All you should know about high speed fuse
What is High Speed Fuse?
A high-speed fuse, also known as a fast-acting fuse, is a type of electrical safety device designed to protect electrical circuits and equipment from over-current or short-circuit conditions. These fuses are designed to quickly interrupt the flow of electrical current when an over-current event occurs, thus preventing damage to the circuit or connected equipment.
What is the role of quartz sand in fuses?
One of the primary roles of quartz sand in fuses is to enhance the arc-quenching capability of the fuse. Quartz sand has high thermal conductivity and insulating properties, with a large contact area with the electrical arc.
When a fuse operates and interrupts a high-current fault, an electrical arc forms between the melting fuse element’s ends. Quartz sand is used to fill the arc-quenching chamber within the fuse. As the arc enters this chamber, the quartz sand helps to cool and quench the arc by absorbing the heat generated. This facilitates a faster and more reliable interruption of the electrical circuit, ensuring that the fault current is quickly extinguished.
What’s the structure of North American Style High Speed Fuse？
The EV&EVSE High-Speed Fuse boasts a sophisticated structure with a fiberglass main housing, chosen for its high dielectric strength, effectively withstanding high voltages to prevent breakdown. This material minimizes the risk of unintended electrical contact and enhances safety against electrical shock or short circuits.
A copper-silver hybrid as a fuse element offers superior electrical conductivity, thermal stability, and corrosion resistance, balancing cost and performance. Silver’s high melting point ensures stability during normal operations, while quickly melting under overload conditions, providing adaptability to meet different circuit requirements.
Copper, as a material for the end connector, offers excellent electrical and thermal conductivity, mechanical strength, and corrosion resistance, while being cost-effective.
How do I select a suitable high speed fuse?
When selecting a fuse, the primary consideration is the rated voltage, which is the nominal voltage value at which the fuse can safely interrupt under specific conditions:
- Ensure the safety interrupting voltage is generally ≥1.1Un; for AC690V circuits, it should be ≥1.05Un, with some categories requiring it to be ≥Un.
- Consider the impact of circuit inductance (L) on interrupting capability. In AC circuits, power factor (cosf) is a key indicator, while in DC circuits, time constant (L/R) is the critical parameter.
- Consider the rated current (In) when selecting a fuse, reflecting its safe current passage under standard conditions. Align it with the circuit’s load and expected over-current to ensure long-term reliable performance. For North American gN and gD classes, the fuse’s rated current should exceed the applied load current multiplied by 1.25.
- The fuse style, size, structure, and connections carefully for short-circuit protection, ensuring compatibility with system requirements. Comply with relevant certification standards for the fuse’s standard system. Focus on protection current range and characteristics based on the category to meet application requirements.
- Consider altitude-induced corrections to the current-carrying capacity parameter. For every 100 meters in altitude, the fuse’s temperature rise may increase by 0.1-0.5k. In enclosed environments, derate rated current by 2%-5% for every 1000 meter increase in altitude. Altitude impacts air insulation strength, necessitating checks and corrections. Derating is unnecessary under normal conditions below 2000 meters.
