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We’re all familiar with thermally activated fuses, where the conducting element self-heats due to current flow, melts at a defined current value, and breaks the flow path. They are simple in concept (although they have their own subtleties, of course), reliable, do one thing, do it well, and provide a first (or last) line of defense against overcurrent damage in a system.

They come in many variations including fast acting, time-delay, and slow-blow, to best-fit the needs of the application. Among the reasons their use is mandated by regulatory codes in so many installations is that they need no initialization, set-up, or software, and can’t be hacked or overridden, all of which adds to their credibility and confidence in their performance.

Current-handling ranges of fuses that most engineers encounter span a fraction of an amp to tens of amps. They come in myriad packages, ranging from the classic 3AG to larger cartridges, as well as blade style used in many cars, Figure 1.

Figure 1 Fuses are available with different current ratings, of course, but also countless packages, including the 3AG glass cylinder, ceramic cartridges of various sizes, and the automotive “blade” style. Sources: RS-Online; Automation Direct; and Harbor Freight Co.

But then I started to wonder: How do they make fuses for hundreds of amps? What’s their packaging? Do the fuses simply get proportionally larger as the current goes to those levels?

My “ignorance” is largely due to lack of exposure to the topic. Higher-power engineering was not a big thing at most engineering schools for many years. That specialty, which encompasses larger-scale power generation, storage, transmission, battery energy storage systems, and solar/wind installations, was considered a backwater niche and not as exciting as designing data networks, devising and coding algorithms, or building faster computers.

But that was then, and times have changed. Today, power engineering is a hot area with all the activity related to electrified vehicles (EVs and HEVs), renewable energy, powering data centers, backup power systems, and more. Look at it this way: an EV draws on the order of 100 A and more, so fusing capabilities must be ramped up to meet appropriate engineering and regulatory requirements. Clearly, this is not a place where electric fuses (e-fuses) alone are suitable.

Would such a fuse be ten times bigger than a standard 10-A fuse? Were there any design shifts of which I should be aware?

I looked into it, and I found there’s a large subclass of thermal fuses dubbed “high rupturing capacity” (HRC) fuses which may be bigger but otherwise look like regular fuses on the outside, yet have an invisible, inside twist: they are filled with sand (silica) or other material, Figure 2.

Figure 2 (left) The HRC fuse features a filler, usually sand; (right) the actual internal construction is more complicated, as shown by this one version (there are others, as well).  Sources: Electrical Maker and Swe-Check Pty Ltd

The main design elements that differentiate an HRC fuse from a lower-current conventional fuse—called a low breaking capacity (LBC) fuse—are:

• A heat-resistant, strong outer-fuse body, usually constructed from ceramic or fiberglass; LBC devices instead often have glass enclosures which are more likely to fragment when fusing action is initiated and the overload current is high.
• The cavity inside the fuse body is filled with fine silica sand or quartz to absorb the heat and energy of an over-current. In some cases, other materials such as powdered chalk, plaster of paris, or marble dust are used, but purified sand is most common.
• The metal caps or tags are solidly attached to the fuse body to create an air-tight seal to prevent any energy escaping in the event of an overload.

Why bother to do this? To my simplistic lower-current thinking, it seemed that once the fuse link overheats and opens, there’s not much to worry about.

But in the reality of the high-current world, that sort of simplistic thinking is misguided and even dangerous. The purpose of sand in the fuse is primarily to act as a heat-absorbing medium and to prevent the arc from continuing once the fuse element melts, Figure 3. That allows the fuse to safely interrupt very high fault currents (often several thousand amps) without causing damage to the fuse holder or surrounding equipment.

Figure 3 The current versus time characterization of the HRC fuse has some interesting transitions and jumps. Source: Electrical Maker

The sand or other filler in these fuses plays multiple roles:

• Cooling: When the fuse element melts due to excessive current, the sand absorbs heat, helping to cool the area and prevent fire or damage to surrounding components.
• Arc suppression: If a fuse blows, it can create an electrical arc. The sand helps to extinguish this arc by absorbing energy and providing a medium in which the arc can dissipate safely.
• Isolation: The sand can help to isolate the molten metal of the fuse element, preventing it from causing further short circuits or damage.
• Enhanced safety: By reducing the risk of arcing and overheating, sand contributes to the overall safety and reliability of the fuse.

In short: in an ordinary fuse—a length of exposed wire—the wire will melt and thus break the circuit; so far, so good. However, if a large current is flowing, the wire will also partially vaporize, and permit an arc to be formed. This arc may not be quenched even by the AC zero-volt crossing (and certainly won’t be for a DC circuit) but can continue for many cycles. The sand in the HRC fuse prevents the arc from forming, allowing the circuit to be opened safely and remain so.

