### KTK-R-3/4 Fuse Overview The **KTK-R-3/4** is a high-performance, fast-acting supplemental fuse part of the **Limitron™** series, manufactured primarily by Eaton (Bussmann Division). It is specifically designed to provide high current-limiting capabilities in a compact physical size. --- ### Technical Specifications | Feature | Specification | | :--- | :--- | | **Part Number** | KTK-R-3/4 | | **Amperage Rating** | 0.75 Amps (3/4 A) | | **Voltage Rating (AC)** | 600 Vac | | **Interrupting Rating** | 200,000 Amps RMS Symmetrical | | **Fuse Class** | Class CC | | **Response Time** | Fast-Acting | | **Material** | Melamine tube with nickel-plated brass endcaps | | **Dimensions** | 13/32" x 1-1/2" (10.3mm x 38.1mm) | --- ### Key Features and Construction 1. **Class CC Rejection Feature:** The "R" in the part number signifies a **rejection tip**. This physical notch prevents the installation of lower-rated fuses (like standard KTK midget fuses) into Class CC fuse holders, ensuring the safety of the circuit is maintained. 2. **Current Limitation:** This fuse is highly current-limiting. In the event of a short circuit, it reacts within milliseconds to "limit" the peak energy that passes through, protecting sensitive downstream components. 3. **Melamine Body:** The body is constructed from melamine, which provides excellent dimensional stability and high arc-suppression capabilities compared to standard glass fuses. --- ### Common Applications The KTK-R-3/4 is typically used in industrial and commercial settings where high-voltage protection is required in a small footprint: * **Control Transformer Protection:** Ideal for protecting the primary side of control transformers. * **Lighting Circuitry:** Used in specialized lighting ballasts and circuits. * **General Purpose Circuits:** Used in any 600V or less application requiring fast-acting protection without a time-delay requirement. * **HVAC Systems:** Often found in industrial heating and cooling control panels. --- ### Comparison: KTK-R vs. KTK (Non-R) | Feature | KTK-R (Class CC) | KTK (Midget) | | :--- | :--- | :--- | | **Rejection Tip** | Yes | No | | **Interrupting Rating** | 200kA | 100kA | | **UL Listing** | Branch Circuit Protection | Supplemental Protection | | **Primary Use** | Safety-critical branch circuits | General supplemental use |