7.2kV Bolt-On R-Rated Motor Protection Fuses, RD Series

DENCO's RD series are 7.2kV R-rated motor protection fuses of bolt-on design. They run from 2R to 24R (70A to 450A) in a 15-7/8 in (403mm) length, tested to 80kA RMS asymmetrical and 50kA RMS symmetrical at 7200V. They carry a thermal striker and protect medium-voltage motors and motor controllers against short circuits.

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The 7.2kV table lists RD1 catalog numbers for 2R to 12R (70A to 230A) and RD2 numbers for 18R and 24R (390A and 450A). A second set with a B suffix, such as RD1-6R170B, repeats the same sizes and ratings under drawing Figures C and D, while the plain numbers appear under Figures A and B.

Minimum interrupting ratings run from 190A for the 2R to 1910A for the 24R. As with the lower-voltage ranges, the catalog defines the R rating by melting time: the fuse melts in 15 to 35 seconds at 100 times its R rating. The 7.2kV range stops at 24R; there is no 36R size at this voltage.

Specifications

Construction and options

• Bolt-on design
• Thermal striker
• Standard (Figures A, B) and B-suffix (Figures C, D) catalog numbers
• Can be designed to customer specifications

Catalog numbers in this series

Applications

• Short circuit protection of medium voltage motors and motor controllers

Curves and drawings

This series is on pp.57–58 of the January 2025 DENCO catalog. Access the catalog or ask for the drawing or curve you need.

Technical review

Specifications on this page are quoted from DENCO’s product catalog. Confirm any rating against DENCO engineering before specifying.

Related

• R-Rated Motor & Soft-Starter Fuses: the full family
• 2.5kV and 4.8kV R-rated motor fuses (RA / RC)
• All fuse product families
• Cross-reference and discontinued replacement

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