There are two points here. First, it is not just a matter of “scaling up”. As with almost every other technical component, when you push the boundaries of capacity or size, things change and important enhancements to existing solutions are needed. While the laws of physics don’t change, their manifestations do. After all, in the electromagnetic spectrum, both gigahertz/terahertz waves and optical waves are defined by Maxwell’s equations, but their realities are very different. This is the case with high-current arcing across the open circuit presented by the blown fuse wire.

The second point nothing is as simple as it seems to be. When someone says, “what’s the big deal? It’s just a fuse” of similar, it really means they don’t know what’s involved. Even a simple function such as a fuse has its own design and fabrication issues that need to be understood and resolved.

Have you ever encountered a component which had unexpected design aspects due to its need to operate under harsh conditions or parameter extremes such as (but not limited to) voltage, current, temperature, or physical stress? Did you come to understand what had been done, and why?

Bill Schweber is an EE who has written three textbooks, hundreds of technical articles, opinion columns, and product features.

Related Content

• E-fuses: warming up to higher-current applications
• Goodbye 3AG fuse, we’ll miss you
• Is there anything silicon can’t do?
• Fuse failures
• An accurate resettable fuse

The post High rupture capacity fuses: same idea, different reality appeared first on EDN.

Київська політехніка створює просвітницький простір «Інклюзивний лекторій» kpi пт, 10/25/2024 - 23:09

Pfeiffer Vacuum of Aßlar, Germany, a member of the Busch Group headquartered in Maulburg, Baden-Württemberg (in the tri-country region of Germany, France and Switzerland), has introduced its new name and refreshed logo, marking its evolution into Pfeiffer Vacuum+Fab Solutions. The rebranding reflects the portfolio of Pfeiffer as a one-stop supplier for both vacuum solutions and semiconductor fab solutions...

Epiwafer and substrate maker IQE plc of Cardiff, Wales, UK has appointed Mark Cubitt to its board as an independent non-executive director and (in first-half 2025, following a period of transition with current chair Phil Smith) as chair-elect...

III–V Epi Ltd of Glasgow, Scotland, UK — which provides a molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD) service for custom compound semiconductor wafer design, manufacturing, test and characterization — notes that its director of epitaxy Dr Neil Gerrard is among the expert contributors to the white paper ‘Epitaxially regrown quantum dot photonic crystal surface emitting lasers’...

Here's the method I use for renewing crusty soldering tips. If you keep yours cleaned and tinned, you shouldn't have to do this often if at all. Forgive my dirty workbench. You will need: * Power drill * High grit sandpaper (300, 400, 600) * Rosin core solder, or a can of tip tinner Remove the tip from the iron and mount it in your drill. Do not overtighten; hand tight should be sufficient. (Picture 2) Try a higher grit before using a lower one. This one wasn't bad so I started with 400 (picture 3) After several passes with one grit, move to the next higher and continue polishing. (Picture 4) 600-800 should be fine for most. Once your tip is clean and shiny, clean it with a solvent (isopropanol, acetone, etc) and mount it in your iron. Do not contaminate the tip with oils from your fingers. Clean it again once it's in the iron, if you have to. (Picture 5) If you are using the solder method, clean a length of solder and wrap it tightly around the tip. You only need one layer, and you do not need to wrap the entire shank; only the plated surface should be wrapped. Set your iron to operating temperature and let it warm up (Picture 6) If using solder, the solder should melt and tin your tip. If youre using tip tinner, drag the tip across the tinner while turning it slowly. (picture 7) Use brass wool to gently wipe the tip clean, and re-tin using a small amount of solder. (Picture 8) Your tip is now ready for use. If storing it make sure you keep it tinned. The shank will quickly become discolored again from oxidation and burning volatiles; this is normal, but you can clean it if desired with mild steel wool or high grit sandpaper. submitted by /u/V0latyle [link] [comments]

Гліб Скопик. Випробування розуму та особистості Інформація КП пт, 10/25/2024 - 15:28

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Led by Dr Andreas Fiedler at Germany’s Leibniz-Institut für Kristallzüchtung im Forschungsverbund Berlin e.V. (IKZ), the ‘All-GO-HEMT’ project aims to develop modulation-doped β-(AlxGa1-x)2O3/Ga2O3 heterostructures that exhibit high electron mobility. With total project funding of almost €2m, financed by the German Federal Ministry of Education and Research (BMBF), this project is expected to lead to a considerable increase in efficiency in power electronics and thus make a significant contribution to sustainable energy generation...

Led by Dr Andreas Fiedler at Germany’s Leibniz-Institut für Kristallzüchtung im Forschungsverbund Berlin e.V. (IKZ), the ‘All-GO-HEMT’ project aims to develop modulation-doped β-(AlxGa1-x)2O3/Ga2O3 heterostructures that exhibit high electron mobility. With total project funding of almost €2m, financed by the German Federal Ministry of Education and Research (BMBF), this project is expected to lead to a considerable increase in efficiency in power electronics and thus make a significant contribution to sustainable energy generation...

ams OSRAM GmbH of Premstätten, Austria and Munich, Germany has unveiled its new OSLON UV 3535. Serving the growing demand for mercury-free and efficient UV-C disinfection and treatment solutions, the UV-C LED offers 115mW output power from a single chip at 265nm, which is the emission wavelength providing the highest germicidal effectiveness. Combined with what is claimed to be outstanding wall-plug efficiency (WPE) of 5.3%, the optimized system solution has been specifically designed for the UV-C disinfection market...

