Contactors, overloads and manual motor starters carlo gavazzi. From system integrator, oem, engineering consultant and distributor to panel builder and industrial enduser, our. Overload relays are designed to imitate on a much smaller scale the heating patterns of the electric motor it is installed in, and interrupt the current once the heat sensing mechanism in the relay reaches a certain temperature. Relays are classified into several types based on their functionality and application they are implemented for.
The more expensive the electrical gear, the greater the number of relays that will generally be used. When someone uses a lighting contactor in a motor application, thats a misapplication. Fused control circuit transformer and control relay. We teach you the basics of how they work and what they are used. A2 iec contactors relays a2 springer controls company 96074 chester road, yulee, fl 32097 904 2250575 fax. It is crucial to have a good basic understanding of the principles. Typically, students practice by working through lots of sample problems and checking their answers against those provided by the textbook or the instructor. There are various types of contactors, and each type has its own set of features, capabilities, and applications. They both are commonly used in industrial and commercial applications, and function in almost the exact same way.
Electronic overload relays offer reliable and precise protection for motors in the event of overload or phase failure. Contactors and relays contactors dil, overload relays z eaton wiring manual 0611 510 5 5 rated operating current ie a ac3 at 400 v max. However, the basic difference between the relay and contactor is that the contactor is used in applications with higher current carrying capacity, whereas the relay is used for lower current applications. It takes a relatively small amount of power to turn on a relay but the relay can control something that draws much more power. Introduction a contactor is an electrical device which is used for switching an electrical circuit on or off. Build something learning to analyze relay circuits requires much study and practice. Relays lrd43pp are suitable, as standard, for use with lugclamps. Relays respond to one or more electrical quantities like voltage or current such that they open or close the contacts or circuits. The purpose of contactors and relays is to open and close associated contacts. Basic electromagnetic relays basic electricity pdf version. Dec 11, 2017 much like a relay, a contactor is an electrically controlled switch. Fourpole contactors, 25 to 125a in ac1 duty power factor correction contactors, 7. Thats why you need to understand the basics of contactors. Electromechanical relays and contactors this chapter covers representative generalpurpose relays used in the control circuits of most industrial, commercial, and consumer products.
Wired to provide a control sequence, relays may also be used for simple. Contactors are designed mainly for threephase applications. Whatever the application, the function of the contactor is always the same. On the other hand, relays are low cost devices when compared to contactors. Contactors can break current over a wide range of currents, from a few amperes to thousands of amperes, and voltages from 24 vdc to thousands of volts. The basic principle of operation of the contactor and the relay are the same. A relay is used to energize the starter, which, in. The basics of contactors commercial electric products.
In view of the fact that loads with a large inductive compo nent are predominantly used in practice e. It takes a relatively small amount of power to turn. These contactors have a low power consumption for direct control from plc outputs. A contactor can stand on its own as a power control device, or as part of a starter. An overload relay is made up of a heater paired with normallyclosed contacts that open once the heater gets too hot. Contactors are used in applications ranging from the light switch to the most complex, automated. Control and chapterb11 tesys p c rotection omponents from. Contactors are used in applications ranging from the light switch to the most complex, automated industrial equipment. Contactors and relays are two closely related terms leading to confusions and misinterpretations most of the times. In particular, large electrical gear as generators, motors and. However, the basic difference between the relay and. Contactors can be used in control circuits that have both high and low current capacity that is between 9a to 1250a.
A 90340 is a very common, versatile relay that many techs have on their truck so we will use it as the example. Relay operation all relays operate using the same basic principle. Large electric motors can be protected from overcurrent damage through the use of overload heaters and overload contacts. The more expensive the electrical gear, the greater the number of relays that will. Relays are used in control circuits with only low current capacity. The associated contacts have the same identifying letter. Pro tec ted ag ain st polarity reversa l also for ac. They are used in large numbers for the indirect control of motors, valves, clutches and heating equipment.
Each section starts with an overview to introduce you. Each section starts with an overview to introduce you further to the main points about these devices, and the parts that make them up. Much like a relay, a contactor is an electrically controlled switch. In addition to the simplicity which they offer in project engineering, panel building. Contactors are most commonly used for controlling electric motors. Contactors are used by electrical equipment that is frequently turned off and on. Both of them are electrically operated switches used for control and switching of loads. Lrd3pp6 thermal overload relays for use with unbalanced loads class 10 a 1 for connection by screw clamp terminals or lugs.
Aug 10, 2009 relays and contactors can work with high voltage or low voltage circuits and are widely used in all areas of electrical engineering. Eaton magnetic motor starter starters are made from two building blocks, contactors and overload protection. A relay is used to control the air conditioner in your home. For ac relays a distinction is made between synchronously.
