## FRS-R-125 Fusetron™ Dual-Element Time-Delay Fuse The **FRS-R-125** is a high-performance industrial cartridge fuse manufactured by Eaton (Bussmann Series). It is designed to provide overcurrent protection for motors and critical circuits. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Model** | FRS-R-125 | | **Amperage Rating** | 125 Amps | | **Voltage Rating (AC)** | 600 Vac | | **Voltage Rating (DC)** | 300 Vdc | | **Interrupting Rating** | 200,000A RMS Symmetrical (AC) / 20,000A (DC) | | **Class** | RK5 | | **Fuse Type** | Dual-Element, Time-Delay | --- ### 2. Physical Characteristics The FRS-R-125 is a large-format cartridge fuse with the following dimensions: * **Length:** 9.63 inches (approx. 244 mm) * **Diameter:** 1.61 inches (approx. 41 mm) * **Construction:** Heavy-duty body with blade-style end terminals for secure mounting in fuse blocks or disconnect switches. --- ### 3. Core Features and Functionality #### A. Dual-Element Design Unlike a standard single-element fuse, this component contains two distinct internal mechanisms: 1. **Thermal Element:** Handles long-term overloads (e.g., a motor running slightly above rated current). 2. **Short-Circuit Element:** Acts instantly during a catastrophic short-circuit event. #### B. Time-Delay Property The "Time-Delay" feature is critical for motor circuits. It allows for a temporary surge in current—typically up to 500% of the rating for a minimum of 10 seconds—to accommodate the **inrush current** required to start a motor without blowing the fuse unnecessarily. #### C. Current Limitation As a Class RK5 fuse, it provides significant current limitation. This means it can "clip" the peak fault current before it reaches its maximum potential, protecting downstream equipment from mechanical and thermal stress during a short circuit. --- ### 4. Common Applications * **Motor Branch Circuits:** Its primary use case, preventing "nuisance blowing" during startup. * **Transformers:** Handling high magnetizing inrush currents. * **Main Disconnects:** Used in industrial panels to protect the entire system against high-magnitude faults.