250NHM2B-690

Specialty fuses, such as the 250NHM2B-690, are designed for use in industrial circuits as part of AC 3-phase switchgear, and provide protection from dangerous and high fault currents from damaging sensitive equipment. This type of specialty fuse offers a number of advantages to the user, including an easily recognizable design, low maintenance requirements, a high degree of protection, and a fast short-circuit response time. This article will explore the application of the 250NHM2B-690 and discuss its working principle.

Application

The 250NHM2B-690 specializes in protection of high rated current 3-phase installations and equipment from any possible over-currents, which can arise from short-circuits. It is especially important for protecting sensitive electrical and electronic components. This type of specialty fuse is rated for a maximum of 400A and features reliable operation at voltages of up to 690V.In addition to its primary purpose of over-current protection, the 250NHM2B-690 also provides the advantage of rapid overload clearance. This is due to the integration of two separate melting units and a thermal limiter which functions as either a safety device or back-up unit.

Working Principle

The 250NHM2B-690 is designed to protect sensitive AC 3-phase equipment from dangerous and high fault currents. The fuse works by connecting three terminals in a panel, typically a Neutral, a Phase and an Earth. When the fault current is greater than the fuses rated current, the electrical signal triggers the release of the internal contacts which activate the fuse and begins the process of melting the fuse wire. The release of the internal contacts, breaks the electrical circuit, preventing the flow of electricity and stopping the fault current from further damaging the equipment.The thermal limiter integrated into the fuse is a safety device which can act as a back-up unit in the event that the breaker fails to actuate or disconnect the power supply. The limiter is capable of withstanding extreme high temperatures, approximately 1000 °C, which allows for fast overload clearance. When the temperature drops back down to a safe level, the limiter will automatically re-close the circuit and reconnect the power supply.

Conclusion

The 250NHM2B-690 provides a number of advantages for the user, including its easily recognizable design, low maintenance requirements, a high degree of protection, and a fast short-circuit response time. It offers over-current protection for sensitive AC 3-phase equipment and features a thermal limiter to provide an additional layer of protection. Understanding the application and working principle of this type of specialty fuse can help users ensure the safety of their circuits and equipment.