## FRS-R-350 Electronic Part Overview The **FRS-R-350** is a specific model of a high-capacity industrial fuse manufactured by **Eaton** under the **Bussmann Series**. It belongs to the **Fusetron™** family of dual-element, time-delay fuses. --- ### Technical Specifications | Feature | Specification | | :--- | :--- | | **Model Number** | FRS-R-350 | | **Current Rating** | 350 Amperes | | **Voltage Rating (AC)** | 600 Vac | | **Voltage Rating (DC)** | 300 Vdc | | **Interrupting Rating** | 200,000A RMS Symmetrical (AC) / 20,000A (DC) | | **Fuse Class** | Class RK5 | | **Fuse Type** | Dual-Element, Time-Delay | | **Physical Size** | Large Cartridge (Blade type) | --- ### Key Electronic Components & Design The FRS-R-350 is not a simple wire; it is a sophisticated electromechanical protection device consisting of two primary internal mechanisms: #### 1. The Dual-Element Design Unlike a standard fast-acting fuse, the FRS-R-350 contains two distinct components connected in series: * **Thermal Cutout (Time-Delay):** This element handles low-level overloads. It consists of a spring-loaded mechanism held by a specialized solder alloy. It allows temporary surges (like motor startups) to pass but melts if a sustained overload occurs. * **Short-Circuit Element:** A notched copper or silver link designed to melt almost instantaneously when exposed to extremely high currents (short circuits). #### 2. Rejection Feature (Class RK5) The "-R" in the part number denotes a **Rejection** feature. This is a physical notch in the fuse blade that, when used with an R-series fuse block, prevents a lower-rated or non-current-limiting fuse (like a Class H or K) from being installed in its place. --- ### Primary Applications The FRS-R-350 is primarily used in heavy industrial settings for: * **Motor Circuits:** Its time-delay property prevents "nuisance blowing" caused by high inrush currents when a large motor starts up. * **Main Feeders:** Used in power distribution switchboards. * **Branch Circuit Protection:** Protects sensitive downstream components from massive short-circuit damage. --- ### Benefits of Use 1. **Current Limitation:** It significantly reduces the "let-through" energy during a fault, protecting downstream equipment from mechanical and thermal stress. 2. **Coordination:** Can be easily coordinated with other fuses to ensure only the fuse closest to a fault opens (selective coordination). 3. **High Interrupting Rating:** Can safely stop currents as high as 200,000 Amps without exploding or failing.