Auxiliary Contacts

Auxiliary contacts, also known as auxiliary contactors or aux contacts, are electromechanical switching devices used alongside primary switching equipment such as contactors, circuit breakers, switches, and relays. These auxiliary contact blocks are physically linked to the main contacts and operate simultaneously, providing additional control and signalling functions in industrial automation and control systems. Auxiliary contact blocks come in various contact configurations and mounting styles to suit different applications.

How Do Auxiliary Contacts Work?

Auxiliary contacts are affixed to the main contacts of devices like contactors or circuit breakers. When the main contacts open or close, the auxiliary contact blocks change state accordingly, either opening or closing their own circuit. This allows them to transmit status signals to control systems, logic controllers, or other linked devices, enabling remote monitoring, interlocking, and automation.

Auxiliary contacts are available in a variety of mounting styles such as a front mount, snap-on, plug-in, or DIN rail mount and a range of terminal types including screw terminals, screw clamp terminals, and cage clamp terminals making it easy to find the right contact for the application.

What Are Auxiliary Contacts Used For?

Aux contacts serve essential roles in control and safety circuits by providing feedback on the status of main switching devices. Common uses include:

• Signalling and Indication: Activating indicator lamps, alarms, or status displays to show the operational state of equipment.
• Interlocking: Preventing unsafe or undesired operations by ensuring certain conditions are met before a device energises.
• Control Functions: Operating secondary circuits such as pilot lights, auxiliary contact relays, or initiating sequential operations.
• Motor Control: Integrating with motor starters and protection schemes to monitor and control electric motors.
• Circuit Breaker Auxiliary Contacts: Providing feedback and control signals for circuit breakers to enhance protection and monitoring.

Auxiliary contacts can also be used as standalone auxiliary contact switches or integrated into push-button controllers for start/stop functions.

What Are the Different Types of Auxiliary Contact Blocks?

Auxiliary contact blocks typically come in two main types, defined by their default state when the main device is de-energised:

• Normally Open (NO) Contacts: These contacts remain open when idle and close when activated. They are commonly used for switching on devices like status indicator lamps.
• Normally Closed (NC) Contacts: These contacts remain closed when idle and open when activated. NC contacts are often used for interlock functions or to break circuits under fault conditions.

Some auxiliary contact blocks combine NO and NC contacts, mechanically linked to ensure they cannot be closed simultaneously, complying with IEC 60947-5-1 standards for safety and reliability. Choosing between NO or NC contacts depends on your control circuit's specific requirements.

Key Features to Consider When Selecting Auxiliary Contacts

When selecting auxiliary contacts or auxiliary contact blocks for your application, consider these important features:

• Contact Configuration: Choose between NO (Normally Open), NC (Normally Closed), or a combination, depending on the specific requirements of your control circuit.
• Current and Voltage Rating: Match the auxiliary contact’s electrical ratings precisely to your system’s supply voltage and operational current to ensure safe, reliable switching. Durability and Lifespan: Opt for robust, industrial-grade contacts designed to withstand thousands of switching cycles without performance degradation.
• Mounting Style: Select from snap-on, screw-mount, or plug-in styles, ensuring ease of installation and secure attachment to your existing control equipment.
• Contact Material: High-quality materials like silver or gold plating offer superior conductivity, corrosion resistance, and longer service life even in demanding environments.
• Electrical Isolation: Ensure the auxiliary contact provides effective electrical isolation from main contacts to prevent circuit interference and enhance system safety.
• Temperature Rating: Verify that the auxiliary contact’s operating range fits the ambient conditions of your application, especially in extreme industrial settings.

How Auxiliary Contacts Enhance Safety and Monitoring

Auxiliary contacts contribute to system safety, monitoring, and operational control in several key ways:

• Remote Signalling and Indication: Allow operators to monitor equipment status from remote panels or control rooms, improving oversight and operational efficiency.
• Safety Interlocking: Prevent hazardous situations by ensuring that machines or circuits operate only under safe, predefined conditions.
• Fault Detection: Enable early detection of faults or irregularities within the system, supporting faster response and minimising downtime.
• Preventive Maintenance Triggers: Provide real-time alerts for maintenance needs, helping to avoid sudden equipment failures and extend system life.
• Control System Integration: Seamlessly integrate with PLCs, monitoring systems, and alarms for smarter, automated industrial operations.

Choosing the Right Auxiliary Contact for Your Application

Selecting the right auxiliary contact block involves careful consideration of:

• Matching Current and Voltage Ratings: Choose contacts that can safely handle your system’s voltage and current without overheating or failure.
• Selecting the Right Mounting Style: Pick from front-mount, snap-on, plug-in, or DIN rail options to match your panel layout and ease of access.
• Ensuring System Compatibility: Confirm mechanical fitting and electrical signalling compatibility with your existing contactors, relays, and switches.
• Evaluating Environmental Protection: Look for IP-rated contacts that can resist dust, moisture, or other harsh environmental factors.
• Durability and Lifespan: Select contact blocks tested for high mechanical and electrical endurance to guarantee reliable, long-term operation.
• Considering Size Constraints: Ensure that the contact block fits neatly within limited panel space without interfering with other components.
• Checking Temperature Ratings: Validate that the selected contact block can operate within your environment’s expected minimum and maximum temperatures.

Common Industrial Applications of Auxiliary Contact Blocks

Auxiliary contacts and auxiliary contact blocks are critical components in:

• Elevator and Escalator Systems: Used for safety interlocks, position feedback, and operational sequencing to prevent accidents and system faults.
• Packaging and Assembly Lines: Enable precise control of machinery functions, monitor status lights, and ensure smooth, automated workflows.
• Pumps and Water Treatment Systems: Provide reliable monitoring and remote start-stop control to maintain system efficiency and prevent water management issues.
• Oil and Gas: Operate reliably under harsh conditions, ensuring critical safety and operational monitoring in exploration and processing facilities.
• Power Distribution and Electrical Panels: Facilitate automated control, fault indication, and protection features critical to power system management.

Shop Auxiliary Contacts at RS Malaysia

RS is your trusted source for auxiliary contacts in Malaysia. We offer an extensive range of high-quality auxiliary contact blocks from industry-leading brands including Schneider Electric, Siemens, ABB and Lovato.

Besides auxiliary contacts, we also offer a wide selection of tools and components like AC motors, DC motors and manometers — ideal for building and maintaining complete control systems.

Explore our comprehensive range online, and you can count on RS Malaysia for competitive pricing, fast delivery, and expert technical support. For detailed shipping information and service options, visit our Delivery Page.