Contactor vs relay

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To turn things on and off, we need devices that are switchable by the application of a current or voltage. Electrically, we have transistors and integrated circuits.

Mechanically, we have relays and contactors. The main difference between contactors and relays is the loads that they are meant to handle. Contactors are used for loads that have high voltages, high currents, or both. Contactors are used for devices that pass more than 15 amps or loads of more than 3kW. For lower amounts, ordinary relays are used. In terms of features, a contactor has some than ties in directly with the previous difference.

At very high power loads, it is very possible that currents will arc across contacts while the switch is in transition.

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Arcing can cause major damage to the contact points causing it to fail much earlier than its expected lifetime. Arcing is much less likely to occur at lower voltages where relays are typically used. Another difference between contactors and relays is the amount of power that they consume. Contactors need to switch larger contacts, thus they also have much larger electromagnets that draw significant amounts of power.

The previous difference is very important when you consider that the circuitry used to decide the switching is electronic in nature. These circuits are not capable of supplying the power needed to switch contactors; on the other hand, can be switched by electronic circuits with relative ease.

Because of this, relays are often used as a middleman between the electronic circuit and the contactor. The electronic circuit provides the power to turn the relay on, which in turn switches a larger voltage source needed to turn on a contactor. You just need to look at your intended application. For most cases, relays can do the job without any problem. But for high power applications, using a contactor may be necessary.

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Cite Ben Joan. April 21, Name required. Email required. Please note: comment moderation is enabled and may delay your comment.Relays are switches that open and close circuits electromechanically or electronically.

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Relays are the primary protection as well as switching devices in most of the control processes or equipments. All relays respond to one or more electrical quantities like voltage or current such that they open or close contacts or circuits. Relays can be categorized or classified into different types depending on the function which they are suppose to do. Some of the categories include protective, reclosing, regulating, auxiliary and monitoring relays.

A contactor is an electromechanically controlled switch used for switching an electrical power circuit. A contactor is typically controlled by a circuit which has a much lower power level than the switched circuit, such as a volt coil electromagnet controlling a volt motor switch. Contactors typically have multiple contacts and those contacts are usually but not always normally-open, so that power to the load is shut off when the coil is de-energized.

Large industrial electric motors are usually protected from overcurrent damage through the use of over overload heaters and overload contacts. If the series-connected heaters get too hot from excessive current, the normally-closed overload contact will open, de-energizing the contactor sending power to the motor.

The main difference between the contactor and Relay is that, Contactor is a high power device while Relay is a low power device.

Contactor vs. Relay

Contactors are used in control circuits with both low and high Ampere capacity that is between 15A to A. Relay on the other hand, is used in control circuits with low Ampere capacity, that is, between 10A and 15A.

Contactors are mainly designed for three phase applications whereas; Relays are mainly designed for single phase application. Contactors are usually designed for high voltage applications and because of this; they have some safety features such as spring-loaded contacts.

contactor vs relay

Spring-loaded contact is an application used to prevent internal short circuit of the contactor when it heavily loaded with high voltage current.

Another safety feature present on contactors is Magnetic ARC suppression. ARC suppression is the reduction of sparks formed when current-carrying contacts are separated.

Relays on the other hand, are not fitted with safety features like spring contacts and ARC suppression system. The switching speed of the relays is very much faster when compared to the switching speed of contactors.

In this regard, relays can be operated with electronic signals whereas contactors cannot be operated with electronics signals. Relays have small electromagnets when compared to the relatively large electromagnets of contactors and in this regard, contactors consume more power than relays. Contactors are comparatively high cost devices when compared to relays.

On the other hand, relays are low cost devices when compared to contactors. Contactors are relatively larger in size and heavier when compared to relays that are relatively small and lighter.Posted by K. Gregoric on Feb 10, PM. In this article, we will explain how each of these devices work and discuss some key selection considerations.

Relays come in a host of designs, from solid-state, which has no moving parts and use semiconductors to control the flow of power, to electromagnetic relays, which uses magnets to physically open and close a switch.

A common type of relay you find is a Mini ISO relaya general purpose relay that comes in an industry standard footprint and fits the needs of many electrical applications such as lighting, starting, horn, heating, and cooling. Solenoids are a type of relay engineered to remotely switch a heavier current.

Similar to the smaller electromechanical cube relays, a coil is used to generate a magnetic field when electricity is passed through it, which effectively opens or closes the circuit.

When determining which one of these three switching products is right for your design, consider the form factor. Typically, greater carrying capacity equals bigger size, so carefully note the amount of space available to ensure the device you need will fit. If there is a conflict, it is time to either rethink your design layout or scale back the electrical system.

Look at the Ingress Protection IP rating to determine the specific protection offered. Operating temperature is another critical point. It is important to note that solenoids and contactors are rated for either continuous or intermittent use. The decision to use a relay, solenoid, or contactor largely comes down to the current carrying capacity needed, while also considering how the form factor will fit into your design footprint.

