Everything You Need to Know About Magnetic Contactor

Have you ever worked with a magnetic contactor? Hein Moeller was the first to create it, and it has been utilized in switching applications for many years. The magnetic contactor remains the essential component of the controlling applications due to its massive market size. Based on my investigation, I’ll explain all of this device’s technical details in this article. But, first and foremost, what are contactors, and how do they function?

What Are Contactors?

A contactor is a low-voltage circuit component that switches a higher-current electrical power circuit. It is similar to a relay in that it is electrically operated (more than 15 amps or a few kw). It contains rapid open and close capabilities that control and suppress the electrical arc discharged when a powerful motor current is stopped, allowing it to be connected directly to devices with a high load. However, it is not intended to act as a circuit breaker in the event of a short circuit.

Contactors are available in various shapes and sizes, with capacities ranging from a low breaking current load to extremely high amperage and voltage. Sizes range from a few centimeters to almost a meter in diameter, with various features depending on the use. Almost all standard contactors contain many type A or ‘usually open’ connections, and some incorporate low-current auxiliary contacts for independent operations like pilot lights.

The enclosure, the electromagnet or Coil, and the contacts are the three parts of a contactor (sometimes also called poles). The Coil and contacts and any auxiliary contacts are housed in the enclosure, which is self-explanatory. It’s made of any insulating material to insulate and safeguard the contacts, such as thermosetting plastic.

It protects against environmental contaminants such as oil, dust, and weather by preventing individuals from touching the contacts. The Coil, also known as an electromagnet, comprises a static core and a moving score that provides the driving force that closes the contacts. The current-carrying components are the contacts, which might comprise power and auxiliary contacts as well as contact springs.

A magnetic field is created when a current is passed through the Coil, attracting the contactor’s moving core. This moving core uses electromagnetic force to move the moving contact towards the fixed contacts, keeping them close together. When the Coil’s power is shut off, the moving core is returned to its original position by a contact spring or gravity, and the contacts reopen.

What Is Magnetic Contactor?

Electrical relays utilized in various electric motors are the same as magnetic contactors. Magnetic contactors are used in electric motors to balance the change in frequency or state of the motor, which is referred to as the motor transitioning from ON to OFF state. The changing parameters of the power sources, which are direct, and the high load of electrical motors cause the frequency of the motor to change.

Magnetic contactors protect the power source and the motor by safeguarding. Magnetic contactors are commonly mistaken for circuit breakers because of their design; however, their operation differs from circuit breakers.

The connection between the motor and the power supply is switched off when the circuit is short of protecting the appliance. The magnetic contactors may be removed from the motors, allowing easy motor work. The likelihood of live current passing to the motor is lowered to 0% when the magnetic contactor is removed.

At the industrial level, relays and magnetic contactors are thought to be the same thing, yet they have a lot of variances. For loads up to or less than 10A, a relay is utilized, while for loads larger than 10A, a magnetic contactor is used. Single-phase appliances normally employ relays, but three-phase appliances often use a magnetic contactor. The connection to the appliance on a relay is by a common contact, but the connection to an appliance on a magnetic contactor is via two poles

The Magnetic Contactor’s Main Structure

Magnetic contactors are made up of the following fundamental components.

The Iron Core

There are two sections to the iron core:

Fixed Core

When the Coil Is Activated, It Transforms into An Electromagnet.

Moving Core

A Magnetic Contactor Closes When the Coil Is Powered, Causing the Moving Core to Glide into The Fixed Core.

Coil

The Coil is powered to close the main contacts, and the power of that Coil is used to control the auxiliary contacts.

Contact

There are mostly two varieties to choose from.

Main Contact

The main contact, often known as “the main Contact,” links the electrical system to the load in the power circuit.

The primary contacts are built for hundreds of ampacity or more, while the auxiliary connections are meant for tens of ampacity or less.

Auxiliary Contact

Auxiliary Contact is a second switching device with the “auxiliary contact control circuit.” Normally open (NO) or normally closed (NC) connections are available (NC). When a contactor is de-energized, it is generally open, and when it is energized, it is normally closed.

Auxiliary contacts can pass tiny currents and indicate the state of the main contacts. In other words, it serves as a link between the control system and the user.

Types of Magnetic Contactors

Magnetic contactors are primarily classified into two types.

AC Contactor

Contactors for AC electricity are classified into four types based on the nature of the load and how they are used:

AC 1 Magnetic Contactor

This type of contactor is useful in resistive loads like heaters and electric furnaces and non-inductive or mildly inductive loads with a power factor of 0.95 to 0.99.

AC 2 Magnetic Contactor

For starting slip-ring motors. As a slip ring motor, it’s appropriate for retractable loads. They favor applications with a lot of torque current.

AC3 Magnetic Contactor

Up to the speed of a squirrel cage motor, it is suitable for starting and stopping loads. This sort of contactor can endure a high current for an extended time. Elevators and lifts are two examples.

AC4 Magnetic Contactor

Suitable for running the motor circuit and reversing the squirrel-cage motor spin regularly. It’s also employed in rapid start/stop situations. Example-Cranes.

DC Contactor

DC contactors are classified as follows.

DC-1 Magnetic Contactor

Inductive and somewhat non-inductive loads, resistance furnaces, and heaters are possible applications.

