EATON Class J 600Vac Fast-Acting, Time Delay and High-Speed Fuses

EATON Class J Current Limiting Power Fuses
600 VAC – 200,000 Amp Interrupting Rating



In previous articles we’ve discussed Class T and Class L fuses. In future articles we’ll continue the discussion covering RK1, RK5, G, H and CC class fuses.

Here we’ll discuss various EATON Class J current limiting fuses. Class J is one of the more common classes of fuses. For a discussion of current limiting fuses, see the Monster Blog article on how current-limiting fuses work.

To develop their fuse safety test procedures, the U.S, Europe and Asia established classes with defined performance standards. In the case of power fuses, these standards have evolved into distinct classes. Understanding fuse characteristics of these classes simplifies specifying fuses.

Class J fuses are commonly used in branch circuits, motor circuits, mains, feeders, control panels, electronic motor controllers, drives, soft-starters, circuit breaker back-up, transformers, load centers, lighting, heating and general loads to name a few.

Class J Fuse Safety Specifications

Class J Fuse safety is guided by UL standards identified by classes of low-voltage (600 volts or less) fuses.  All U.S. fuse makers certify their Class J fuses at a 200,000 amp interrupting rating (I.R.) at 600Vac with the exception of the Bussmann LPJ series, which is certified with a 300,000A interrupting rating.

Many of the manufacturers have self-certified their Class J fuses up to 300,000A I.R. at 600Vac. In addition, some Class J products carry a DC rating and a corresponding interrupting rating. Interrupting rating is the current that a fuse, circuit breaker, or other electrical apparatus is able to interrupt without being destroyed or causing an electric arc with unacceptable duration.

Class J fuses are available in time delay, fast acting or high speed types, and they are non-renewable. This means they can’t be returned to service after operation. They have no renewable elements.

Below is a summary of Class J fuses from Eaton Bussmann and Edison, with links to their datasheets and complete specifications (including AC and DC ratings and I.R.) for use in typical applications.







Eaton Bussmann LOW-PEAK® LPJ Time-Delay Power Fuses

The Eaton Bussmann LPJ power fuses are the only UL Listed and CSA Certified fuses with a 300kA interrupting rating allowing worry-free installation in virtually any application.

Bussmann fuses are a great Class J choice in dual-element fuses and are available in indicating and non-indicating versions. They are designed with a minimum 10 second time delay at 500% overload which reduces fuse opening caused by in-rush currents and surges.

Class J 600V fuses can usually be sized for motor burnout backup circuit protection if other overload protection fails. LOW-PEAK® fuses have exceptional current which protects components downstream against thermal and magnetic effects of short circuit currents.

LOW-PEAK® LPJ 1-60A Data Sheet 1006
LOW -PEAK® LPJ 70-600A Data Sheet 1007


Eaton Bussmann DFJ High Speed Power Fuses

Eaton Bussmann DFJ drive fuse is a high speed, current-limiting fuse. They provide maximum protection for AC and DC drives and controllers and are easily coordinated with existing and new drives and controllers. For more details, see previous Bussmann DFJ fuse article.

Fuse element alloy, conductivity, and construction give high speed fuses their current-Bussmann-DFJlimiting 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.

DFJ fuses come in standard Class J dimensions allowing the use of readily available fuse blocks, holders and switches and have the lowest let-through energy of any branch circuit overcurrent protective device.

DFJ High Speed Drive Fuse Data Sheet 1048

Eaton Bussmann JKS Fast Acting Power Fuses

EATON’s Bussmann Limitron™ JKS Class J fast-acting current-limiting fuses are available in ratings from 1 to 600 amps. Bussmann JKS fuses are also available in a special, UL® Recognized 700Vac version in select ratings. See page 4 of Data Sheet 1026,Limitron-JKS below.

JKS Class fast-acting fuses provide 10X better current limitation to help prevent equipment damage caused by short-circuit events. This means they’re ideal for critical industrial or commercial applications that have specific current limitation requirements.

JKS fast-acting Class J fuses up to 60A Data Sheet 1026
JKS fast-acting Class J fuses 70 to 600A Data Sheet 1027

Eaton Edison Series JDL Time-Delay Power Fuses

Edison JDL dual-element time delay fuses have a minimum 10 second time-delay at 500% overload. This means a long time-delay that minimizes needless fuse openings duejdl-fuse to temporary overloads and transient surges.

JDL power fuses also can be sized for back-up protection against motor burnout from overload or single-phasing if other overload protective devices fail.

JDL 600Vac, 1 to 60A Data Sheet 1303
JDL 600 Volt, 70 to 600A Data Sheet 1304

Eaton Edison JFL Fast-Acting Power Fuses

Edison JFL fast-acting, current-limiting fuses provide superior short-circuit protection which makes them a good choice for protecting low interruption capacity circuit breakers.jfl-fuse

On older systems, available short-circuit current may exceed the interrupting capacity of the circuit breakers. These fuses can be installed in series with existing older equipment. EATON’s Edison JFL fuses are ideal for lighting and heating circuits and other non-inductive loads.

JFL 600Vac, 1 to 60A Data Sheet 1305
JFL 600Vac, 70-600A Data Sheet 1306

Correct Fuse Sizing for Safe Installation
and Reliable Circuit Protection

The above Class J fuse summaries should help you choose the right fuse to ensure safe installation and optimal circuit protection in today’s electrical distribution systems.

Understanding the fuse characteristics of the various fuse classes simplifies specifying and selecting fuses to avoid mistakes that could jeopardize equipment and component systems. Proper fuse selection depends on many factors, so consult a professional engineer for your application.


Monster Fuses is a Factory Authorized Provider of Eaton Bussmann, Eaton Edison and Littelfuse Class J Fuses. Monster Fuses also provides Mersen Class J Fuses and the industry’s largest factory authorized of Medium & High Voltage Power Fuses and Power Fuse Hardware from all the major fuse lines.


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.


Monster Fuses provides immediate shipment of power fuses, hardware 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.


Monster Controls provides immediate shipment of 5kV Class control components. Clients can access thousands of 5kV class control parts from an extensive inventory, eliminate long factory lead times and supply real time solutions for electrical control challenges. Specializing in parts for 2.3kV, 5.5kV and 7.2kV motor starters, contactors and switches, Monster Controls also stocks complete starters, contactors and switches.



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