The **MDL-3-R** is a specific model of a **Time-Delay Glass Tube Fuse** manufactured by Eaton (Bussmann Series). It is widely used in electronic circuits to protect against overcurrent conditions while allowing for temporary surges. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Current Rating** | 3 Amperes | | **Voltage Rating (AC)** | 250 VAC | | **Fuse Type** | Time-Delay (Slow-Blow) | | **Physical Size** | 1/4" x 1-1/4" (6.35mm x 31.75mm) | | **Material** | Glass Tube with Nickel-plated Brass Endcaps | | **Interrupt Rating** | 100A at 250Vac / 10,000A at 125Vac | --- ### 2. Breakdown of the Model Name (MDL-3-R) * **MDL**: This is the series designation. MDL fuses are known as "Time-Delay" or "Slow-Blow" fuses. Unlike fast-acting fuses, they are designed to withstand a brief high-current "inrush" without blowing. * **3**: Represents the **Ampere rating** (3 Amps). The fuse will carry 3A continuously but will melt if the current exceeds this threshold for a sustained period. * **R**: Stands for **RoHS Compliant**. This indicates the part is manufactured without hazardous substances like lead. --- ### 3. Electronic Functionality The MDL-3-R serves a critical protective role in a circuit: #### A. Inrush Current Tolerance Electronic components like motors, transformers, and large capacitors draw a spike of current when first powered on. A standard fuse might blow immediately. The MDL-3-R uses a **coiled filament** or a specific thermal link that takes longer to heat up, allowing these spikes to pass safely. #### B. Overload Protection If a circuit fault occurs (e.g., a component shorts out) and the current stays above 3A, the internal element will melt, opening the circuit and preventing fire or further hardware damage. #### C. Visual Inspection Because the body is made of **clear glass**, it allows technicians to visually confirm if the fuse is "blown." A dark burn mark or a visible break in the wire indicates failure. --- ### 4. Common Applications * **Power Supplies:** Protecting the primary side of AC/DC converters. * **Consumer Electronics:** Used in older audio equipment, microwave ovens, and chargers. * **Industrial Control:** Protecting small motors or solenoids where startup current is high. ---