The **5HFP 4-R** is a specific type of electronic component belonging to the **Subminiature Fuse** family, manufactured primarily by **Bel Fuse Inc.** It is designed for space-constrained applications requiring reliable overcurrent protection. --- ## 1. Technical Specifications The 5HFP series consists of high-speed, ceramic body fuses. Below are the primary specifications for the **5HFP 4-R** variant: | Parameter | Specification | |:---|:---| | **Current Rating** | 4 Amperes (4A) | | **Voltage Rating (AC)** | 125V / 250V | | **Interrupting Rating** | 100A @ 250V AC / 10,000A @ 125V AC | | **Melting Integral ($I^2t$)** | ~11.8 $A^2s$ | | **Body Material** | Ceramic | | **Termination Style** | Axial Leaded (Through-hole) | | **Operating Temperature** | -55°C to +125°C | --- ## 2. Key Features and Meaning of the Part Number The part number **5HFP 4-R** can be broken down to understand its physical and electrical characteristics: ### A. "5HFP" - Series Code * **5x20mm Form Factor:** This indicates a subminiature size, typically used on Printed Circuit Boards (PCBs). * **Fast Acting:** This fuse is designed to open (blow) quickly when an overload occurs, protecting sensitive semiconductors and ICs. * **High Interrupting Capacity:** The "H" denotes a higher breaking capacity compared to glass-tube fuses. ### B. "4" - Amperage * Represents the **4 Amp** continuous current rating. ### C. "-R" - Compliance * **RoHS Compliant:** The "-R" suffix indicates that the part is lead-free and meets European environmental standards for hazardous substances. --- ## 3. Typical Applications Because of its small size and high-speed response, the 5HFP 4-R is commonly found in: * **Power Supplies:** Protecting the input stages of AC/DC converters. * **Monitors and Displays:** Safeguarding internal circuitry in LCD/LED screens. * **Industrial Controllers:** Used on PCBs where space is at a premium. * **Consumer Electronics:** Chargers, adapters, and home appliances. --- ## 4. Comparison: Fast-Acting vs. Time-Delay It is critical not to confuse the **5HFP** (Fast-acting) with the **5HTP** (Time-delay/Slow-blow) series. * **5HFP:** Trips almost instantly upon reaching a specific threshold. Use this for sensitive electronics. * **5HTP:** Allows for temporary "inrush" currents (like a motor starting). Substituting a fast-acting fuse with a slow-blow one can lead to circuit damage.