Class T Low Voltage Fuses from EATON Bussmann, Littelfuse, Mersen, Edison

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Safety is the Main Concern of Class T Low Voltage fuses mandated by industry in circuit protection. To develop their low voltage power fuse safety test procedures, the U.S, Europe and Asia established safety and performance standards. In the case of power fuses, these standards have evolved in into distinct classes of low-voltage (600 volts or less) fuses, Classes RK1, RK5, G, L, T, J, H and CC being the more important.

Here we’ll take a look at Class T fuses, low voltage, fast acting fuses that are different from the EATON Bussmann Time-Delay fuses discussed in last article. See EATON Bussmann Class L Fuses for Protection of Feeders and Service Entrance Equipment.

Below you’ll find specification sheets for EATON Bussmann Class T, Littelfuse Class T, Mersen Class T and Edison Class T fast-acting fuses.


 These “space savers” used to protect
surge-sensitive components are less than
1/3 the size of equivalent Class R fuses. 

Fast Acting Vs. Time Delay: What’s the Difference?

Time delay fuses are designed to withstand in-rush currents or surge currents when powering up or down. Fast acting fuses on the other hand “blow” quickly to immediately prevent equipment damage caused by short circuit events. They are common in electrical equipment (versus power transmission, power distribution and motor applications) that quickly emit intense heat.

Fast Acting Class T fuses are extremely current limiting and rated to interrupt a minimum of 200,000 amps at 600Vac. Class T fuses come in 300Vac and 600Vac varieties, with amp ratings from 1 to 1200 amps. DC ratings and corresponding interrupting capacities vary from manufacturer to manufacturer, so review each product carefully for DC applications. Their small space-saving footprint is about 1/3 the size of a comparable Class R Fuse, and the unique physical design prevents replacement by other fuse classes.

Typical Class T fuse applications include load centers, panelboards, switchboards, circuit breakers, metering centers, variable speed drives, inverters, rectifiers, UPS systems, power supplies and more.


Class T Fast-Acting Fuse Features and Benefits

  • Exceptionally current-limiting for low peak let-thru current
  • Fast-acting fuse prevents equipment damage caused by short-circuit events
  • Unique dimensions prevent replacement by other fuse classes
  • Small physical size for greater design flexibility
  • Ideal for applications having specific current limitation requirements
  • Ideal for system upgrading when existing circuit breakers cannot safely interrupt larger available short-circuit currents


Class T Data Sheets: Key Features & Specifications

Bussmann Class T JJN Limitron™ 300Vac, 1-1200A Data Sheet 1025
Bussmann Class T JJS Limitron™ 600Vac, 1-800A Data Sheet 1029
Edison Class T TJN 300Vac, 1-1200A Data Sheet 1319
Edison Class T TJS 600Vac, 1 to 800A Data Sheet 1320
Littelfuse CLASS T JLLN/JLLS POWR-GARD® Data Sheet
Mersen Class T A3T/A6T Power Fuses


Monster Fuses is a Factory Authorized Provider of EATON Bussmann Class T, Edison Class T, Littelfuse Class T, and Mersen Class T Power Fuses and Hardware.

Fuse Selection and Sizing
for Protecting Electrical Equipment

Electrical Equipment systems and components handle a wide range of currents. You can avoid fuse sizing mistakes when selecting and correctly sizing fuses for electrical equipment and component systems. Proper fuse selection depends on many factors, so consult a professional engineer for your application.


Monster Electrical is a “knowledge-based” independent distributor of fuses, fuse hardware and 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 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.


Call 888-444-4335 in the West or 877-444-1798 in the EAST.
Need help calculating fuse current ratings for transformers or selecting fuse hardware, power equipment and electrical replacement parts?



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