Littelfuse KLSR400 400A Class RK1 Fast-Acting Fuse – Knife-Blade – 600VAC/300VDC

The Littelfuse KLSR400 is a Class RK1 fast-acting current-limiting fuse designed for high-performance short-circuit protection in industrial and commercial electrical systems. Built with a single-element silver link construction, it delivers rapid response to fault conditions. It is commonly used to protect surge-sensitive equipment such as variable speed drives, rectifiers, and electronic systems, but may require oversizing in motor or inductive load applications to avoid nuisance operation due to inrush currents.

Voltage and Rating

• Current Rating: 400 Amps
• Voltage Rating: 600 Volts AC
• DC Voltage Rating: 300 Volts DC
• Interrupting Rating: 200 kA AIR (up to 20 kA @ 300 VDC)

Key Specifications

• Fuse Type: Fast-Acting (F)
• Fuse Class: Class RK1
• Mounting Type: Knife-Blade
• Series: KLSR
• Family Style: Current Limiting Fuse
• Application: Short-circuit protection for industrial electrical systems

Technical Specifications

• Opening Characteristic: Fast-Acting
• Current Limiting: Yes
• Interrupt Amperage: 200,000 Amps
• Construction: Single-element silver link design
• Suitable For: Variable speed drives, rectifiers, surge-sensitive equipment
• Safety Rating: High interrupting capacity reduces need for extensive short-circuit analysis

Product Data

• Manufacturer: Littelfuse
• Model Number: KLSR400
• Series: KLSR RK1 Fast-Acting Fuse

Features

• Extremely current-limiting for fast fault interruption
• Reliable protection up to 200 kA available fault current
• Helps reduce equipment damage from short-circuit energy
• Knife-blade design for standard fuse holders
• Ideal for industrial distribution and electronic protection systems