The **MDA-20-R** is a specific model of a time-delay (slow-blow) ceramic tube fuse, manufactured primarily by **Eaton (Bussmann Series)**. It is a critical electronic component used for overcurrent protection in high-power applications. --- ## 1. Technical Specifications The "MDA-20-R" part number contains specific data about its electronic characteristics: | Parameter | Specification | | :--- | :--- | | **Current Rating** | 20 Amperes (20A) | | **Voltage Rating** | 250 VAC (Volts AC), 125 VDC (Volts DC) | | **Response Time** | Time-Delay / Slow-Blow (T) | | **Interrupting Rating** | 1500A @ 250VAC, 10kA @ 125VAC/DC | | **Body Material** | Ceramic (Cylindrical) | | **Dimensions** | 1/4" x 1-1/4" (6.3mm x 32mm) | | **RoHS Compliant** | Yes (Indicated by the "-R" suffix) | --- ## 2. Key Design Features ### Ceramic Construction Unlike glass fuses, the MDA series uses a **ceramic tube**. Ceramic allows for a higher interrupting rating, meaning the fuse can safely clear a much higher short-circuit current without the housing shattering. ### Time-Delay Mechanism The MDA-20-R is designed to withstand temporary "inrush" currents (surges) that occur when motors or large power supplies start up. It will not blow instantly if the current briefly exceeds 20A, but it will open if a sustained overload occurs. ### Internal Link The internal element is typically made of a heavy-duty alloy wire or a coiled filament, often surrounded by **silica sand** filler. The sand acts as an arc-quenching medium to absorb energy when the fuse blows. --- ## 3. Common Applications Due to its high amperage and time-delay characteristics, the MDA-20-R is commonly found in: * **Industrial Control Panels:** Protecting branch circuits. * **Large Appliances:** Microwave ovens, air conditioners, and dryers. * **Power Supplies:** Main input protection for high-wattage AC/DC converters. * **Motors:** Small to medium-sized electric motors that have high startup torque. --- ## 4. Part Number Breakdown Understanding the nomenclature helps in finding substitutes: * **MDA:** The series designation (Ceramic, Time-delay). * **20:** The current rating in Amperes. * **-R:** Indicates the part is lead-free and complies with RoHS environmental standards. ---