The **LPS-RK-500SP** is a high-performance, current-limiting, dual-element time-delay fuse part of the **Bussmann Low-Peak™** series. These are typically used in industrial and commercial power distribution systems to protect motors, transformers, and branch circuits. --- ## 1. Technical Specifications The "LPS-RK-500SP" designation contains specific information about its electrical characteristics: | Feature | Specification | Description | | :--- | :--- | :--- | | **Series** | LPS-RK | Low-Peak 600V Class RK1 Fuse | | **Amperage Rating** | 500A | Rated to carry 500 Amps continuously | | **Voltage Rating (AC)** | 600 Vac | Maximum AC voltage | | **Voltage Rating (DC)** | 300 Vdc | Maximum DC voltage | | **Interrupting Rating** | 300kA (RMS Sym) | Ability to stop very high fault currents | | **Protection Type** | Dual-Element | Provides both time-delay and fast response | | **Classification** | Class RK1 | High current limitation (superior to RK5) | --- ## 2. Key Electronic Features ### A. Dual-Element Design This fuse contains two distinct components internally: 1. **Thermal Cutout (Time-Delay):** Provides a "slow" response to temporary overloads (like motor startup currents). It allows the circuit to handle brief surges without blowing the fuse. 2. **Short-Circuit Element (Fast-Acting):** A calibrated link that reacts instantly (less than 0.008 seconds) to massive fault currents (short circuits), protecting sensitive downstream equipment. ### B. Current Limitation As a **Class RK1** fuse, the LPS-RK-500SP is highly current-limiting. In the event of a short circuit, it forces the current to zero before it reaches its first peak. This significantly reduces the **Arc Flash** energy and the mechanical stress placed on busbars and breakers. ### C. Selective Coordination These fuses are designed with a **2:1 coordination ratio**. This means if you have a 500A main fuse and a 250A branch fuse of the same series, only the fuse closest to the fault will blow. This prevents unnecessary "blackouts" in other parts of a facility. --- ## 3. Physical & Material Composition * **Body:** High-grade fiberglass or melamine tube for high arc-containment and physical durability. * **Terminals:** Large knife-blade contacts (typical for 500A fuses) to ensure low resistance and heat dissipation. * **Reject Feature:** The "RK" designation ensures it fits into R-Series fuse blocks, preventing the accidental installation of inferior non-current-limiting fuses (like Class H or K). --- ## 4. Common Applications * **Large Motor Branch Circuits:** Handles high-torque startup currents without nuisance tripping. * **Main Power Feeders:** Used as a main disconnect fuse for industrial buildings. * **Inductive Loads:** Ideal for large transformers where inrush current is a factor.