The **LPN-RK-70SP** is a high-performance, industrial-grade power fuse belonging to the **Low-Peak™** series manufactured by Bussmann (Eaton). It is designed for circuit protection in high-current applications. --- ### 1. Technical Specifications The following table highlights the core electrical characteristics of the LPN-RK-70SP: | Feature | Specification | | :--- | :--- | | **Current Rating** | 70 Amps | | **Voltage Rating (AC)** | 250 Vac | | **Voltage Rating (DC)** | 125 Vdc | | **Interrupting Rating (AC)** | 300,000 Amps (RMS Symmetrical) | | **Interrupting Rating (DC)** | 100,000 Amps | | **Fuse Class** | Class RK1 | | **Response Characteristic** | Time-Delay (Dual-Element) | | **Body Material** | Melamine glass tube with brass end caps | --- ### 2. Key Electronic Features #### A. Dual-Element Time-Delay The LPN-RK-70SP is a "dual-element" fuse. This means it contains two different internal components working in series: 1. **Thermal Element:** Handles low-level overloads. It allows temporary surges (like motor startups) to pass without blowing. 2. **Short-Circuit Element:** Acts almost instantaneously when it detects a high-magnitude short circuit to prevent catastrophic damage. #### B. Current Limitation (RK1 Classification) As a Class RK1 fuse, it is highly **current-limiting**. In the event of a massive short circuit, the fuse reacts so quickly that it prevents the current from reaching its full peak. This protects downstream sensitive electronic components and reduces the risk of arc flash. #### C. High Interrupting Rating With a 300,000A interrupting rating, this fuse is capable of safely clearing extremely high fault currents without exploding or maintaining an internal arc, which is critical for industrial power distribution. --- ### 3. Physical Dimensions & Indicators The "SP" suffix often denotes "Smart-Spot" technology or specific visual indicators depending on the production year, though primarily it signifies the **Superior Performance** of the Low-Peak line. * **Diameter:** Approx. 1.06 inches (26.9 mm) * **Length:** Approx. 5.88 inches (149.2 mm) * **Termination:** Blade-end (Knife blade) for secure contact in fuse blocks. --- ### 4. Common Applications * **Motor Branch Circuits:** Protection against motor burnout while allowing for high starting currents. * **Main Switches:** Used in service entrance equipment. * **Panelboards:** Protecting distribution panels from high-fault current damage. * **Inductive Loads:** Transformers and solenoids that experience inrush current.