Know that we would never sell or trade your personal info and promise not to spam you either - we know you're far too busy for that. Specialists in DC Power. Distribution for OEMs and. Wired2Serve Blog. Relays vs. Solenoids vs. Contactors: A Comparison Posted by K. Solenoids Solenoids are a type of relay engineered to remotely switch a heavier current.

Continuous vs. Intermittent Ratings It is important to note that solenoids and contactors are rated for either continuous or intermittent use. Choosing a Switching Device The decision to use a relay, solenoid, or contactor largely comes down to the current carrying capacity needed, while also considering how the form factor will fit into your design footprint.

Here are a few top picks:. Subscribe to Email Updates. Subscribe to the Wired2Serve Blog. Recent Posts. All rights reserved.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up.

As known, contactor is used to switch higher capacity than relay. But there some relays can switch high current too, such as, some power relays can switch current beyond A, and there are contactors to switch only A. So, if a relay has a same switching current with a contactor, which one to choose? Wikipedia's Contactor article explains it pretty well. Unlike general-purpose relays, contactors are designed to be directly connected to high-current load devices. Relays tend to be of lower capacity and are usually designed for both normally closed and normally open applications.

Devices switching more than 15 amperes or in circuits rated more than a few kilowatts are usually called contactors. Apart from optional auxiliary low current contacts, contactors are almost exclusively fitted with normally open "form A" contacts. Unlike relays, contactors are designed with features to control and suppress the arc produced when interrupting heavy motor currents. Magnetic suppression and arc dividers are typically utilized when switching multi-horsepower motors.

Magnetic suppression is accomplished by forcing the arc to follow the longer field lines of a fixed magnet placed in close proximity to the contacts. Figure 3 shows a schematic representation of magnetic arc suppression. Look carefully at the application and contact rating - particularly for motor or inductive loads. If you are satisfied that either will suffice you can choose based on some other criteria such as cost.

Generally not. While doing this does reduce the long term heating of the individual contacts due to steady current running through them it is a problem during switching due to timing differences.

Even wiring contacts of the same relay in parallel is risky as they never are perfectly aligned and the first one to make and last one to break carry the full switching action.

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Load voltages maybe? Both contactors and relays can be used for switching high current loads, but contactors can be used for high-voltage applications as well. Besides, contactors do have some protections like overload on-board.

contactor vs relay

About paralleling relays: Can you guarantee to turn on all the relays at the same time? Can you imagine what will happen if one turns on before all the others and remains on even for a short time?

I'm not telling that it will burn or fail, but depends on the relay's contact performance. Just to consider EM contactors are quite close to relays, so I advise to check the specs rather than deciding upfront that you want a contactor.According to the Institute of Electrical and Electronics Engineers :. Both perform the same task of switching a circuit! So What really differentiates the two devices?

Relays are generally classified as carrying loads of 10A or less, while a contactor would be used for loads greater than 10A, but this definition, while simple, gives an incomplete picture. It leaves out any physical differences, or standards. Contactors are almost exclusively designed to operate with normally open Form A contacts. This means that with a contactor, when it is de-energized there is typically no connection.

With a relay there very well could be. To confuse things a bit, contactors are often fitted with auxiliary contacts which can be NO or NC however these are used to perform additional functions related the control of the contactor.

For example, the contactor may transmit power to the motor, while the auxiliary contact is in the control circuit of the motor starter and commonly used to turn on a pilot light indicating the motor is operating.

Because contactors are typically carrying high loads, they often contain additional safety features like spring-loaded contacts to help ensure the circuit is broken when de-energized. This is important because in high load situations contacts can weld themselves together. This can create the dangerous situation of a circuit being energized when it is supposed to be off. Spring-loaded contacts help to reduce this chance, as well as ensure all circuits are broken at the same time.

Since relays are typically for lower power, spring-loaded contacts are much less common.

Contactors vs Relays: What’s the Difference?

Another safety feature commonly included in contactors, due to the high loads they typically carry, is arc suppression. Magnetic arc suppression works by extending the path an arc would have to travel. If this distance is extended further than the energy can overcome, the arc is suppressed.

Lastly, contactors are commonly connected to overloads that will interrupt the circuit if the current exceeds a set threshold for a selected time period, usually seconds. This is to help protect the equipment downstream of the contactor from damage due to current.

Overloads are much less common on relays. Contactors are typically built for and used in 3-phase applications where a relay is more commonly used in single phase applications.

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A contactor joins 2 poles together, without a common circuit between them, while a relay has a common contact that connects to a neutral position.Relays are basically switches which are primarily used for the protection of equipment. It generally uses two circuits — A control circuit and a power circuit.

The control circuit regulates the flow of power and performs the basic switching operation using a small amount of current which can in turn be used to control a circuit with a high amount of current.

