The **FRS-R-7-1/2** is a specific model of industrial-grade fuse manufactured by **Bussmann (Eaton)**. It belongs to the **Fusetron™** series and is designed for high-performance protection in electrical circuits. ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Model Number** | FRS-R-7-1/2 (or FRS-R-7.5) | | **Amperage Rating** | 7.5 Amps | | **Voltage Rating** | 600 Vac (or less), 300 Vdc (or less) | | **Interrupting Rating** | 200,000A RMS Symmetrical (Vac), 20,000A (Vdc) | | **Class** | RK5 | | **Fuse Type** | Dual-Element, Time-Delay | | **Physical Size** | 5.0" x 0.81" (Standard 600V RK5 dimensions) | --- ### 2. Functional Characteristics #### A. Dual-Element Design The FRS-R-7-1/2 contains two distinct components inside its body: 1. **Thermal Element:** Handles low-level overloads. It has a specific "time-delay" feature that allows temporary surges (like motor startups) to pass without blowing the fuse. 2. **Short-Circuit Element:** A high-speed notched ribbon that reacts almost instantaneously to heavy short-circuit currents to prevent catastrophic equipment damage. #### B. Time-Delay Feature This fuse provides a minimum of **10 seconds** of delay at 500% of the rated current. This is critical for circuits involving induction motors or transformers where "inrush current" is significantly higher than the normal operating current. #### C. Current Limitation As a Class RK5 fuse, it is "current-limiting." This means it can physically restrict the amount of peak energy that flows through the circuit during a short circuit, protecting downstream components from magnetic and thermal stress. --- ### 3. Common Applications * **Motor Protection:** Specifically for individual motor circuits where 7.5A covers the Full Load Amps (FLA) requirements. * **Transformer Protection:** Protecting the primary or secondary side of control power transformers. * **Branch Circuit Protection:** Used in industrial safety switches and fuse blocks to protect electrical distribution. * **Mains and Feeders:** Suitable for general-purpose circuits where a 600V rating is required. --- ### 4. Comparison: FRS-R vs. FRN-R It is important not to confuse the **FRS-R** with its sibling, the **FRN-R**: | Series | Voltage Rating | Color Code | | :--- | :--- | :--- | | **FRS-R** | 600 Volts | Green Labeling | | **FRN-R** | 250 Volts | Orange/Yellow Labeling | ---