## Overview of KTK-R Fuses The **KTK-R** is a specific series of fast-acting, supplemental fuses designed primarily for control circuits and motor branch circuit protection. They belong to the **Class CC** family of fuses, which are known for their compact size and high rejection capabilities. --- ### 1. Key Technical Specifications The electrical characteristics of KTK-R fuses are standardized to ensure safety in industrial environments. | Feature | Specification | | :--- | :--- | | **Class** | Class CC | | **Voltage Rating** | 600 Vac (Standard) | | **Interrupting Rating** | 200,000 Amps RMS Symmetrical | | **Current Range** | 1/10A to 30A | | **Speed** | Fast-Acting | | **Material** | Melamine tube with nickel-plated bronze endcaps | --- ### 2. Design and Physical Construction The "R" in KTK-R stands for **Rejection**. This is a critical safety feature in electronic and electrical systems. * **Rejection Tip:** Unlike standard midget fuses (like the KTK series), the KTK-R has a unique physical grooved endcap. This prevents the installation of a fuse with a lower interrupting rating into a Class CC fuse holder. * **Compact Dimensions:** They typically measure **13/32" x 1-1/2"** (approx. 10mm x 38mm). * **Melamine Housing:** Provides high resistance to heat and prevents the body from shattering under high-fault conditions. --- ### 3. Electronic Applications KTK-R fuses are strategically used in systems where space is limited but high fault current protection is required. #### A. Control Transformer Protection They are widely used to protect the primary side of control transformers. Because they are fast-acting, they respond quickly to short circuits, preventing damage to sensitive downstream electronic components. #### B. Motor Branch Circuits While they are fast-acting, they are often used in specialized motor branch circuits where high-speed clearing is necessary to protect solid-state components. #### C. Industrial Control Panels (UL 508A) Due to their **200kA interrupting rating**, they allow control panels to achieve a high Short-Circuit Current Rating (SCCR), which is often a requirement for industrial safety compliance. --- ### 4. Comparison: KTK vs. KTK-R | Feature | KTK (Standard Midget) | KTK-R (Class CC) | | :--- | :--- | :--- | | **Physical Tip** | Flat / Smooth | Grooved (Rejection Tip) | | **Branch Circuit Use** | No (Supplemental only) | Yes (Branch circuit rated) | | **Safety Level** | Moderate | High (Prevents mismatching) | ---