The basics of contactors contactors are useful in commercial and industrial applications, particularly for controlling large lighting loads and motors. Control and chapterb11 tesys p c rotection omponents from 0. 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. Thermal overload relays for tesys d contactors class 10 a. A relay is used to energize the starter, which, in turn, switches the motor voltage while the plc controls the relay. Contactors and relays 5 contactor relays contactor relays contactor relays are often used in control and regulating functions. When a relay is used to switch a large amount of electrical power through its contacts, it is designated by a special name. Contactors are used by electrical equipment that is frequently turned off and on opening and closing the circuit, such as lights, heaters, and motors. Relays are used to isolate one voltage level from another. Section title page number introduction to terminal blocks 4.
There are posts on the working of relays, types of relays and so on. Electronic overload relays 3pole contactors and overload. Contactors electromechanical relays electronics textbook. Relays can be used for many different control applications including controlling fans, blowers, other relays or contactors, valves, dampers, pumps and much more. These classifications include electromagnetic, solid state, high voltage, thermal relays, and so on. They both are commonly used in industrial and commercial applications, and. The electronic overload relay can make up a compact starting solution together with contactors. The product offering starts with mini contactors in a compact 12 amp frame size, followed by midi contactors in up to 100 amp frame sizes, and topped off with the power contactors which offer up to 800 amp frame sizes. Ac motor basics ac drive basics chapter 3 ac drives ac drive hardware ac drive operation chapter 4 ac drive applications application considerations application types final exam page 12 if you do not have an understanding of basic electrical concepts, you should complete basics of electricity before attempting.
To assemble fuseless motor feeders you must select combinations of motor protection. A relay is a switching device as it works to isolate or change the state of an electric circuit from one state to another. Relays and contactors use a variety of technologies to switch signals and power connections. Difference between contactors and relays electrical classroom. A contactor is a large relay, usually used to switch current to an electric motor or another highpower load. However, like any other device, they are not infallible. Iec contactors relays a2 springer controls company 96074 chester road, yulee, fl 32097 904 2250575 fax. In most cases, the contactor does not simply wear out from normal use. State the purpose and general principles of control. Terminal blocks, relays and timers this book is divided into three sections.
However, the basic difference between the relay and contactor is that the contactor is used in applications with higher. A plc may be used to control the operation of a mediumvoltage motor, perhaps 2,300v or 4,160v. When a relay is used to switch a large amount of electrical power. From system integrator, oem, engineering consultant and distributor to panel builder and industrial enduser, our comprehensive range of motor starting solutions, products and services delivers the certainty of consistent quality and performance. To complement the contactors, thermal overloads are offered for each frame size, available in several setting ranges. Contactorscontrol relays overload relays pid modules control panel complexity pump fan. Abbs motor protection and control offering is among the widest on the market. Contactors have specific designs for specific purposes.
The product offering starts with minicontactors in a compact 12 amp frame size, followed by midicontactors in up to 100 amp frame sizes, and topped off with the powercontactors which offer up to. Operated application alrt, talrt contactors are mainly used for controlling 3phase motors and more generally for controlling power circuits up to 690 v a. The company offers a wide range of advanced solutions in the field of. Contactors are comparatively high cost devices when compared to relays. Many devices called relays use similar techniques and topologies. However, the basic difference between the relay and contactor. A contactor is an electrical device which is used for switching an electrical circuit on or off. Relays have small electromagnets when compared to the relatively large electromagnets of contactors and in this regard, contactors consume more power than relays. The same is true when someone uses a normal operation motor contactor for motor jogging duty. Jan 25, 2019 relays can be used for many different control applications including controlling fans, blowers, other relays or contactors, valves, dampers, pumps and much more. Upon completion of basics of control components you will be able to. If the seriesconnected heaters get too hot from excessive current, the normallyclosed overload contact will open. The difference between them is in term of their application and. Basic electromagnetic relays worksheet basic electricity.
Main catalogue contactors and contactor relays with ring. However, the basic difference between the relay and contactor is that the contactor is used in. Contactors control the electric current to the motor. Therefore, this document is intended to describe about a few basic types of relays that are popularly used in typical loadcontrol. Oct 01, 2019 contactors can be used in control circuits that have both high and low current capacity that is between 9a to 1250a. Working of relayshow relay works,basics,design,construction. Electromechanical relays and contactors machine design. Relays and contactors can work with high voltage or low voltage circuits and are widely used in all areas of electrical engineering. Overload relays are designed to imitate on a much smaller scale the heating patterns of the electric motor it is installed in, and interrupt the current once the heat sensing mechanism in the relay reaches. An actuating current on a coil operates one or more galvanically separated contacts or load.
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