Power Electronics

Underwriters Laboratories Authorizes New Fuse and Fuse Holder Class CF

Underwriters Laboratories (UL) officially established a new fuse and fuse holder class for the next generation of circuit protection. The new Class CF, UL File numbers E4273, Vols. 6 & 7, and standard 248-17 for the fuse and 4248-17 for the holder, provides the same electrical protection of a Class J, along with finger-safe construction and smaller dimensions than the Class J fuse standard. Currently only the Cooper Bussmann® Low-Peak® CUBEFuse® overcurrent protective system - both the fuse and fuse holder - meets the new Class CF standard.

The CUBEFuse system had been previously designated as "Special Purpose" Listed Class J. The new Class CF listing removes the "Special Purpose" category and its unique marking as well as removes confusion in the industry over whether the CUBEFuse can be used where a "Listed" fuse is required.

The new Class CF is the first class with Peak Current Let-Through Curves in the standard. These curves cover the range of currents from 25kA to 300kA, and allow users to pick any available current they want. This same concept is working its way through the standards process for Class J, L and RK1.

Cooper Bussmann designed the dual element, time-delay Low-Peak CUBEFuse system as the first finger-safe power fuse and fuse holder package. The current-limiting performance of a properly sized CUBEFuse unit offers Type 2 (IEC 947-4-1) "No Damage" coordinated motor starter protection. And, as the smallest footprint of any class fuse including Class J, CC, T and RK, the CUBEFuse provides substantial space savings and installation flexibility. The ampacity rejecting CUBEFuse holder offers DIN rail or panel mounting, and is available in single-pole 30A, 60A and 100A versions that dovetail together to form the required number of poles. These holders are so compact that a 3-pole, 100A CUBEFuse holder (TCFH100N) occupies approximately 1/3 the space of a standard 100A Class J fuse block.

The fuse is also available with easyID™ indication; the indicating version (TCF) is available from 6A to 100A while the non-indicating version (TCF__RN) is available from 1A through 100A. Both offer voltage ratings of 600Vac/300Vdc. The CUBEFuse device operates in conjunction with the UL 98 Listed CCP for use in industrial control panels. The CCP is available in 1-, 2- or 3-pole versions in ratings of 30A and 60A. Note the UL 98 does not yet have the new Class CF integrated into its standard for disconnecting devices. This is being updated.

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