The **KTK-R-3-1/2** is a specific type of industrial fuse manufactured by companies like Eaton (Bussmann Series) or Littelfuse. It is part of the **Limitron™** family and is designed for high-performance protection in electrical circuits. --- ### 1. Technical Specifications The model name is alphanumeric, where "KTK-R" signifies the series/class and "3-1/2" signifies the amperage rating. | Feature | Specification | | :--- | :--- | | **Current Rating** | 3.5 Amperes (3-1/2 A) | | **Voltage Rating (AC)** | 600 Vac | | **Interrupting Rating** | 200,000 Amps RMS Symmetrical | | **Fuse Class** | Class CC | | **Response Characteristic** | Fast-Acting | | **Material** | Melamine tube with Nickel-plated brass endcaps | | **Dimensions** | 13/32" x 1-1/2" (10.3mm x 38.1mm) | --- ### 2. Key Features #### A. Rejection Feature (The "R" in KTK-R) The "R" indicates that this is a **rejection-type** fuse. It features a unique physical groove on one of the endcaps. This prevents the installation of lower-rated or non-rejection fuses into a Class CC fuse holder, ensuring that the circuit remains protected by the correct safety standards. #### B. Fast-Acting Response Unlike "Time-Delay" fuses, fast-acting fuses are designed to open very quickly (typically within milliseconds) when an overload or short circuit occurs. This is critical for protecting sensitive electronic components that cannot withstand prolonged surges. #### C. High Interrupting Rating With a 200kA interrupting rating, this fuse can safely handle extremely high fault currents without exploding or arcing, which is a vital safety requirement for industrial control panels. --- ### 3. Common Applications The KTK-R-3-1/2 is typically found in the following environments: * **Control Transformer Protection:** Protecting the primary side of transformers. * **Lighting Circuits:** General-purpose branch circuit protection. * **Motor Control:** Used in circuits where motor starting surges are minimal. * **Industrial Control Panels (UL 508A):** Required for branch circuit protection in standardized panels. --- ### 4. Comparison: KTK vs. KTK-R It is important not to confuse the standard KTK with the KTK-R: | Feature | KTK | KTK-R | | :--- | :--- | :--- | | **Class** | Supplemental | Class CC (Branch Circuit) | | **Rejection Tip** | No | Yes | | **Safety Standard** | UL 248-14 | UL 248-4 | | **Interchangeability** | Fits standard holders | Only fits Class CC holders |