The **5SF400-R** is a specific type of **Small Dimension Miniature Fuse**. It belongs to the 5SF series, which are characterized as fast-acting glass tube fuses, typically measuring 5x20mm. --- ### 1. Technical Specifications The following table outlines the primary electrical and physical characteristics of the 5SF400-R: | Parameter | Specification | | :--- | :--- | | **Current Rating** | 400 mA (0.4A) | | **Voltage Rating (AC)** | 250 V | | **Fuse Type** | Glass Tube (Miniature) | | **Characteristic** | Fast-Acting (F) / Quick Acting | | **Dimensions** | 5mm x 20mm | | **Breaking Capacity** | 35A @ 250V AC | | **Resistance** | Approx. 0.45 - 0.60 Ohms (Cold) | | **Standards** | IEC 60127-2/2 | --- ### 2. Key Features * **Fast-Acting Performance:** Designed to open quickly when an overcurrent occurs. This is critical for protecting sensitive electronic components (like semiconductors) that cannot withstand even brief surges. * **Glass Body:** The transparent housing allows for easy visual inspection to determine if the fuse element has melted (blown). * **Nickel-Plated Brass Caps:** Ensures high conductivity and resistance to corrosion at the contact points. * **RoHS Compliant:** The "-R" suffix usually denotes compliance with RoHS (Restriction of Hazardous Substances) standards, meaning it is lead-free. --- ### 3. Common Applications Because the 5SF400-R is a low-current, fast-acting fuse, it is found in: 1. **Consumer Electronics:** Power supplies for laptops, printers, and monitors. 2. **Test Equipment:** Multimeters and oscilloscopes to protect internal circuitry. 3. **Industrial Controls:** Small PLC (Programmable Logic Controller) modules. 4. **Lighting:** Electronic ballasts and LED drivers. --- ### 4. Comparison: Fast-Acting vs. Time-Delay It is important to ensure you are using the **5SF** (Fast) version and not the **5ST** (Time-Delay) version, as their behaviors differ significantly: | Feature | 5SF400-R (Fast-Acting) | 5ST400-R (Time-Delay) | | :--- | :--- | :--- | | **Surge Tolerance** | Very Low | High (allows temporary inrush) | | **Protection Speed** | Instantaneous | Delayed | | **Best For** | Sensitive ICs, Digital Logic | Motors, Transformers, Capacitors |