Contactors

A contactor is an electromechanical switch designed to manage power flow in electrical circuits, especially those involving high-current applications. Functioning like a relay but capable of handling heavier loads, contactors are essential for activating a variety of systems such as motors, heating equipment, and large electrical loads.

They are particularly useful in providing central control of extensive lighting installations in commercial settings like office buildings or retail complexes. Contactors operate by using a coil that, when energised, either opens or closes the circuit, efficiently controlling power distribution. This can be done independently or as part of a motor starter assembly, ensuring versatile application across various industries.

How Do Contactors Work?

A contactor operates through an electromagnet mechanism. When the contactor's coil is energised, it generates an electromagnetic field. This field exerts a force on the armature—a metallic rod connected to the moving contact—pulling it towards the fixed contact against the force of a spring. This action closes the circuit, allowing electricity to flow through the contactor. The contacts remain closed as long as the coil stays energised.

When the coil is de-energised, the electromagnetic force dissipates. This causes the spring force to retract the armature, separating the contacts and breaking the circuit, returning the system to its off state. This rapid on-off capability is essential for applications requiring frequent and controlled power interruption.

Contactors can be designed to operate with AC, DC, or universal coils. All of which work with both AC and DC currents.

Types of Contactor Specifications and Ratings

There are various types of contactors, and each type will have its own set of specifications depending on your application. Some key specifications are:

Voltage Ratings: AC Contactor or DC Contactor ranging from 12 V to 440 V.

Functionality: Reversing or non-reversing functionality.

Utilisation Categories: Typically categorised under AC3 for motor starting and AC1 for resistive loads.

Pole Configurations: Available from 2 to 10 poles, accommodating different circuit arrangements.

Contact Configurations: Various contact configurations.

Compliance Standards: All contactors adhere to IEC standards, ensuring international compliance and safety.

Magnetic Contactors

Magnetic contactors are the most common type due to their operational efficiency and ability to function without manual intervention. These devices operate electromechanically and can be controlled remotely, enhancing both safety and efficiency. They require minimal current to actuate, making them energy-efficient choices for various applications.

Knife-Blade Switch

Introduced in the late 1800s, knife-blade switches are among the earliest forms of contactors. Originally used to control electric motors, they consist of a metal strip actuated by a lever to make or break contact. While historically significant, their manual operation led to rapid wear and susceptibility to arcing, corrosion, and rust due to the soft copper construction and exposure to environmental elements. As motor technology evolved to require higher currents, the safety and operational efficiency of knife-blade switches diminished, leading to their gradual replacement.

Manual Controller

Developed as a safer alternative to knife-blade switches, manual controllers feature several advancements, including encased units, compact designs, and double-break contacts that interrupt the circuit at two separate points simultaneously. This design allows for safer operation with higher currents in smaller spaces. Although manual controllers offer enhanced safety and efficiency, their requirement for direct manual operation limits their application compared to more modern automated systems.

Difference Between Contactor and Relay

Contactors and relays are both essential components in electrical circuits, but they serve different purposes based on the voltage and current requirements of the application. Contactors are typically used in high voltage applications where the load current exceeds 15A. They are larger in size, making them more suitable for handling higher power applications efficiently. Additionally, contactors are generally easier to maintain and are most often used in circuits requiring normally open (NO) contacts.

Relays, on the other hand, are used for lower voltage applications where the load current is less than 15A. Due to their smaller size, relays are ideal for compact systems and are commonly connected as normally closed (NC) contacts, providing a different type of circuit control. Relays also offer faster switching times compared to contactors, making them more suitable for applications where rapid switching is critical.

Find out more about how contactors and relays have been implemented to enhance train operations in Australia here.

How to Order Contactors From RS?

RS offers a comprehensive range of high-quality electrical contactors from industry-leading brands including Schneider Electric, Siemens, Eaton, ABB, and Allen Bradley. We also stock a selection of accessories used to enhance the function of contactors including, Contactor Overload Relays, auxiliary contacts, mechanical interlocks, and much more.

Business account customers enjoy free delivery on all orders over $40 (excluding GST), with a $10 delivery fee for orders under this amount. On the other hand, delivery is free for orders over $80 (excluding GST) for all private accounts and guest customers; a fee of $12.95 applies to smaller orders.

Delivery Information for Australia

Ensure your order is placed by 5 pm AEST from Monday to Friday to take advantage of next working day delivery for items available locally. Be aware that some regional locations may face longer delivery times, especially for orders requiring special handling such as those containing hazardous materials or oversized packages.

For detailed information on all our delivery services, including special options like same-day delivery and consolidated shipments, please visit our delivery information page. Our streamlined ordering process is designed to help you easily find and receive the right products swiftly and reliably.