## LPS-RK-70SPI Low-Peak Fuses The **LPS-RK-70SPI** is a high-performance, current-limiting time-delay fuse manufactured by Bussmann (Eaton). It belongs to the **Low-Peak™ RK1 family**. The "SPI" suffix specifically denotes the inclusion of a **Smart-Pulse™ local indication** feature. --- ### Technical Specifications The following table summarizes the primary electrical and physical characteristics of the LPS-RK-70SPI: | Attribute | Specification | | :--- | :--- | | **Current Rating** | 70 Amps | | **Voltage Rating (AC)** | 600 Vac | | **Voltage Rating (DC)** | 300 Vdc | | **Interrupting Rating (AC)** | 300,000 Amps RMS Symmetrical | | **Interrupting Rating (DC)** | 100,000 Amps | | **Class** | RK1 | | **Fuse Type** | Time-Delay / Dual-Element | | **Indication** | Visual Indication (Smart-Pulse) | --- ### Key Electronic & Functional Features #### 1. Dual-Element Design The fuse contains two distinct components working in tandem: * **Thermal Element:** Handles low-level overloads. It provides a time-delay (minimum 10 seconds at 500% of rated current) to prevent "nuisance tripping" caused by motor startup currents. * **Magnetic/Instantaneous Element:** Consists of notched copper links that react instantly to high-level short circuits, limiting the peak let-through current. #### 2. Class RK1 Performance Being a Class RK1 fuse, it offers a higher degree of current limitation compared to Class RK5. This reduces the **Arc Flash** hazard and the mechanical stress placed on downstream components (like busbars and breakers) during a fault. #### 3. Smart-Pulse™ Indication (SPI) The "SPI" feature is an electronic/visual enhancement: * **Mechanism:** It features a built-in indicator that triggers when the fuse blows. * **Benefit:** Allows maintenance personnel to quickly identify the failed circuit in a crowded panel without needing to test every fuse with a multimeter. #### 4. Current Limitation Because it is current-limiting, the LPS-RK-70SPI clears a fault in less than half a cycle (under short-circuit conditions). This limits the total $I^2t$ (thermal energy) that travels through the system. --- ### Typical Applications * **Motor Branch Circuits:** Ideal for motors where high inrush current is present. * **Feeder and Branch Circuit Protection:** Used in industrial control panels and power distribution units. * **Transformer Protection:** The time-delay feature allows for transformer primary inrush. * **General Purpose:** Any circuit requiring a 70A, 600V protection level with high interrupting capacity. ---