Overview
The Bussmann FRN-R-400 Fusetron is a Class RK5 dual-element, time-delay, current-limiting fuse designed for motor control and industrial power distribution circuits. With a 400A rating at 250VAC/125VDC, this fuse combines high interrupting capacity (200 kA symmetrical at 250V, 20 kA DC) with proven overload tolerance, making it ideal for circuits with transient surge currents and motor starting inrush demands.
Key Features
- Dual-element design for superior motor overload and short-circuit protection
- 10-second time delay at 500% rated current—reduces nuisance trips on motor startup
- Current-limiting construction reduces let-through current during fault conditions
- Class RK5 provides selective coordination in multi-level protection schemes
- Blade-end terminal design fits standard cartridge fuse holders
- UL 248-12, CSA C22.2, and CE approvals for global safety compliance
Technical Specifications
- Rated Current: 400 A
- Voltage Rating: 250 VAC / 125 VDC
- Interrupting Rating: 200 kA (symmetrical) at 250 Vac; 20 kA at 125 Vdc
- Class: RK5 (Rejection fuse)
- Type: Dual-element, time-delay
- Time Delay Response: 10 seconds minimum at 500% rated current
- Terminal Type: Blade end × blade end
- Body Diameter: 2.38 inches
- Overall Length: 8.63 inches
- Weight: 1.94 lbs
- Material: Fiberglass cartridge with silver-sand element
- Status: Non-indicating (no open fuse indicator)
Typical Applications
- Motor control centers (MCCs) protecting 3-phase and single-phase motors
- Power panelboard protection for circuits subject to temporary overloads
- Combination motor starters with dual-element time delay requirements
- Machinery disconnects and industrial equipment feeds
- Circuits requiring 10-second hold time under 5× rated overload
Compatibility & Replacements
Compatible With
- Standard Class RK5 cartridge fuse holders and clips
- Motor control centers using blade-end fuse terminals
- Industrial electrical systems rated 250 VAC / 125 VDC
- Panelboards and combination starters designed for RK5 rejection fuses
Replaces / Drop-In Replacement For
- FRN-R-400 (all production variations)
- Equivalent Class RK5 400A dual-element fuses with 10-second time delay
Works With
- Class RK5 fuse holder systems (blade-end style)
- UL 248-12 rated electrical distribution equipment
- Industrial automation and motor control systems
- Eaton/Bussmann protective device coordination charts
