Some of the advantages of contactor are as follows:
- It has a simple operating principle.
- It has a high load capacity.
- Its construction is not complex.
- It is available for different ratings.
- It is compact in size. (Especially mini contactors)
- It is cost-friendly. (Check price)
- It does not require so much maintenance.
- It can operate at very low and high temperatures.
What's the "definite purpose" of a contactor?
A contactor is a special type of relay used for switching an electrical circuit on or off. They are most commonly used with electric motors and lighting applications. The use of a contactor provides a level of isolation away from the high electric currents associated with those applications, protecting workers and equipment.
What is the difference between a contactor and a motor starter?
Here are those:
- A contactor is an electrically controlled switch similar to a relay. ...
- A contactor applies voltage to a contactor coil to close the contacts and to supply and interrupt power to the circuit. ...
- A contactor is without the overload coupled whereas with a starter we have options for different overloads to be used.
What is the main function of contactor?
Working Principle of Contactors:
- Types of Contactors: How many loads it can bear. ...
- Difference between AC Contactors and DC Contactors: When the AC contactor shuts down, the fire inside it is automatically extinguished. ...
- Advantages of Contactor: Construction is easy. ...
- Disadvantages of Contactor: In the absence of a magnet-filed, the coil may burn. ...
What is the difference between a relay and a contactor?
- The most compact in size and light in weight.
- A large number of contacts with high switching capacity.
- ‘Snap-fit’ arrangement of various parts.
- ‘Push-on’ type contacts for quick modification/replacement at the site.
- Very high endurance for the high frequency of operations.
What are the application of contactors?
The most common application of contactor is in the starter that used to turn ON and OFF the equipment like motor, transformer, etc. A contactor is an electrically controlled switch used for switching a power circuit, similar to a relay except with higher current ratings.
What is the reason for using contactors and relays?
Relays are used to control contacts of an electrical circuit due to a change of parameters or conditions in the same circuit or any other associated circuit. Contactors, on the other hand, are used to interrupt or establish connections in an electrical circuit repeatedly under different conditions.
What is the advantage of using a contactor in a motor circuit?
It does not require so much maintenance. It can operate at very low and high temperatures. It has wide application areas such as motors, heaters, lighting, etc. It has various types such as power, mini, capacitor, modular, and bar type.
What do contactors control?
0:234:46What is a Contactor ? How does it work ? And how to choose a correct ...YouTubeStart of suggested clipEnd of suggested clipContactors are used to make and break power supply lines running to a load. Or to repeatedlyMoreContactors are used to make and break power supply lines running to a load. Or to repeatedly establish and interrupt an electrical power circuit contactors are used starting with light loads to the
Which is better relay or contactor?
For switching low power, when the additional safety features of a contactor are not necessary, a relay is typically the more economical choice.
What is the difference between a breaker and a contactor?
An electronic contactor is a simple switching device, whereas the circuit breaker is a protective system. The primary function of a contactor is controlling the power. A circuit breaker does the protecting. Contactor works under normal situations.
Do I need a contactor?
While both are electrically operated switches employed for control and switching of loads, contactors are better suited to handle 10A or above, while relays are happiest operating below 10 amps....Contactor vs. Relay – the Differences.RelaysContactorsRelatively smaller in sizeLarger when compared to relays3 more rows•Aug 29, 2019
What is a disadvantage associated with the use of contactors?
In the absence of a magnetic field, the coil may burn. Aging of components causes corrosion of materials when exposed to moister.
What is the difference between a magnetic starter and a contactor?
A contactor applies voltage to a contactor coil to close the contacts and to supply and interrupt power to the circuit. On the other hand, a starter employs overload relays to protect the motor from load surges by shutting it down to prevent overheating.
How many circuits can a contactor control?
Contactors can be of the three pole type, with a high ampere rating and turn on and off a large load, or an entire panel by switching the feeder on and off. Lighting contactors can also be of the multi-pole type, rated to make and break many 20/30/40 amp branch circuit loads (generally 4 – 20 circuits).
How do you use a contactor as a switch?
1:024:54How to Make a Remote On and Off Switch with a Contactor - YouTubeYouTubeStart of suggested clipEnd of suggested clipContact. I will be using two wires one of the wires will go to the opposite side of the normallyMoreContact. I will be using two wires one of the wires will go to the opposite side of the normally open push button and the other wire will go to one side of the normally closed push-button.
