Auxiliary Contacts Guide: Choosing and Understanding for New Zealand Facilities

1. Mechanical Linkage:

At the heart of auxiliary contacts lies a clever mechanical linkage system. When the primary contacts of a circuit breaker or contactor move, this mechanical linkage comes into play. Think of it like a chain reaction – the movement of the primary contacts triggers the auxiliary contacts to respond accordingly.

2. Status Indication:

Auxiliary contacts are equipped with a set of arms or fingers that move in response to the changes in the main circuit. This movement is not merely a mechanical gesture; it serves a crucial purpose. By shifting positions, these auxiliary contact components signal whether the main circuit is in an open or closed state.

3. Control Logic:

Beyond monitoring the status of the circuit, auxiliary contacts also engage in control logic. They have the ability to initiate specific actions based on predetermined conditions. For instance, they might be programmed to open or close contacts in response to changes in voltage, current, or other critical parameters.

4. Interlocking Mechanisms:

Imagine a scenario where conflicting operations could lead to equipment damage. Auxiliary contacts come to the rescue with interlocking mechanisms. These mechanisms ensure that certain operations can only occur when others are in a specific state, preventing any unwanted clashes within the electrical system.

5. Signalling Functions:

In more sophisticated setups, auxiliary contacts are employed for signalling purposes. When a fault occurs or maintenance is required, these contacts can trigger alarms or indicators. This signalling function enhances the safety and reliability of the electrical system by promptly alerting operators to potential issues.

Auxiliary contacts come in various types, each tailored to meet specific needs within diverse electrical systems. Understanding the distinctions between these types is essential for selecting the right auxiliary contacts for your facility in New Zealand or any similar setting.

1. Instantaneous Auxiliary Contacts:

These auxiliary contacts act swiftly in response to changes in the primary contacts. As the name suggests, they provide an instantaneous signal, making them ideal for applications where rapid response and precise timing are crucial. Industries with high-speed machinery often benefit from the use of instantaneous auxiliary contacts.

2. Delayed Auxiliary Contacts:

In contrast to instantaneous contacts, delayed auxiliary contacts introduce a time delay before they respond to changes in the main circuit. This delay can be adjusted to accommodate specific requirements, making them suitable for applications where controlled timing is essential, such as in motor control circuits.

3. Normally Open (NO) and Normally Closed (NC) Contacts:

Auxiliary contacts can also be categorized based on their default state. Normally Open (NO) contacts remain open when the main circuit is in a normal state, closing only when a specific condition is met. On the other hand, Normally Closed (NC) contacts are the opposite, remaining closed until a specific condition prompts them to open.

4. Form C Contacts:

Form C contacts combine the characteristics of both NO and NC contacts in a single unit. This versatile type of auxiliary contact provides the flexibility to accommodate a variety of control scenarios. Form C contacts are particularly useful when a single device needs to perform multiple functions.

5. Mirror Contacts:

Mirror contacts, also known as auxiliary mirror contacts, replicate the status of the main contacts. They provide an additional layer of redundancy by offering a mirror image of the primary contacts' state. This redundancy enhances reliability, especially in critical applications where a backup indication is crucial.

1. Motor Control Centers (MCCs):

In motor control centres, auxiliary contacts are frequently employed to monitor the status of motors. They provide essential feedback about whether the motor is running, stopped, or experiencing any issues. This information is vital for operators to maintain control and diagnose potential problems promptly.

2. Circuit Breakers:

Auxiliary contacts integrated into circuit breakers serve multiple purposes. They can indicate whether the circuit breaker is in the open or closed position, offering a visual confirmation of the state of the electrical circuit. Additionally, these contacts may play a role in the automatic tripping or resetting of the circuit breaker in response to specific conditions.

3. Contactors in HVAC Systems:

Heating, Ventilation, and Air Conditioning (HVAC) systems often rely on contactors for controlling the power supply to compressors and other components. Auxiliary contacts associated with contactors assist in monitoring and managing these complex systems. They contribute to the safe and efficient operation of HVAC equipment.

4. Lighting Control Panels:

In lighting control panels, auxiliary contacts are instrumental in managing the on/off status of lights. They can be programmed to activate lighting circuits based on specific conditions, such as time of day or occupancy. This not only enhances energy efficiency but also contributes to overall facility security.

5. Industrial Automation:

Auxiliary contacts play a pivotal role in industrial automation setups. They assist in coordinating the movement of machinery, ensuring that different components operate in synchronization. The signalling and interlocking functions of auxiliary contacts contribute to the overall safety and efficiency of automated processes.

Selecting the right auxiliary contacts is a critical decision that directly influences the performance and reliability of your electrical system. Here are key considerations to guide you through the process:

1. System Voltage and Current Ratings:

Begin by assessing the voltage and current requirements of your electrical system. Ensure that the auxiliary contacts can handle the specific voltage levels and current loads without compromising safety or performance. Exceeding these ratings can lead to premature wear and potential failures.

2. Operating Environment:

Consider the environmental conditions in which the auxiliary contacts will operate. Factors such as temperature extremes, humidity, and exposure to corrosive substances can impact their longevity. Choose auxiliary contacts with appropriate environmental ratings to ensure reliable performance in your facility's specific conditions.

3. Type of Load:

Different types of loads, such as resistive, inductive, or capacitive, can affect the wear and tear on auxiliary contacts. For example, inductive loads like motors can generate higher voltages during switching, necessitating auxiliary contacts designed to handle such conditions. Tailor your selection based on the nature of the loads in your system.

4. Response Time Requirements:

Consider the response time needed for your application. Instantaneous auxiliary contacts are suitable for scenarios requiring rapid reactions, while delayed contacts allow for adjustable time delays. Understanding the timing requirements of your system ensures that auxiliary contacts align with your operational needs.

5. Contact Configuration:

Evaluate the contact configuration required for your specific application. Decide whether normally open (NO), normally closed (NC), or a combination of both (Form C) contacts best suit your control and monitoring needs. The right configuration enhances the efficiency and safety of your electrical system.