power to be driven by electric motors and so on. Industrial control relays type x steven engineering. Types of relays there are different ways to classify relays. All the relays react to voltage or current with the end goal that they open or close the contacts or circuits. Types and revolution of electrical relays introduction. Relays are electrically actuated devices that act as switches. A 10 or 12 pole relay can be built by adding a second deck. These relays are also called as directional relays.
Show examples of relays garnered from the school auto shop, hvac shop and others. By doug wifb hat could be more ordinary than a switch. Here, passing a small current through the coil causes the iron core to become magnetized. Relays without contacts are not included in this technical guide. A relay is a switching device as it works to isolate or change the state of an electric circuit from one state to another. Basically, relays are of two types either electromechanical or solid state relays. Electromagnetic relay working types of electromagnetic. A control relay is, in essence, a switch that is controlled by electrical current. In electromechanical relays contacts are open or closed by a magnetic force. Relays are a remote control electrical switch that can be switched using low current to control a high current load. It can be expanded to 6 or 8 poles by installing an adder deck. The common emitter resistor r e must have a value sufficiently small compared with the resistance of the relay coil 2.
Unlike cube relays, machine tool relays very often have fieldreplaceable contacts as well as replaceable coils. Thats better, its not really a schematic but it helps, have a look at your board theres already a diode near each relay and id bet my house u1 to u8 are optocouplers, so you get a very good protection. Types of electrical protection relays or protective relays. The working principle of the solid static relays is similar to that of the electromechanical. Lets examine mechanical switching devices and become acquainted with how they look and perform. The new 820 series time delay relays are din rail mountable products offering 10 different timing functions, 2 status leds, ultrawide timing range 0.
Fsrrm24 remote relay module installation sheet description the fsrrm24 provides five form c relays that you can configure as common relays, zone relays, or as programmable relays to use with fseries fire alarm control panels. A relay is a switch that is turned on or off using. The three smaller relays on the bottom row are called signal relays, meaning their contacts are rated for less than 2 amps of. Different types of relays and their working principles relays are the primary protection as well as switching devices in most of the control processes or equipments. Identify as much information as you can about your relays prior to discussion. Two types of vector multiplications have been defined, the scalar product and the. A control relay is an electrical component that opens or closes a switch in order to allow current to flow through a conducting coil, with the. In addition, you can configure the relays as dry contact relays or as 24 vdc output relays. Also, the design, construction, working, applications, and also relay selection is explained in detail. Numerical relays perform many more functions than earlier generations of relays so testing them is more complex. Relays are very powerful devices in the fact they can be used in virtually every industry. Technical explanation for generalpurpose relays omron. When the relay s coil receives sufficient voltage, its relay contact switch closes, turning the device connected to it on. A control relay is an electrical component that opens or closes a switch in order to allow current to.
Most of the relays in service on the electric power system today are of the electromechanical type. In describing some of the complicated types of relays for example, electronic relays. Dictionary says that relay means the act of passing something from one thing to another, the same meaning can be applied to this device because the signal received from one side of the device controls the. Relays require no human interaction in order for the switching to occur. In both types, the reeds thin, flat blades serve multiple functions. Site commissioning is usually restricted to running the inbuilt software selfcheck, verifying that currents and voltages measured by the relay are correct, and exercising a subset of the protection functions. Types of relays there are different types of relays including electromagnetic relays, latching relays, electronic relays, nonlatching relays, multidimensional relays and thermal relays which are classified based on the function, application type, configuration or structural features, etc. Aug 31, 2018 attraction armature type relay is the most simple both in construction as well as in its working principle. Relays were invented in 1835 by american electromagnetism pioneer joseph henry, in a demonstration at the college of new jersey. Relays they are a kind of switch, like those we use everyday in our home and offices to turn on and off electrical devices like bulbs, tvs, fans etc. Types of relay, terminals of relay, application of relay, control input or coil terminals, com or common terminal, no terminal, nc. They work on the following two main operating principles.
