The **3SB 2.5-R** is a specific model of a miniature cartridge fuse, widely used in electronic circuits to protect against overcurrent and short-circuit conditions. Below is a detailed technical breakdown of this component. ### 1. Technical Specifications The model name follows a standard nomenclature used by manufacturers like **Bel Fuse**. | Feature | Specification | | :--- | :--- | | **Series** | 3SB (3.6mm x 10mm Miniature) | | **Current Rating** | 2.5 Amperes (2.5-R) | | **Voltage Rating** | 250V AC | | **Fuse Type** | Slow Blow / Time Delay | | **Body Material** | Glass | | **Termination Style** | Axial Leaded (Pig-tail) | | **Standards** | UL, CSA, CE | --- ### 2. Physical Construction The "3SB" series is characterized by its small form factor, often referred to as a **micro-fuse**. * **Glass Tube:** Allows for visual inspection to see if the internal filament has melted. * **Axial Leads:** The "-R" suffix typically indicates it comes with copper leads (pig-tails) attached to the end caps. This allows the part to be soldered directly into a Printed Circuit Board (PCB) without a fuse holder. * **Dimensions:** Roughly 3.6mm in diameter and 10mm in length. ### 3. Electronic Characteristics #### Slow Blow (Time Delay) Functionality The 3SB 2.5-R is a **Slow Blow** fuse. Unlike "Fast Acting" fuses, it is designed to tolerate temporary current surges (inrush current) without blowing. This is essential for: * Inductive loads (motors, transformers). * Capacitive power supplies that draw a large burst of energy upon startup. #### Current and Voltage Limits * **2.5A Rating:** The fuse will carry 2.5 amps indefinitely under normal conditions. It will open (blow) if the current significantly exceeds this value for a sustained period. * **Interrupting Rating:** This component can safely interrupt high currents (often up to 35A or 100A at 250V AC) without the glass tube shattering. --- ### 4. Common Applications Due to its small size and time-delay characteristics, the 3SB 2.5-R is commonly found in: 1. **Consumer Electronics:** Power adapters for laptops and small appliances. 2. **LED Lighting:** Drivers and ballasts. 3. **Industrial Controls:** Protecting small sensors or control circuits. 4. **Chargers:** Battery charging circuits where initial connection causes a spike. ---