BS Ultra Rapid Fuses & Fuse Holders

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The quickest way to place an order is to give our customer service team a call or send us an email. We promise to respond within 4 hours or you get $100 off your next order, however we usually respond within 1-2 hours to email enquiries. So go ahead and speak to us, we'd love to help you with your needs.

Fuse Products

• For all orders over $100 (excl. GST & freight), freight is FIS (Free into Store).
• For all orders under $100 (excl. GST & freight), a freight charge of $25 + GST is applicable.
• Additional fees may apply for deliveries to the Northern Territory and remote areas.

All Other Products

• Freight charges POA (Price on Application)
• FOT (Customer nominates own carrier and accepts all charges)

Freight details

Semiconductor fuses are fuses that have been specifically designed to protect semiconductor devices. They are often also referred to as solid state fuses, rectifier fuses or ultra-rapid fuses. Semiconductor devices are extremely sensitive to current fluctuations and require special protection. To perform this function, semiconductor fuses are able to open the circuit (blow) significantly quicker than other fuse types, and it is extremely important that they are replaced by direct equivalents when required. Semiconductor fuses belong to the utilisation categories aR, gR and gS. 

The I²t value of a fuse is a measure of the energy which is required to open the fuse element and to interrupt the current. It is determined by factors such as the design of the fuse element, the type of filler, etc. The I²t value is also a direct measure for the let-through energy which is exposed to the item being protected by the fuse in case of an over-current situation. It is a function of current squared and time, hence it is expressed in A²s (amps x amps x seconds).

Semiconductor fuses are not selected like other fuse types. The main selection criteria for a semiconductor fuse is its I²t value…. even more important than its current rating! This is because semiconductor devices are extremely sensitive to current fluctuations and the maximum amount of let-through energy that they are exposed to during an over-current needs to be accurately controlled. This is super-important when selecting fuse protection for semiconductor devices.

If you are replacing an existing fuse, make sure that the new selected fuse has an I²t value that within ±10% of the original fuse’s I²t value. In this case, I²t values need to be compared at the same system voltage.

If you are selecting a semiconductor fuse for a new application, the I²t value of the selected fuse must be lower (or quicker) than the lowest I²t value of any of the components being protected. This ensures that the fuse opens before allowing any damaging let-through current to reach the components. In addition, refer to the question ‘Can I enclose a semiconductor fuse in a fuse holder?’ in this section. 

Semiconductor fuses run hotter than most fuses. In order to achieve a very accurate melting temperature, these fuses have been engineered with a high proportion of pure silver in their element and their body filling is high quality silica, which helps to draw heat away from the fuse element. Due to this fact, it is generally accepted that they should not be enclosed so as to ensure sufficient cooling of the fuses so they can operate as specified. Fuse cooling is very challenging if the fuse holder doesn’t allow sufficient airflow around the fuse.

The ‘power loss’ value of a fuse is a measure of the heat emanating from the fuse under full load. It is used to determine how quickly the fuse dissipates its heat. This is also known as the ‘heat loss’, ‘watts loss’ or ‘heat dissipation value’. Power loss is measured in Watts. If any fuse is to be used in a fully enclosed holder, then the power loss rating of the fuse holder used must be greater than that of the fuse to ensure that there is sufficient dissipation of the heat around the fuse. In other words, the fuse holder’s ability to tolerate heat must be higher than the heat the fuse produces. If this is not followed, the fuse holder may warp, melt or explode. Due to the fact that semiconductor fuses run much hotter than type gG or type aM fuses, extra care must be taken when choosing fuse holders for them. 

Please don’t! If you do, then in the event of an over-current, you run the risk of experiencing critical damage to the semiconductor devices in the circuit. In plain words, your expensive components will blow before your fuse does.