What are the two basic types of contactors?
There are different types of contacts in a contactor, and they are; auxiliary contact, power contact, and contact spring. The power contact has two types that are; stationary and movable contact.
What is the purpose of a relay?
Relays are the switches which aim at closing and opening the circuits electronically as well as electromechanically. It controls the opening and closing of the circuit contacts of an electronic circuit.
What is the main difference between a relay and a contactor and between a contactor and a magnetic motor starter?
Comparison of Relay and ContactorsRelaysContactorRelays 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.Relatively smaller in sizeLarger when compared to Relays5 more rows
What is the difference between control relays and contactors?
Control Relay is more commonly used in control circuits which are single phase circuits. Contactors are typically built for switching 3-phase load. A Contactor consists of a minimum one set of three phase power contacts and in some cases additional in built auxiliary contacts are also provided.
What are the three major parts of a contactor or relay?
A contactor consists of three basic parts: the operating coil, the associated magnetic circuit and the contacts that are actuated by the coil.
What is AC1 in industrial automation?
A contactor is a switching device, having one stable position, operated otherwise than by hand. It is an important building block in industrial automation. A contactor can be operated by electrical, pneumatic or electro-pneumatic means.
What is contactor relay?
A contactor is another name for relay, usually used for large high power relays for starting motors. A small signal like 24V can control the relay coils to close the main contacts that carry tens or even hundreds of amps and 240 VAC or higher. 3.8K views. ·.
How does a magnetic coil work?
It operates with a signal received from a push button or from an electronic remote controller, or within the logic circuit signal. It consists of an electro magnetic coil of certain voltages, as per the design and circuitary requirements and gets on /off, whenever the magnetic coil receives voltage.
What are the parts of a relay?
A relay has two main parts: a relay coil and relay contacts. The contacts are either normally open or normally closed. when the relay coil is energized it generates a magnetic field that is used to either open or close the contact.
What is an electrical contactor?
Electrical contactor or relay, is like a multiple switch to make the logic contacts of NO /NC, to make open /close to run the electrical /electronic circuits as per the design and requirements for a machine, or any other applications.
What does NC mean on a contactor?
Here NC means normally closed contact and it will open the circuitary path when relay is on. And NO means normally open contact and it will close the circuitary path when relay is on. While ordering a contactor, we have to mention the type of contactor, its make, model and number of NO /NC contacts and the operating voltage ...
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Contactors are almost used in all control panels I see all the time in my work. Starting from small lighting control panels to medium voltage motors control panels. No matter what voltage level the panel is, the contactor plays an essential role. In this article I will provide you 7 important answers you should know. Let’s get started directly.
Why do contactors have thermal ratings?
The maximum amount of rated current of the contactor, when controlling a thermal load (i.e resistive load) is the contactor thermal rating. The thermal rating of the contactor is mentioned because the rating current of the contactor depends on the load type, inductive or resistive.
Difference Between Contactors and Capacitor Contactor?
The power contactors, are the contactors that are used in the circuit to simply switch the circuit on or off, for any load type (inductive or resistive).
How does a vacuum contactor work?
Vacuum contactor, is a contactor which moving and fixed contacts are surrounded by vacuum inside a sealed tube, to prevent the arcing during the switching on and off. This contactor is very suitable to medium voltage applications, in dusty workplace.
What are the uses of vacuum contactors?
In my work we use vacuum contactor in a VSD panel of a medium voltage motor, its operating voltage is 3.3 KV.
What was the first contactor for a knife blade switch?
The knife blade switch contactors were introduced in the late 1800s. It is safe to assume that they were probably the first types of contactors that were used. Their applications were mostly to control electric motors. They consisted of a metal strip which is designed to drop into a contact when operational. The switch was equipped with a lever for pulling it up or pushing it down. Back then, the contactors were so big; one had to stand next to the knife switchblade to level the switch into a closed position. However, as with old technologies, this method of switching was not efficient enough, and there was functional problems that came with it. The main problem was that it made the contacts wear out quickly. It was difficult to manually open or close the switch quick enough to prevent arcing; as a result, the soft copper switches underwent corrosion, this process made them more vulnerable to dirt and moisture which led to rusting. As years passed and technology began to advance, larger motors were developed. The larger the motors, the more currents they require to work. But it is extremely dangerous to operate such high current carrying switches, so these type of contactors were no longer efficient. Even though technology was continuously improving, the knife blade switches could not be fully developed due to the problems and risks of operational hazards and short life of the contacts
What is contactor in motor?
