## Technical Overview: FRS-R-25 Fuses The **FRS-R-25** is a high-performance industrial fuse manufactured by **Eaton (Bussmann Series)**. It belongs to the **Fusetron™** family and is categorized under **UL Class RK5**. It is a dual-element, time-delay fuse designed to handle high inrush currents without nuisance tripping. --- ### 1. Key Technical Specifications | Feature | Specification | | :--- | :--- | | **Current Rating** | 25 Amperes | | **Voltage Rating (AC)** | 600 Vac | | **Voltage Rating (DC)** | 300 Vdc | | **Interrupting Rating (AC)** | 200,000 Amps RMS Symmetrical | | **Interrupting Rating (DC)** | 20,000 Amps | | **Fuse Class** | Class RK5 | | **Fuse Type** | Dual-Element, Time-Delay | --- ### 2. Physical Characteristics The "R" in FRS-R denotes the **rejection feature**. This physical design ensures that the fuse can only be inserted into a Class R fuse holder, preventing the accidental installation of a fuse with a lower interrupting rating (like Class H or K). * **Construction:** Cylindrical cartridge with grooved end caps for rejection. * **Size:** Generally 5 inches in length and 0.81 inches in diameter. --- ### 3. Core Electronic Functionality The FRS-R-25 utilizes a **Dual-Element** design, which provides two distinct types of protection: 1. **Short-Circuit Protection:** A high-speed thermal-magnetic element responds instantly to massive current surges (short circuits). 2. **Overload Protection:** A spring-loaded thermal element handles temporary overloads. This allows the fuse to "ignore" the momentary high-current draw when a motor starts up, provided the current returns to normal levels quickly. ### 4. Common Applications * **Motor Protection:** Ideally suited for AC motor circuits where high startup torque creates temporary current spikes. * **Branch Circuits:** Used in industrial panels to protect wiring from overheating. * **General Purpose:** Suitable for mains, feeders, and transformers. --- ### 5. Selection Guide (Standard Cross-References) If you are looking for an equivalent part from another manufacturer, these are the industry standards: | Manufacturer | Part Number | | :--- | :--- | | **Littelfuse** | FLSR025 | | **Mersen (Ferraz Shawmut)** | TRS25R | ---