Contactors & Auxiliary Contacts

The RS range of contactors and auxiliary contacts provides the solutions you need for heavy-duty electrical applications for industrial-grade machinery. Used in everything from lighting and furnace heating control to automation machinery and materials handling with varying voltage rating, a high-quality range of contactors is essential for voltage control. RS supplies contactors and auxiliary contacts from trusted brands such as SIEMENS, Schneider Electric, ABB, Eaton, Allen Bradley and our own RS PRO range.

How Contactors Work

Contactors are electromagnetic switches designed for high-current applications. Much like relays, which are used for switching smaller electrical loads, contactors operate based on the principle of electromagnetism.

A coil within the contactor is energized, creating a magnetic field that attracts a movable armature. This armature is connected to a set of contacts, typically in a normally open (NO) configuration. When the coil is energized, the armature closes the contacts, completing the electrical circuit and allowing current to flow.

Unlike power relays, which are typically used for smaller electrical loads, contactors are designed to handle larger currents. This makes contactors ideal for control of voltage distribution to motors such as AC electric motors, lighting systems, or heating elements, as these applications involve high currents.

Types of Contactors

Contactors come in various types, primarily categorized by their coil voltage and compatibility with AC or DC power sources. AC coil contactors are the most common, designed to operate with alternating current. They are available in different voltage ratings, including 120v coil contactors and 240v coil contactors, which are widely used in residential and industrial settings.

For DC applications, DC coil contactors are employed. These contactors are specifically designed for direct current circuits and can be found in various voltage ratings such as 12v or 24v coil contactors, often used in automotive or battery-powered systems.

Additionally, there are dual coil contactors, which can operate with either AC or DC power sources. This versatility makes them suitable for applications where the power source may vary or where both AC and DC circuits need to be controlled.

Advantages of AC Coil Contactors

AC coil contactors offer several advantages. They are generally more readily available and less expensive than their DC counterparts. AC coils also tend to consume less power, making them more energy-efficient. Furthermore, AC coil contactors are less prone to coil burnout due to the nature of alternating current.

Selecting the Right Contactor for You

When choosing a contactor, several factors must be considered as follows:

AC Number: This refers to the number of phases the contactor is designed to handle. Common options include single-phase and three-phase contactors. Single-phase contactors are suitable for applications with a single AC power source, while three-phase contactors are used for systems with three alternating currents. Ensuring the contactor's phase compatibility with the power supply is crucial to prevent damage and ensure proper operation.
Coil Voltage: The coil voltage is the voltage required to energize the contactor's coil, which activates the switching mechanism. AC and DC Contactors are available with various coil voltages, such as 24V, 120V, or 240V. Selecting the correct coil voltage ensures that the contactor is compatible with the control circuit's voltage level.
Power Rating: The power rating of a contactor indicates the maximum current and voltage it can handle safely. It is crucial to choose a contactor with a power rating that exceeds the expected load requirements of the application. Overloading a contactor can lead to overheating and potential failure.
Certification and Industrial Standards: Reputable manufacturers ensure their contactors meet relevant industrial standards, such as IEC standards. These standards define safety, performance, and testing requirements for contactors. Choosing certified contactors guarantees compliance with industry regulations and ensures reliable operation in demanding environments.
Environmental Considerations: Contactors may be exposed to various environmental conditions, such as temperature extremes, humidity, or dust. It is essential to consider the operating environment when selecting a contactor. Some contactors are designed for specific environments, such as harsh industrial settings or outdoor installations. Additionally, the AC frequency, typically 50Hz or 60Hz, should match the local power grid frequency for optimal performance.

Role of Auxiliary Contacts

Auxiliary contacts play a crucial role in high-voltage systems, working alongside coil contactors to enhance functionality and control. As internal components of contactors, these smaller contacts manage lower power signals, allowing for the coordination of various electrical functions within a complex system. While contactors handle the main power switching for high-voltage applications, auxiliary contacts are utilized for tasks like signaling, interlocking, and controlling additional circuits.

For instance, in a high-voltage motor starter, auxiliary contacts might be used to signal when the motor has started, enabling other parts of the system to respond accordingly. They can also be used to create interlocking mechanisms, ensuring that certain operations occur in a specific sequence or preventing incompatible actions from happening simultaneously. This level of control and coordination is essential in complex power control systems, where safety and reliability are paramount.

Applications of Contactors and Auxiliary Contacts

Contactors and auxiliary contacts find widespread applications across various industries as listed below:

Automotive Industry: Contactors of different voltage ratings are employed in electric vehicles (EVs) to control the flow of high currents from the battery to the motor. Auxiliary contacts might be used to monitor battery levels or manage charging processes.
Manufacturing: In industrial settings, contactors play a vital role in controlling the power supply to motors that drive conveyor belts, robotic arms, and other machinery. Auxiliary contacts can be utilized to monitor the status of these motors or create safety interlocks.
Marine and Offshore: On ships and offshore platforms, contactors are used to manage power distribution systems, ensuring the reliable operation of essential equipment. Auxiliary contacts may be used to control lighting circuits or activate alarms in case of malfunctions.
Energy Sector: In power plants and substations, high-voltage coil contactors are employed to switch large electrical loads, such as transformers and generators. Auxiliary contacts can be used to monitor the status of these high-voltage systems and provide feedback to control systems.
Food and Beverage Industry: Contactors are used to control industrial ovens, refrigeration systems, and other equipment in food processing plants. Auxiliary contacts might be used to monitor temperatures, ensure proper sequencing of operations, or activate safety shutdowns.

Purchasing Contactors and Auxiliary Contacts from RS

RS offers a comprehensive selection of contactors and auxiliary contacts for power control needs, catering to diverse voltage requirements. With a focus on quality assurance, you can trust the reliability and performance of our products. Our team of experts is readily available to assist you in choosing the right components for your specific application, ensuring optimal compatibility and functionality.

Explore our extensive range of contactors and auxiliary contacts today to find the perfect solution for your power control requirements. For more details on our delivery options and charges, please check our delivery information.