The **FRS-R-75** is a high-performance industrial fuse belonging to the Fusetron™ series, manufactured by Eaton (Bussmann Division). It is a Class RK5 current-limiting, dual-element, time-delay fuse designed for heavy-duty electrical protection. --- ### ## Technical Specifications The following table highlights the core electrical characteristics of the FRS-R-75: | Property | Value | | :--- | :--- | | **Amperage Rating** | 75 Amps | | **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 | | **Element Type** | Dual-element (Time-delay) | | **Body Material** | Fiberglass tube | --- ### ## Key Features and Electronic Functionality #### 1. Dual-Element Design The FRS-R-75 contains two distinct components that handle different types of electrical faults: * **Thermal Cutout:** Handles long-term overloads. It allows temporary surges (like motor startups) to pass without blowing the fuse but will open if a sustained overload occurs. * **Short-Circuit Element:** A fast-acting component that triggers instantly during high-current short circuits to prevent catastrophic damage. #### 2. Time-Delay Characteristic This fuse is specifically engineered to provide a minimum of **10 seconds** of delay at 500% of the rated current. This is critical for circuits containing motors or transformers that pull high "inrush" current when first turned on. #### 3. Current Limitation The FRS-R-75 is "current-limiting." In the event of a massive short circuit, the fuse reacts so quickly that it interrupts the current before it even reaches its full potential peak. This reduces the magnetic and thermal stress on downstream components like breakers and contactors. #### 4. Rejection Feature The "R" in FRS-R denotes a rejection feature. The fuse has a specific physical notch in its end cap that prevents it from being replaced by a lower-rated or non-current-limiting fuse (like a Class H fuse) in a compatible fuse block. --- ### ## Common Applications * **Motor Branch Circuits:** Providing both overload and short-circuit protection. * **Transformers:** Handling the initial magnetization inrush current. * **General Power Distribution:** Used in switchboards and panelboards where 600V protection is required. * **Inductive Loads:** Any circuit with high starting currents.