### Overview of the FNQ-R Series The **FNQ-R** is a specific type of industrial fuse within the **Bussmann (Eaton)** family. It is categorized as a **Class CC** current-limiting, time-delay fuse. These are widely used in electrical circuits to protect sensitive electronic components, particularly control transformers and circuits with high inrush currents. --- ### Key Technical Specifications | Feature | Specification Details | | :--- | :--- | | **Class** | Class CC | | **Voltage Rating** | 600 Vac (or less), 300 Vdc (varies by amp) | | **Amperage Range** | 1/4A to 30A | | **Interrupting Rating** | 200,000A RMS Symmetrical (at 600 Vac) | | **Physical Size** | 13/32” x 1-1/2” (10.3mm x 38.1mm) | | **Standard Compliance** | UL Listed (248-4), CSA Certified | --- ### Electronic Characteristics & Internal Design #### 1. Time-Delay Mechanism The FNQ-R is a "slow-blow" or **Time-Delay** fuse. * **Purpose:** It allows for brief surges (inrush current) without blowing. * **Application:** When a motor or transformer starts, it draws much more current than its steady-state operation. The FNQ-R's internal thermal element absorbs this heat temporarily, preventing "nuisance tripping." #### 2. Current Limitation Despite being a time-delay fuse, it is **Current-Limiting**. * In the event of a catastrophic short circuit, the fuse reacts extremely fast (within less than half a cycle) to physically open the circuit. * This limits the peak let-through current, protecting downstream components like contactors and solid-state relays from melting or exploding. #### 3. Rejection Feature The "R" in FNQ-R stands for **Rejection**. * The fuse has a unique physical groove on one end. * This prevents a user from accidentally replacing a high-performance Class CC fuse with a standard midget fuse (like an FNQ) that lacks the same interrupting capacity. --- ### Common Applications The FNQ-R is the "gold standard" for the following electronic environments: * **Control Transformers:** Specifically designed to handle the high inrush currents of transformer primary protection. * **Solenoids:** Protects the coils from overheating without tripping during activation. * **Motor Control Circuits:** Used in branch circuit protection where space is limited. --- ### Comparison: FNQ vs. FNQ-R | Feature | FNQ (Midget) | FNQ-R (Class CC) | | :--- | :--- | :--- | | **Rejection Tip** | No | Yes | | **Interrupting Rating** | 10,000A | 200,000A | | **Safety Level** | Standard | High (Branch Circuit Rated) |