Understanding Relay Vs. Contactor : 15 Basic Differences

In small scale applications, fuses and similar devices are used for protection purposes. In large scale industries, where high reliability is required, relays are preferred.

Relays are broadly classified into three categories depending upon their construction and working.

Contactor vs Relay - Difference between Relay and Contactor

The working principle of electromagnetic relays is the electromagnetic action. The fundamental construction aspects of an electromagnetic relay are very simple. It consists of three parts —. Electromagnet — This is a temporary magnet that becomes a magnet only when an electric current is passed through it. An electromagnet is formed by wounding a wire around a soft iron core. Whenever electric current is passed through the wire, a magnetic flux is induced in the iron core which makes it act like a magnet and produce a magnetic field around it.

Movable Armature — This is commonly known as a plunger or a solenoid. It is the movement of this part that opens or closes the mechanical contacts as it is attracted by the magnetic field generated by the coil.

The movable contact moves in response to the magnetic field generated by the electromagnet, thereby making the contact Normally Close NC. The contact breaks open in case there is any fault detected in the system. The figures illustrate the working of an electromechanical relay. The relay is energised by the magnetic field generated due to the electromagnet and thereby changes its contact from Normally Open to Normally close.

Only when the relay contacts are Normally close, the power circuit is completed and the load bulb in this case gets the power. In case of any fault, the contact changes to Normally Open, thereby causing an interruption in the flow of current and ensuring the safety of the equipment. Static relays are those relays which do not contain any moving parts. They are contrasted with electromechanical relay, which has moving parts for switching. Static relays incorporate static components such as solid state devices, magnetic or electric circuits etc.

Static relays utilize high reliability operational amplifiers Op-Amp for the realisation of its basic components. Due to the absence of moving parts, static relays offer many advantages over the conventional electromagnetic relays. Some of them are —. These relays are usually microprocessor based and are programmable according to the needs of the user.

They are more user friendly and offer multi-functional protection schemes. Unlike electromagnetic relays, these do not contain any moving parts and thereby serving all the benefits of static relays as well.

Due to these factors, numerical relays are referred to as present generation relays.

contactor vs relay

One of the major advantages of numerical relays is that it can store pre-fault as well as post-fault data so that it can be used further. Time delay is type of electromechanical relay which are used to provide a delay in the start-up, shut-down or controlling processes.

These relays induce a time delay in making its contact Normally close after the coil has been energized. This is done in order to meet the desired requirements.

These are broadly classified into two types, namely — ON delay time relays and OFF delay time relays. In this type of relays, the timer starts during start-up i. Once the timer reaches the set timing, it stops and the contact closes thereby completing the circuit and turning on the equipment.

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The ON delay time relays involve two types of contacts —. In these types of relays, a delay is introduced during shut down of the equipment.Contactors and relays are two closely related terms leading to confusions and misinterpretations most of the times.

Both of them are electrically operated switches used for control and switching of loads. The basic principle of operation of the contactor and the relay are the same. The difference between them is in term of their application and where they are used.

This article can give you a clear picture of the difference between relays and contactors. Contactors and relays have similar construction.

Both have an external envelope to protect all the internal parts from the external environment. An electromagnetic coil is provided for opening and closing of contacts. The contacts are opened and closed by exciting this electromagnetic coil.

A Contactor is used for switching of motors, capacitors, lights etc, that drains very high current. It has at least a single pair of three-phase input and output contacts. It would be normally open. Some contactors come with additional auxiliary contacts that may be either NO or NC. These auxiliary contacts get activated along with the main contacts. Switching is achieved by energization and De-energization of the contactor coils. Contactors are chosen upon the ampere ratings of the load. Contactors require an additional supply either AC or DC depending upon the type of contactor we use for excitation.

It is used for power switching. A relay consists of at least two contacts and an excitation coil. These contacts may be normally open or normally closed.

These contacts are closed or opened by exciting the coil. Relays are used for switching of control circuits and cannot be used for power switching with relatively higher ampacity. It can be used for switching of small lights, sirens, indication lamps etc.

Relays are switching devices used in any control circuit for checking a condition or multiplying the number of contacts available. Contactors are switching devices used to control power flow to any load. Related Searches: 1. Where are contactors used and where are relays used? Skip to content Sitemap Privacy Policy. Difference between contactors and relays. Relays Contactor Relays are switching devices used in any control circuit for checking a condition or multiplying the number of contacts available.

Relatively smaller in size Larger when compared to Relays Used in circuits with lower ampacity. Max 20A Used in circuits with low and higher ampacity up to A Mainly used in control and automation circuits, protection circuits and for switching small electronic circuits. Used in the switching of motors, capacitors, lights etc. Relays do not have an arc suppression system built-in. Normally, contactors have in- built arc chutes for suppression. Related articles: 1.