Bussmann DFJ Fuses for Semiconductor Protection

Bussmann DFJ Class J High Speed Fuse

Bussmann DFJ
Class J
High Speed Fuses

Protecting AC, DC Drives and Other Semiconductor Applications with High Speed Power Fuses

We know that all power fuses are a safety device consisting of a metal strip or wire fuse element that melts and breaks an electric circuit if the current exceeds a safe (i.e., overloaded, faulted) level. High speed power fuses have some unique characteristics. After reading this post you’ll understand high speed fuses and why the Bussmann DFJ fuse is especially suited for protecting AC and DC drives and other semiconductor applications.

What makes a “high speed” fuse different?

In large part, the answer lies in the alloy used and the reduced sections, or “necks”, in that little strip of metal. The alloy and reduced sections allow the fuse to operate at higher temperature levels while ensuring fast opening through rapid element melting to protect semiconductors. In addition, the body (or barrel) material used is often a higher grade with a higher degree of thermal conductivity. This design allows heat to dissipate quickly into the atmosphere.

Fast “clearing time” — the time that it takes the fuse to open and stop current flow — explains why Bussmann DFJ Class J fuses are considered High Speed fuses. This high speed current-limiting fuse’s heat dissipation and fast clearing time provides maximum circuit protection for AC and DC drives and other semiconductor applications.

How Electrical Fuse WorksFuse Anatomy: Necks and Weak Spots

Modern high speed fuses come in many shapes and sizes, but they share the same key features. Although all fuse components affect fuse operation and performance, a key determining factor in how they operate, as mentioned above, is the fuse element. High Speed fuse elements are made from high conductivity material and designed with a number of reduced sections called “necks” or “weak spots.”

Weak spots in fuse construction cause arcing (electrical discharge) that contributes to fuse element melting. Bussmann High Speed fuses, like all high speed fuses, quickly conduct heat away from the fuse without exceeding pre-set maximum temperatures of the fuse element or other components.

Bussmann DFJ Class High Speed Fuse Features

• Easily coordinated with existing and new variable speed drives and electric controllers.

• Standard Class J dimensions allow using readily available fuse blocks, holders and switches.

• Has the lowest let-through energy of any branch circuit overcurrent protective device.

Fuse element alloy, conductivity, and construction give high speed fuses their current-limiting ability to protect semiconductors in AC and DC drives and controllers from the damaging heat caused by an overload or overvoltage. Bussmann DFJ Class fuses will help protect your investment in AC and DC drives and other power control equipment using power semiconductor devices.

Bussmann DFJ Fuse Stock items:DFJ-5, DFJ-6, DFJ-15, DFJ-20, DFJ-25, DFJ-30, DFJ-40, DFJ-45, DFJ-50, DFJ-60, DFJ-70, DFJ-80, DFJ-100, DFJ-125, DFJ-150, DFJ-200, DFJ-225, DFJ-250, DFJ-300, and DFJ-400.

Avoiding Costly Power Fusing Mistakes

Power distribution systems come in all sizes and configurations and handle a wide range of currents. You can avoid fuse sizing mistakes when selecting and correctly sizing replacement fuses by consulting a professional engineer for your application. Monster Fuses can point you in the right direction.


Monster Electrical is a “knowledge-based” independent distributor of fuses, fuse hardware and 5kV Class control equipment. We don’t just ship boxes. Our product and application knowledge goes into every transaction. When you Need-It-Now we are ready, 24/7.


Monster Fuses provides immediate shipment of power fuses and power fuse mountings from our extensive inventory. Clients can access more than 14,000 power fuse solutions provided from a stock of 100,000+ fuses, eliminate long factory power fuse lead times and supply real time solutions for urgent fuse challenges in utility, industrial, institutional and commercial applications.


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