The **GMA-4-R** is a specific type of subminiature, fast-acting glass tube fuse commonly used in electronic circuits to protect against overcurrent conditions. Below is a detailed breakdown of its electronic specifications and characteristics. ### 1. General Specifications The part number "GMA-4-R" follows a standard naming convention in the electronics industry (often associated with manufacturers like Eaton/Bussmann). | Feature | Specification | | :--- | :--- | | **Type** | Glass Tube Fuse | | **Current Rating** | 4 Amperes (4A) | | **Voltage Rating** | 125V AC / 250V AC (Standard) | | **Response Speed** | Fast-Acting (F) | | **Material** | Glass Body, Nickel-plated Brass Endcaps | | **Standard Size** | 5mm x 20mm | | **RoHS Compliant** | Yes (indicated by the "-R" suffix) | --- ### 2. Electronic Characteristics #### A. Fast-Acting Mechanism Unlike "Slow-Blow" (Time-Delay) fuses, the GMA-4-R is designed to open very quickly when the current exceeds its 4A rating. * **Purpose:** It protects sensitive electronic components (like semiconductors, ICs, and transistors) that cannot withstand even brief surges. * **Opening Time:** It typically opens within milliseconds at 200% of the rated current. #### B. Interrupting Rating This refers to the maximum current the fuse can safely stop without physically exploding or arcing. * For a 4A GMA fuse, the interrupting rating is typically **200A at 125V AC** or **100A at 250V AC**. #### C. Resistance and Voltage Drop Every fuse has a small amount of internal resistance. As 4A flows through the GMA-4-R, a small voltage drop occurs across the fuse, which is dissipated as heat. In a 4A fuse, the cold resistance is typically very low (approximately **0.020 to 0.030 Ohms**). --- ### 3. Physical Construction The physical design ensures compatibility with standard fuse holders and PCBs. * **Glass Body:** Allows for visual inspection. You can see if the internal filament is broken (blown). * **5x20mm Dimensions:** This is the "European" standard size, distinct from the larger 1/4" x 1-1/4" (6.3x32mm) American fuses. * **Endcaps:** Conductive caps that snap into fuse clips or screw-cap fuse holders. --- ### 4. Typical Applications The GMA-4-R is found in various electronic devices where 4 Amps of protection is required: 1. **Consumer Electronics:** Power supplies for monitors and small appliances. 2. **Audio Equipment:** Amplifiers and mixers. 3. **Industrial Controls:** Control panels and PLCs. 4. **Lighting:** Ballasts and LED drivers. --- ### 5. Part Number Breakdown ```text GMA - 4 - R | | | | | +-- RoHS Compliant (Lead-Free) | +------ Amperage Rating (4 Amps) +----------- Series Name (5x20mm Fast-Acting Glass Fuse) ```