🎥 Співпраця КПІ ім. Ігоря Сікорського та Асоціація саперів України: плани, напрями, форми kpi пт, 10/25/2024 - 10:57

Alarm that counts using a 7-segment display. Added the ability to use a single scr to latch and power an led with a battery, since the most important element is to have a way to know whether someone is inside waiting to do you harm. A single led accomplishes this. Here's the pcb, and Photoshop even gives me the ability to label it. I simple head over to my local library, and have them print this onto this special paper with their laser printer, and then iron & etch it. https://i.redd.it/16nes7xdttwd1.gif submitted by /u/The_Mr_Nemo15 [link] [comments]

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Microchip’s RTG4 FPGAs with lead-free flip-chip bumps have achieved QML Class V qualification, the highest level for space components. This status, designated by the Defense Logistics Agency, ensures exceptional reliability and longevity for critical space missions. QML Class V-qualified products also help customers streamline their design and certification processes.

According to Microchip, the RTG4 radiation-tolerant FPGA with lead-free flip-chip bumps is the first of its kind to gain QML Class V status. Flip-chip bumps are used to connect the silicon die and the package substrate, while the lead-free material extends the longevity of the product. The flip-chip bump is contained within the FPGA package, so converting to these new RTG4 FPGAs has no impact on the user’s design, reflow profile, thermal management, or board assembly process.

With a flash-based fabric, RTG4 FPGAs deliver high density and performance for space applications, consuming significantly less power than equivalent SRAM-based FPGAs. They also exhibit zero configuration upsets in radiation environments, eliminating the need for mitigation measures.

The RTG4 FPGAs are supported by development kits, mechanical samples, and daisy chain packages for board validation and testing. To learn more, click the product page link below.

RTG4 series product page

Microchip Technology 

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

The post Rad-tolerant FPGAs earn QML Class V status appeared first on EDN.

With a 2000-V breakdown voltage, Infineon’s IDYH80G200C5A CoolSiC Schottky diode suits systems with DC link voltages up to 1500 V. The Gen 5 silicon carbide (SiC) diode offers current ratings from 10 A to 80 A, making it well-suited for solar and EV charging applications.

The diode comes in a TO-247PLUS-4-HCC package with 14-mm creepage and 5.4-mm clearance, supporting up to 80A. This enables developers to reach higher power levels with half the component count compared to 1200-V solutions. The reduced component count simplifies the overall design and eases the transition from multilevel to two-level topologies.

Infineon’s .XT interconnection technology enhances the Schottky diode’s resistance to humidity, extending system lifetime. According to the company, it also significantly reduces thermal resistance and impedance, improving heat management.

The IDYH80G200C5 CoolSic Schottky diode is available now.

IDYH80G200C5 product page

Infineon Technologies 

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

The post SiC diode handles high DC link voltages appeared first on EDN.

The RX260 and RX261 groups of 32-bit MCUs from Renesas feature a capacitive touch sensing unit with high noise immunity and water resistance. These 64-MHz microcontrollers consume 69 µA/MHz when active, dropping to 1 µA in standby mode. With their low-power operation and touch capabilities, the RX260/RX261 MCUs are well-suited for home appliances, building and factory automation, e-bikes, and smart locks.

Based on an RXv3 CPU core, the devices achieve a CoreMark score of 355 at 64 MHz, up to 2.5 times higher than comparable 64-MHz MCUs. Renesas also reports 25% lower active current and 87% lower standby current than similar MCUs, enabling customers to meet strict energy regulations for home appliances and extend the operating time of battery-powered equipment.

The capacitive touch IP (CTSU2SL), included as an HMI function, offers multi-frequency scanning to reduce false detection due to external noise and an automatic judgement function to detect touch events without CPU activation. QE for Capacitive Touch V4.0.0, a development assistance tool, simplifies the initial settings of the touch user interface and sensitivity tuning.

In addition, RX261 microcontrollers feature RSIP-E11A security IP with built-in AES, ECC, and SHA encryption engines and security management features. They also add full-speed USB and CAN FD interfaces.

Both the RX260 and RX261 groups of MCUs are available now from Renesas and authorized distributors.

RX260 product page 

RX261 product page 

Renesas Electronics 

Find more datasheets on products like this one at Datasheets.com, searchable by category, part #, description, manufacturer, and more.

The post Low-power MCUs enable capacitive touch sensing appeared first on EDN.