Motor Starting Bolt-in

Bolt-in R-rated Motor Starter Fuses are current-limiting, high interrupting rating fuses intended for the short-circuit protection of medium voltage motors and motor controllers. R-rated fuses are back up fuses that have a minimum interrupting rating, and must be coordinated with overload relays in combination motor starters. Elements of these fuses are designed to withstand the cyclic motor-starting application. The motor starter manufacturer generally specifies the R-rated fuse size. R-rated fuses are rated 2R to 36R. Most are UL Recognized.


  • Bolt-in mounting interchangeable with other brands of fuses.
  • 3 inch Diameter with bolt-in centers of 12.81 for 2.75KV and 17.88 for 2.75/5.5KV and 8.25KV. Single and Double Barrel.
  • For indoor use in or for use in a weatherproof enclosure.
  • Indicating
  • Interrupting ratings of 65,000 amps for 2.75/5.5KV and 50,000 amps for 8.25KV fuses.



  • Short circuit protection of medium voltage motors and motor controllers.



  • R-Rating: An "R" rated fuse will melt in the range of 15 to 35 seconds at a value of current equal to 100 times the "R" number. Prior to the institution of "R" ratings, motor fuses were rated by current. The Attached chart gives the proper conversion to current standards.
  • Back-up Current Limiting: A current limiting fuse which can interrupt any current in between its rated minimum interrupting current and its rated maximum interrupting current. Back-up fuses are not intended to be used as overload devices.


  • Bussmann
  • Eaton Cutler Hammer Westinghouse
  • Ferraz Shawmut


Data Sheets:

  • Data Sheet 8: Bolt-in Style "R" Rated Fuses