1.1 Function of Fuses

When the current in a circuit becomes too high, the metal components inside the fuse melt and break the circuit, thereby protecting equipment and devices. This process, where the fuse melts due to a large current, is called "blowing the fuse." Once a fuse has operated, it must be discarded and replaced. Fuses can operate in both DC and AC circuits. In residential and commercial buildings, circuit breakers are more commonly used, but a large fuse is still needed to protect the entire system from short circuits or electrical surges. In electronic devices, almost all power supplies are equipped with fuses.

1.2 Principle of Fuses

Fuses typically consist of a wire or thin metal strip installed between two terminals. These parts are enclosed in metal canisters, ceramic cylinders, or glass tubes. Fuses are sensitive to current but not to voltage. When selecting a fuse, it's important to consider the constant current loss. A safe method is to calculate the maximum current when all components are operating and then add 50%. For surges or pulses, the duration must be considered. Any fuse will exhibit resistance when current flows through it; otherwise, the current would not generate enough heat to blow the fuse. Manufacturer specifications list the voltage drop created by the internal resistance of the fuse in the circuit.

1.3 Fuse Parameters

The rated current of a fuse is printed on its casing. The rated current is the maximum current that the fuse can handle continuously at an ambient temperature of 25°C. If the fuse and other heat-generating components are enclosed in the same housing, the actual ambient temperature of the fuse will be higher than the external environment. Ideally, a fuse should reliably operate at its rated maximum current and blow when the current exceeds its rated value by 20%. In practical applications, the continuous load on a fuse should not exceed 75% of its rated value. The rated voltage of a fuse is the maximum voltage at which the fuse can safely blow in case of current overload. A fuse can operate continuously at voltages below its rated voltage and still provide protection.

1.4 Fuses for EV Charging

Fuses come in various types, including small fuse tubes, automotive fuses, blade fuses, plug-in fuses, resettable fuses, and surface mount fuses. For charging station output terminals, where the voltage reaches above 750V, ceramic tube fuses and fiber tube fuses are typically used.

Bussmann, a professional fuse manufacturer, offers a wide range of solutions for EV Charging. Bussmann provides 800VDC and 1000VDC fuses for the DC output of EV Charging, known for their performance and availability. Let's briefly look at some of these fuses:

800VDC Fuses:

CBX000S-800 Series Fuse: Rated voltage 800VDC, aR fuse, rated current from 32A to 400A, breaking capacity of 50kA, compliant with IEC60269-4 / GB13539.4 standards, ceramic tube fuse. Advantages include small size, suitable for compact ev charging designs.

1000VDC Fuses:

FWE Series Fuse: Rated voltage 1000VDC, aR fuse, rated current from 70A to 600A, breaking capacity of 50kA, compliant with IEC 60269-4, UL 248-13 recognized, and CE standards, fiber tube fuse. Advantages include comprehensive certification, meeting the requirements of both European and North American markets, with a maximum current of up to 600A.

CBX000S-1000 Series Fuse: Rated voltage 1000VDC, rated current 25A to 250A, breaking capacity of 50kA, compliant with IEC60269-4 / GB13539.4 standards, ceramic fuse. Advantages include compact size.

CBX01S-1000 Series Fuse: Rated voltage 1000VDC, rated current 32A to 400A, breaking capacity of 50kA, compliant with UL248 standards, ceramic fuse, rectangular shape. Versions with indicators available, can be used with microswitches like the 170H0069.

1.5 How to Choose?

Any device plugged into a wall socket should have a fuse installed, not only to protect its components but also to safeguard the personnel operating it. High-power motors, pumps, or other high-power devices should use slow-blow fuses to handle the initial current surge when the equipment is turned on, which might exceed the fuse's rated value. Slow-blow fuses can withstand surges for a few seconds. Fast-blow fuses are used in circuits that are sensitive and can be easily damaged. Any battery-powered device needs a fuse because, in the event of a short circuit, the battery may cause unpredictable results.