NO NC contactor full form is Normally Open and Normally Closed contactor. Before proceeding further, let me briefly introduce what a contactor is.
A contactor serves as an electrical switch that monitors and controls a circuit. People use them to connect or disconnect a circuit. It offers a more advanced alternative to electric relays. The NO NC relay handles a higher current capacity than a basic relay.
A NO (Normally Open) contact remains open until a predefined specific condition occurs. By default, a NO switch does not conduct current; it needs to be energized to allow current to flow.
An NC (Normally Closed) contact remains closed until a specific condition is met. By default, the NC contact lets current flow until it becomes de-energized.
Modular Contactors Supporting NO and NC Contact Status
Distinguishing Points Between Normally Open And Normally Closed Contacts
In order to acquire a smooth NO NC contactor connection, having a sound understanding of the differences between the two types of contactors is mandatory. Let us dive into their differences concerning functionality, applications, and advantages.
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Structural Difference
The contacts are open in NO contactor. It indicates the gap with a spring between the fixed and moving contacts. The gap is filled, and the circuit is closed when the coil is energized and pulls the movable contact towards the fixed one.
In contrast, the NC contact is a closed contact where the moving contact is connected to the fixed one. Once the coil is energized, the movable contact is pushed away from the fixed contact, thus opening the circuit.
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Functional Difference
a. Normal State
In their normal or de-energized state, the NO NC contactor working is opposite to each other. The Normally Open Contactor has an open circuit, and no current flows through it. In contrast, the normally closed Contactor lets the current flow through the closed circuit in its normal state.
b. Energized State
In their energized state, they work opposite from the normal state; the Normally Open Contacts lets the current flow through the circuit. On the other hand, the normally closed Contactor stops the current from flowing through the circuit in its energized state.
NO and NC Contacts in Their Normal and Energized States
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Terminal Colors
Some contactors, specifically push button switch NO NC contactors, can be distinguished based on color. It is done intentionally to avoid damage and incidents. The NC contactor’s plastic cap or label is marked red or pink as it is done with push buttons and emergency stops.
The NO contactor is often marked with green or blue to mark the start. The choice of colors is made keeping in view the outlook of masses that red denotes danger, and green is a go or start signal.
Note: However, it must also be noted that it is not a universal standard of color for a contactor NO and NC. Many manufacturers use their own scheme of colors to mark NO NC contacts or the blue or white color for auxiliary terminals.
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Labelling
While outlining the NO NC contactor wiring diagram, the contacts are labelled with specific NO and NC symbols to distinguish them. Two lines with a gap represent NO contact, whereas two lines intersected by another line represent the NC contact.
2 Pole Contactor with 1 NO and 1 NC Contacts
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Applications of NO NC Contactors
The NO contactor is suitable where the circuit is completed only when needed, such as in motors or lights. A switch completes and activates the circuit as required. They provide a perfect solution for industrial or commercial setups with a strong need for control and immediate response.
The NC contacts are preferred for situations where safety is the foremost concern, such as emergency stop buttons and interlock. It is installed to ensure that operations remain smooth until there is an emergency or urgency to shut down the machine.
Moreover, you can get a 2 pole NO NC contactor and a 4 pole NO NC contactor as per your need.
4 Pole Contactor with 2 NO and 2 NC Contacts
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Advantages
The No contactor gives you the advantage of energy conservation as they are used for machines and systems that are turned on as required. They are a simple and budget-friendly option.
On the other hand, the NC contactor, closed by default, lets the continuous power supply through the circuit. They are ideal for devices that must be run continuously for prolonged periods. They are a reliable option with the capacity to handle high voltages.
The best part is that these contacts are available separately and in a combined unit to make things easier. The additional benefit is that the replacement of the NO NC contactor is relatively easy and simple.
How Do You Select The Most Suitable NO NC Contactor?
After going through the guide about both types of contactors, the question arises: how do you select the most suitable NO NC contactor? Let us briefly guide you through the main criteria for choosing the best option for your power distribution.
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Determining The Type Of Contactor
The first step is to determine the purpose of the contactor so as to decide which type of contactor goes well with the requirement. You must be aware of the application of the contactor for the kind of load: resistive or inductive.
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Voltage Rating
Always make sure to check the voltage rating of the contactor. It must be capable enough to handle the highest current that may pass from the system. Almost all the manufacturers specify details about their contacts for customers’ convenience.
NO NC Contactor Wiring Diagram
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Auxiliary Contacts
They are additional contacts in the contactors. Their purpose in the contactor is not to stop or start any circuit like NO NC, but they act as a signalling tool in any contactor, providing additional safety.
NO NC Switch Wiring
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International Safety Standards
You must ensure that the contactors meet the international safety standards, as it may indicate their reliability and efficiency in handling electric loads safely.
Frequently Asked Questions (FAQs)
1. Why Is NO NC Contactor A Better Alternative To Regular Switches?
The NO NC switch is a better alternative to regular switches due to its functionality and safety. They can handle heavy loads promptly and efficiently without the risk of overheating. They last longer than regular switches and minimize the risk of electric shocks or incidents.
2. Can A NO Contactor Be Transformed Into An NC One?
No, an NO contactor cannot be transformed directly into an NC contactor. They are both designed specifically for different operations and use different techniques. However, the NO and NC contactors are available in one unit.
3. What To Look For While Selecting A Contractor?
While selecting a contact, you must be sure of the type: NO or NC. The voltage rating of the contactor must match your requirements. Also, the number of poles must be considered along with the coil ratings and voltage.
4. What Is The Lifespan Of A NO NC Contactor?
The average lifespan of NO NC contactors falls between 10 to 15 years, mainly depending on how frequently the contactors have been used. It may be possible that the minimal use, such as at emergency stops, will make the contactor last for 20 years.
Final Words
Using NO NC contactors and understanding the difference between the two is crucial for you to select the most appropriate for your electrical system. Also, according to your circuit needs and load, you can install the single phase NO NC contactor (2 poles) and 3 phase NO NC contactor (4 poles). While the NO contactor provides additional safety with the circuit being open when not in use, the NC contactor ensures smooth, uninterrupted operations by providing a closed circuit.
We are your trusted partner in making the best decision for your electric solutions. Our expertise in circuit monitoring and safety devices guarantees top-notch products with customization according to your business type. Contact us immediately to enhance your electrical system’s protection and efficiency.
