Overview
The Mersen A480R3R-1 Amp-Trap fuse is a back-up R-rated medium voltage motor protection fuse designed for short-circuit protection of medium voltage motors and motor controllers in industrial electrical systems. This 1-barrel back-up current limiting fuse offers 100 A capacity at 4800 VAC with 65 kA interrupt rating and Class R classification. Also sold under the Gould Shawmut and Ferraz Shawmut brand names, this is a drop-in replacement for equivalent medium voltage protection applications.
Key Features
- Current-limiting, high interrupting rating (65 kA) for short-circuit protection
- Back-up fuse design requiring coordination with overload relays in combination motor starters
- Size D (3-inch diameter) barrel with ferrules and spring-reinforced clip mounting
- Visual indicating element and epoxy construction; RoHS compliant and UL listed (UL 9F60)
- Operates at both 2400V and 4800V systems (50/60Hz)
- Motor starter manufacturer generally specifies the R-rated fuse size for coordinated protection
Technical Specifications
Key ratings and physical dimensions for system integration and cabinet planning:
- Rated Current: 100 A
- Voltage Rating: 2400V / 4800V AC (50/60Hz)
- Interrupt Rating: 65 kA @ 4800V
- Class: R (back-up fuse for motor circuits)
- Barrel Diameter: 3 inches; Length: 15.97 inches
- Terminal Type: Ferrule (clips)
- Construction: Epoxy with indicating element
Typical Applications
The A480R3R-1 is commonly used in:
- Medium voltage motor circuits (2.4 kV – 4.8 kV systems)
- Motor controller and starter protection in industrial facilities
- OEM and retrofit installations requiring Class R coordination
- Plants with synchronous or squirrel-cage induction motors rated 1 HP and above
- Coordination with motor overload relays in NEMA-rated starters
Compatibility & Replacements
Compatible With
- NEMA-rated motor starters and combination starters
- Medium voltage switchgear and motor control centers (MCCs)
- Molded-case circuit breakers and disconnect switches rated for 4.8 kV systems
- Spring-reinforced clip-mounted fuse holders designed for 3-inch ferrule barrels
- Industrial electrical systems operating at 2400V or 4800V, 50/60 Hz
Replaces / Drop-In Replacement For
- Gould Shawmut A480R3R-1 (original manufacturer branding)
- Ferraz Shawmut A480R3R-1
- Equivalent 100A 4800V Class R back-up fuses from other major manufacturers
Works With
- R-rated fuse coordination standards (NFPA, IEC, IEEE)
- Motor overload relays and thermal protection devices
- Medium voltage feeder protection schemes
- UL 9F60 current-limiting fuse systems
