The **FRS-R-4/10** is a specific model of industrial-grade power fuse manufactured primarily by **Bussmann (Eaton)**. It belongs to the **Fusetron™** series and is designed for high-performance circuit protection. --- ### 1. Technical Specifications The model number "FRS-R-4/10" contains coded information about its electrical characteristics: | Feature | Specification | | :--- | :--- | | **Model Series** | FRS-R (Fusetron Dual-Element, Time-Delay) | | **Current Rating** | 0.4 Amps (4/10 A) | | **Voltage Rating (AC)** | 600 Vac | | **Voltage Rating (DC)** | 300 Vdc | | **Interrupting Rating** | 200,000A RMS Symmetrical (at 600V) | | **Fuse Class** | Class RK5 | | **Physical Size** | 5 inches length × 0.81 inches diameter | --- ### 2. Key Electronic Features #### A. Dual-Element Design The FRS-R-4/10 contains two distinct components working in tandem: 1. **Thermal Element:** Handles low-level overloads. It provides a "time-delay," allowing temporary surges (like motor startups) to pass without blowing the fuse. 2. **Short-Circuit Element:** A fast-acting component that opens almost instantaneously if it detects a high-magnitude short circuit. #### B. Time-Delay Characteristics This fuse is engineered to hold a current of **500% of its rated capacity** for a minimum of **10 seconds**. This is critical for circuits involving small motors or transformers that have high "inrush" currents but stabilize quickly. #### C. Current Limitation As a Class RK5 fuse, it is "current-limiting." This means in the event of a catastrophic short circuit, the fuse reacts so quickly that it interrupts the current before it can reach its full peak magnitude, protecting downstream sensitive electronics. --- ### 3. Common Applications Because of its low amperage (0.4A) and high voltage rating (600V), this part is typically used in: * **Control Transformers:** Protecting the primary side of industrial control power circuits. * **Solenoids:** Preventing burnout in electromagnetic coils. * **Small Motor Branch Circuits:** Providing overcurrent protection for specialized low-power machinery. * **HVAC Systems:** Used in industrial heating and cooling control panels. --- ### 4. Safety & Standards * **UL Listed:** Standard 248-12, Class RK5. * **CSA Certified:** Standard C22.2 No. 248.12. * **Rejection Feature:** The "R" in FRS-R indicates a physical rejection notch. This prevents a user from accidentally replacing it with a lower-rated fuse (like a Class H or K) that doesn't have the same safety interrupting capacity.