Contactors are compact and can be field mounted easily. Usually, these devices feature multiple contacts. The contacts are mostly normally open, and they provide operating power to the load whenever the contactor coil is powered. Contactors are popularly used with electric motors.
How does a contactor work?
The operating principle of the contactor is quite simple; the current flowing through the contactor energizes the electromagnet. The energized electromagnet then creates a magnetic field. This causes the core of the contactor to move the armature. The circuit is then completed between the fixed and moving contacts by a normally closed (NC) contact allowing the current to pass through the contacts to the load. When the current is stopped from passing through, the coil is de-energized and opens the circuit. The contactors contacts are able to rapidly open and close, which is why they are able to handle larger loads. Since contactors are designed to rapidly open and close contacts, moving contacts may bounce as they rapidly collide with fixed contacts. Bifurcated contacts are used in many contactors to avoid bouncing.
Why are contactors used in high current?
Contactors are most commonly used with high-current load because of their capability to handle current well over 5000 amperes and high power well over 100kW. When heavy motor currents are interrupted, they produce arcs. A contactor can be used to reduce and control these arcs.
Why are contactors so efficient?
These contactors operate electromechanically and do not require human intervention. With their advanced technologies, they can be operated remotely, and this makes them safer and more efficient since they will not required to be operated manually. Only a small amount of current is needed by the magnetic contactor to open and close the circuit, so it is also energy efficient.
What happens when electric current passes through contactor?
When electric current pass through the contactor, it causes the electromagnet to create a strong magnetic field. This magnetic field pulls the armature into the coil, and this creates an electrical arc. Electric currents flow in through one contact and into the device in which the contactor is embedded.
What is contactor in electrical?
Basically, a contactor is an electrical switching device. It is used for switching an electrical circuit on and off. It is a special type of relay, but there is a basic difference between the contactor and a relay. The contactor is mostly used in applications where higher current carrying capacity is involved, while the relays are used ...
What voltage is a contactor?
Common coil voltages are 24V AC and DC coil, and 110V and 230V AC coil options, with many different amp and wattage levels within each individual category. An example of a contactor is a 24V electromagnetic coil used to control a 230V motor switch circuit.
Why is it important to select the correct type and size of contactor for the specific task you need it to do?
Because the range of available contactors is so vast, it is important to select the correct type and size of contactor for the specific task you need it to do. This can be as simple as turning a non-inductive heater on and off, or as complex as the switching of highly inductive loads such as series and shunt motors.
How to loosen contacts holding block?
Use a screwdriver to loosen the screws in the contacts holding block, and carefully insert the input wires into the block, up to the cut edge of the casing. Make sure no loose strands are left out which could cause damage through unintended contact. Once the input wires are inserted into the contacts, carefully tighten the holding screws.
How to select contactor?
Selecting a contactor relies on correctly identifying three key elements, starting with the contacts: 1 the applicable IEC utilisation category (or a comprehensive duty description) 2 how many normally open (NO) or normally closed (NC) contacts there are 3 what the switching input current is in amperes or the power rating 4 what and how much voltage is used, whether AC or DC, 24V, 230V, etc 5 how many auxiliary NO or NC contacts there are, including any time-delayed contacts. Auxiliary contacts may have a different power rating from the main contacts.
How does a moving core work?
This moving core propels the moving contact by electromagnetic force towards the fixed contacts and holds them closed together. When power to the coil is turned off, the moving core is returned to its initial position, either by a contact spring or by gravity, and the contacts reopen.
What type of contacts are used in contactors?
Almost all standard contactors are fitted with several form A or 'normally open' contacts, and some contactors have optional low-current auxiliary contacts, for independent functions such as pilot lights.
What is the IEC?
The International Electrotechnical Commission (IEC) is responsible for setting international standards for all kinds of electrical and technical components, and publishes a list of applicable contactor types. Selecting a contactor relies on correctly identifying three key elements, starting with the contacts:
Why are contactors not infallible?
Contactors are useful in commercial and industrial applications, particularly for controlling large lighting loads and motors. One of their hallmarks is reliability. However, like any other device, they are not infallible. In most cases, the contactor does not simply wear out from normal use. Usually, the reason for contactor failure is ...
