A High Speed Fuse, also known as a semiconductor fuse, is a device developed for overcurrent protection in semiconductor circuits. It features a specially designed component profile and structure to limit let-through energy, peak current, arc voltage, and other parameters in a circuit. Unlike standard industrial fuses, High Speed Fuses can respond within 10ms or even faster, ensuring more reliable protection.

01 High Speed Fuse Structure

Fuse selection criteria, as previously discussed, include working current, voltage, ambient temperature, surge current, and breaking capacity. These methods also apply to industrial fuses. However, High Speed Fuses (semiconductor fuses) are unique devices designed for semiconductor circuit protection. Their specialized structure and materials restrict let-through energy, peak current, and arc voltage. Unlike standard fuses, High Speed Fuses lack delay functions, enabling ultra-fast response (≤10ms) for enhanced protection.

High Speed Fuses are categorized into full-range gR fuses (protecting against overloads and short circuits) and partial-range aR fuses (protecting against short circuits only).
Their design, dimensions, and terminals are distinct to prevent misuse in general industrial applications. Key structural components include:

· Element: Made of silver, silver-plated copper, or other conductive materials, with reduced cross-sections to control resistance and current rating.

· Body Material: High-grade ceramics or glass-reinforced melamine for heat dissipation and durability.

· Terminals: Copper alloy or brass with anti-corrosion plating for low-resistance connections.

· Filler: Quartz silica to suppress arc discharge and stabilize thermal balance.

02 Product Voltage

High Speed Fuses cover voltages from 150V to 1500V, making them suitable for high-reliability applications and meeting the 1000–1500V requirements of new energy systems.

03 Fuse Operating Principle

During overcurrent or short circuits, the fuse element melts due to heat imbalance. Weak points in the element vaporize, creating an arc. The filler material extinguishes the arc by increasing impedance. The protection process involves melting time (element disintegration) and arcing time (arc suppression), with the total duration termed clearing time.
Key observations:

· Voltage spikes during melting are limited by the fuse’s current-restricting capability.

· Arc voltage must stay below the semiconductor’s withstand voltage to prevent damage.

04 High Speed Fuse Characteristic Curves

High Speed Fuses provide detailed curves to guide semiconductor protection design.

1. Time-Current Curve (TCC): Maps fault current (x-axis) to melting time (y-axis), with virtual pre-arcing time (tv) for short-circuit analysis.

2. Temperature Derating Curve: Adjusts current ratings based on ambient temperature.

3. Peak Let-Through Current Curve: Limits fault current to protect semiconductors.

4. Arc Voltage Curve: Ensures arc voltage stays below semiconductor tolerance (e.g., 1100V arc voltage at 500V requires 1200V-rated semiconductors).

5. Total Clearing I²t Curve: Adjusts I²t values (energy tolerance) for varying voltages to match semiconductor limits.

6. Power Loss Correction Curve: Derates power loss for lower currents using correction factor Kp.