The **3SB-4-R** refers to a specific type of **Miniature Glass Tube Fuse** commonly used in electronics to protect circuits from overcurrent and short-circuit conditions. --- ### 1. Technical Specifications The "3SB" series is typically manufactured by brands like **Bel Fuse** or **Bussmann**. Below are the core specifications for the **3SB-4-R** model: | Parameter | Specification | | :--- | :--- | | **Current Rating** | 4 Amperes (4A) | | **Voltage Rating** | 250V AC | | **Fuse Type** | Slow-Blow (Time-Delay) | | **Physical Size** | 6.3mm x 32mm (1/4" x 1-1/4") | | **Body Material** | Glass | | **Termination Style** | Cartridge (Ferrule) | | **RoHS Compliant** | Yes (indicated by the "-R" suffix) | --- ### 2. Key Features * **Slow-Blow Functionality:** Unlike "Fast-Acting" fuses, the 3SB-4-R is designed to withstand temporary surges in current (such as motor startups or power-on inrushes) without blowing immediately. It will only open the circuit if the overcurrent persists. * **Transparent Glass Body:** The glass construction allows for easy visual inspection. If the internal filament is broken or the glass is blackened, the fuse is blown and needs replacement. * **Standard Dimensions:** The 6.3mm x 32mm size is a global standard for North American small-dimension fuses, making it widely compatible with standard fuse holders and clips. --- ### 3. Common Applications The 3SB-4-R is utilized in devices where initial power-up requires more current than the steady-state operation: 1. **Consumer Electronics:** Power supplies for desktop computers and older television sets. 2. **Industrial Equipment:** Small motors, actuators, and control panels. 3. **Appliances:** Microwave ovens and coffee makers that have inductive loads. --- ### 4. Part Number Breakdown Understanding the nomenclature helps in identifying equivalent parts: | Segment | Meaning | | :--- | :--- | | **3SB** | Series prefix (Slow-Blow, Glass Tube) | | **4** | Amperage rating (4 Amps) | | **-R** | Lead-free / RoHS Compliant | ---