DC-2 Magnetic Contactor

Suitable for plugging, inching, Shunt motors, starting, dynamic breaking

DC-5 Magnetic Contactor

Suitable for dynamic braking, Series-motors, starting, plugging, inching.

Advantages of Magnetic Contactors

There are several advantages to using relays and magnetic contactors compared to alternative switches.

Provides operators with a high level of safety.

Provide ease of control

Economical compared to manual controls

It’s possible to control it with an automatic device or via a remote control.

Applications of Magnetic Contactors

Magnetic contactors have a variety of uses. Here are a few examples.

Magnetic Motor Starter

Motor overload protection is provided by an electrically driven switch (contactor). Magnetic motor starters are similar to contactors, but they also feature a built-in overload. Heaters or electrical overloads detect excessive current flow to the motor in overloads. A magnetic contactor and an overload relay make up the magnetic motor starter.

Lighting Control Contactor

It is utilized for remote or local switching of relatively big mercury, fluorescent, or tungsten lamps and centralized ON/OFF control of LED lighting loads.

Working Principle of Magnetic Contactor and Contact Point NO/NC

When voltage is applied to a coil inside a Magnetic Contactor, the Coil becomes a magnet, and the magnet pulls the switch pole (Contact Point) on the Magnetic Contactor, causing the pole that was previously not connected (disconnected) to become connected and poles that were previously connected to become disconnected.

As a result, we can conclude that a Magnetic Contactor is an Electrical Device that requires an Electric Voltage to function. The Poles in it can be disconnected or connected.

There are two different contact points on a magnetic contactor: NO and NC.

The purpose of a Magnetic Contactor is to connect or disconnect an electric circuit. A Magnetic Contactor has two types of Contact Points:

NO (Normally Open)

Normally Open (NO) is a term used to describe a situation in which the This Pole is not connected (Open) when a Magnetic Contactor is not provided an electric voltage (Normal state); nevertheless, when the magnetic contactor’s Coil is supplied, a voltage, this Pole will be connected (closed).

NC (Normally closed)

When a Magnetic Contactor is not provided an electric voltage (Normal state), this Pole is connected (Closed), and when the magnetic contactor’s Coil is supplied electricity, this Pole is broken (open) or not connected.

Contact Points of NO and NC can be found on TIMER, RELAY, Thermal Overload Relay, Push Button, Controller, Electric Sensor, and other electrical components, in addition to Magnetic Contactors.

Magnetic Contactor Parts

There are three basic parts/components in a magnetic contactor. The contacts carry the electricity through the magnetic contactor. Power contacts, contact springs, and auxiliary contacts are all included in the contact. The magnetic contactor’s circuit is encased in an insulating substance such as Nylon 6, thermosetting polymers, or Bakelite. If the circuit is touched, it is encased.

In the event of a magnetic blowout, the blowout coils move the electric arc, which is the main element of the contactor. Economizer circuits are occasionally inserted in the circuit of the magnetic contactor as an extra circuit. This economizer reduces the coil current in the closed state by lowering the magnetic contactor’s power requirements. Economizers are typically found in the coils of dc contactors and huge ac contactor coils.

Magnetic Contactor Functions

When the electricity in the magnetic contractor starts flowing, the electromagnet in the magnetic contractor generates a magnetic field. The magnetic field created is a strong magnetic field that draws the magnetic contractor’s iron core into the Coil, causing an electric arc to form.

This is how the power gets to the magnetic contractor. The magnetic contractor is taken away from the attached gadget to stop working. The connection between the core and the Coil is also removed when there is no electrical current in the magnetic contractor and the circuit connection is broken.

How Do You Wire A Magnetic Contactor?

Before connecting the product, make sure the label values are appropriate for the system you’ll connect to. After that, look for the A1 and A2 terminals. Coil terminals are the type of terminals used here. When the Coil is electrified, the contractor’s main power contacts are closed. Connect A1 to phase (+) and A2 to neutral (-).

Then connect the main power connectors to L1, L2, and L3. Auxiliary contact inputs are also defined as NO and NC. Auxiliary contacts send position information from the contactor to remote devices, such as open-close information.

Tightening the product’s screws should be done following the torque values printed on the product. If you exert too much power on the screws, they may become worn, resulting in an electrical spark when they are energized.

Problems Related to Magnetic Contactor

If magnetic contactors are chosen correctly and utilized under normal conditions, they will not fail. Contact wear and coil burn are the two most common issues.

When a large amount of current is transmitted via the power contacts, they become heated and cling together. Unlike a circuit breaker, a magnetic contactor is not a protective device. When an overcurrent is passed through a circuit breaker, it causes it to trip. However, overcurrent flowing through the magnetic contactors causes the primary contacts to stick.

The Coil will also burn if the voltage provided to the coil terminal is not nominal. As a result, the power contacts and Coil must provide nominal voltage and current values. For improved system protection, protection devices such as overload relays and fuses must be utilized with the contactor.

Conclusion

The magnetic contactor isn’t a safety device. Like a circuit breaker, it does not protect a circuit in any condition. Switching is the function of a magnetic contactor in a circuit. This switching could be linked to high power handling, frequent operations, and other factors.

We can control any motor from a distance using a magnetic contactor. Magnetic contactors in the kilo ampere range are available on the market. We hope you found this information to be useful.

Lastly, if you are looking for magnetic contactors to purchase or any other electrical component, contact us at ICRFQ, we are the best electrical manufacturers in China.