Why do coils overheat?
Coils can overheat if operating voltages are too low or too high; if the contacts fail to open or close because of dirt or misalignment; or if they have suffered physical damage or experienced an electrical short. Coil insulation degrades quickly when it gets too hot.
What does infinite resistance mean?
Infinite resistance means the coil is open. A shorted coil will usually register significant resistance, like a good coil. If you happen to have a matching contactor nearby, compare the two coils. The shorted coil will usually have significantly higher or lower resistance than the good one.
Why do contact surfaces overheat?
Contacts will overheat if they transmit too much current, if they do not close quickly and firmly, or if they open too frequently. Any of these situations will cause significant deterioration of the contact surface and the shape of that surface. Erratic operation and failure will be quick.
How long should a contactor last?
Since a contactor should last for years , don't automatically replace one that fails with an identical unit. Instead, take a few moments to see if there is an obvious problem. A contactor really has only two basic parts: the contacts and the coil. The coil energizes the contactor, moving the contacts into position.
What is the standard for selecting contactors?
When selecting contactors, you'll use one of two common standards: NEMA or IEC. Both match a contactor with the job it has to do, but they do so in different ways. The NEMA selection process always results in a choice of a contactor you can use over a broad range of operating conditions.
Is a contactor a normal operation?
When someone uses a lighting contactor in a motor application, that's a misapplication. The same is true when someone uses a "normal operation" motor contactor for motor jogging duty. Contactors have specific designs for specific purposes.
What is an auxiliary contact?
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.
Why are contactors important?
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.
What is the difference between a contactor and a relay?
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. Additionally, contactors are commonly rated for up to 1000V, while relays are usually rated to only 250V.
What is load capacity relay?
Load Capacity. 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. 2.
Why are contactors connected to overloads?
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 10-30seconds. This is to help protect the equipment downstream of the contactor from damage due to current. Overloads are much less common on relays.
What is a relay in electrical engineering?
According to the Institute of Electrical and Electronics Engineers: Relay – “A device by means of which contacts in one circuit are operated by a change in conditions in the same circuit or in one or more associated circuits”. Contactor – “A device for repeatedly establishing and interrupting an electric circuit under normal conditions”.
Why is a contactor the best?
In practice, you should be looking at the function as well. For any circuit where an overload condition could occur, and a failure to de-energize the circuit will create a dangerous condition, then a contactor is likely the best choice because of the additional safety features.
How long can you use AC contactors?
In emergencies, AC contactors can be used instead of AC contactors. However, the action time cannot exceed 2 hours (because the AC coils’ heat dissipation performance is worse than that of DC coils, depending on their structure). If you need to use it for a long time, it is best to connect a resistor with the AC coil series.
What is the difference between AC and DC contactor?
The coil is usually made into a thin and cylindrical shape to maintain the coil’s good heat dissipation. AC contactor uses grid arc extinguishing device; DC contactor uses magnetic arc extinguishing device.
How many times per hour can an AC contactor run?
The AC contactor’s starting current is vast, and its maximum operating frequency is about 600 times per hour. In comparison, the maximum operating frequency of the DC contactor is 1200 times per hour. In emergencies, AC contactors can be used instead of AC contactors.
What happens when an alternating current passes through an electromagnetic coil?
When an alternating current passes through the electromagnetic coil, the coil generates an alternating driving force on the armature. When the alternating current is zero, the coil’s magnetic current and the actuation force on the armature are both in zero states.
What is the iron core of an AC contactor?
The iron core of the AC contactor produces eddy current loss and hysteresis loss. Laminating the iron core with silicon steel plates reduces the eddy current and hysteresis loss by alternating the iron core’s magnetic field to prevent overheating the iron core. Therefore, the iron core of the AC contactor is usually E-shaped.
What is a copper ring?
A copper ring, known as a short-circuit ring, is inserted into the end of the stem to eliminate contact burnout. This short-circuit loop is equivalent to the secondary winding of the transformer. When the coil is connected to an AC power source, the coil will generate a magnetic current and the induced current in the short-circuit loop.
Can a DC contactor be replaced by an AC contactor?
On the contrary, the DC contactor cannot be replaced by an AC contactor. The number of coils distinguishes the difference between an AC contactor and a DC contactor. A DC contactor’s coils are more than the number of coils of the AC contactor.
