Mersen Products

High-speed fuses are specifically designed to protect semiconductors with ultra-fast opening times (<1ms) and low I2t values. Standard fuses are slower (10-100ms) and designed for general circuit protection. High-speed fuses actively limit peak fault current and control arc voltage to protect expensive semiconductor devices like IGBTs and diodes.

Use high-speed fuses for semiconductor protection. Use standard fuses for general circuit protection.

Select fuse voltage rating at least 20% above maximum system voltage including transients. For 400V systems, use 500V fuses. For 800V EV systems, use 1000V fuses. Always verify the fuse AC or DC rating matches your application - DC ratings are typically lower than AC for the same fuse.

Select voltage rating 20% above maximum system voltage. Verify AC/DC rating matches application.

I2t (I-squared-t) is the measure of thermal energy that passes through a fuse during a fault. For semiconductor protection, the fuse I2t must be less than the semiconductor's withstand I2t. High-speed fuses have very low I2t values, limiting thermal stress on protected devices. Always verify I2t coordination in your protection design.

Ensure fuse I2t is less than semiconductor withstand I2t. Contact our FAE for coordination analysis.

Breaking capacity must exceed maximum prospective fault current. Typical requirements: 100kA for industrial power systems, 150kA-200kA for large semiconductor applications, 50kA-100kA for EV and energy storage. Calculate fault current based on power source characteristics and select fuse with at least 25% margin.

Calculate maximum fault current and select fuse with 25% margin. Contact our FAE for assistance.

Fuse coordination ensures selective protection - only the device closest to fault operates. Key principles: 1) Time-current curves should not overlap; 2) Downstream fuse operates faster than upstream; 3) I2t let-through of upstream exceeds melting I2t of downstream; 4) Maintain 2:1 current ratio between levels. Perform coordination study for complex systems.

Perform coordination study using time-current curves. Contact our FAE for complex systems.