Assessment a ask students to draw and label the parts of a relay b ask students to wire up a small relay using a battery and leds lesson extension activities using the internet find examples of the use of relays in appliances, automobiles ad other equipment. Different types of relays, their construction, operation. When the voltage is shut off, the relay s switch opens, turning the device connected to it off. Types of relaysoverload protection relay,solid state. A relay is a simple electromechanical switch made up of an electromagnet and a set of contacts. Relays were used for control of automated systems for machine tools and production lines. Hybrid relays are a combination of the best of both relays with contacts and relays without contacts. Types of relays and relay driver circuit buchholz relay. Machine tool relays differ in appearance and construction from cube relays. A relay is a switch that is turned on or off using electricity. Relays respond to one or more electrical quantities like voltage or current such that they open or close the contacts or circuits. That means they are not magnets unless we power them. Nonpolarized relays nonpolarized relays do not use a permanent magnet in their. Latching relays are electronic parts that are used to control large flow of electrical current with smaller flow of current.
In this article, we will look at how relays work and a few of their applications. In this article, the basics of a relay like energized relay and deenergized relay are explained in detail. Why would these statistics matter to us, when working with relay circuits. In later model cars, manufacturers have started combining relay panels into the fuse box to. A relay is used to control the air conditioner in your home.
Protective relaying is a team work of ct, pt, protective relays, time delay relays, trip circuits, circuit breakers etc. It takes a relatively small amount of power to turn on a relay but the relay can control something that draws much more power. There are also other operating principles for its working. Relays are essential for automation systems and for controlling loads.
Relays are quite common in home appliances where there is an electronic control turning on something like a motor or a light. We will now examine in general terms the functional operating principles of relays and certain of their design aspects. Early electromechanical computers such as the arra, harvard mark ii, zuse z2, and zuse z3 used relays for logic and working registers. Understanding relays page 4 autoshop, all rights reserved. The size of a iso micro relay is a 1 x 1 x 12 square 12 as thick as a mini relay. These contacts in turns close and complete the circuit breaker trip coil circuit hence make the circuit breaker tripped for disconnecting the faulty portion of the electrical circuit from rest of the healthy circuit. Protective relays work in concert with sensing and control devices to accomplish their function. The essentials of numerical relays, their features and. Electromagnets are special type of magnet that are activated only on the application of electricity. Monitoring relays monitor a system conditions such as direction of power and accordingly generates an alarm. In most designs of machine tool relays, for example, a no contact can generally be replaced in the field with a nc contact and viceversa. The same adder deck is used for both the middle and. The outstanding performance of our relays is the result of careful design considerations and our complete commitment to quality.
Depending on the operating principle and structural features, relays are of different types. Under normal power system operation, a protective relay remains idle and serves no active function. It detects the intolerable or undesirable condition with an assigned area and gives the commands to the circuit breaker to disconnect the affected area. Most relays are encased in a plastic or metal housing to keep the moving parts free from outside interference and dust see figure 21. Relays allow a lowpower signal to control a large amount of power. The switching mechanism is carried out with the help of the electromagnet. Contactors and relays contactor relays eaton wiring manual 0611 53 55 the system and the standard european standard en 50011 terminal markings, distinctive numbers and reference letters for certain contactor relays has a direct bearing on the use and application of the modular system. They are also common in cars, where the 12v supply voltage means that just about everything needs a large amount of current.
Therefore, this document is intended to describe about a few basic types of relays that are popularly used in typical loadcontrol. The ladder programming language is often used for designing relay logic networks. Relays consist of a nelectromagnet and also a set of contacts. These types of electromagnetic relays can be utilized as either magnitude relay or ratio relay. Electromagnetic relay working types of electromagnetic relays. Relay operation all relays operate using the same basic principle. The working principle of the solid static relays is. A relay is automatic device which senses an abnormal condition of electrical circuit and closes its contacts. Working of relayshow relay works,basics,design,construction. These relays are employed as auxiliary relay, control relay, over current, under current, over voltage, under voltage and impedance measuring. Relays are typically used when small continuous electrical currents must be used. Types of electromagnets relays are classified into the following types, depending on whether or not they have a permanent magnet. In fact, some of the first computers ever built used relays to implement boolean gates. As the name indicates, these relays have contacts and use an electromagnetic operation to mechanically open and.