The **FTR-K3JB012W-NIL** is a high-power, high-reliability PCB-mounted power relay manufactured by **Fujitsu** (or Takamisawa). It is specifically designed for high-inrush applications such as power supplies, motor controls, and industrial automation. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Relay Series** | FTR-K3 | | **Contact Form** | 1 Form A (SPST-NO) | | **Coil Voltage** | 12V DC | | **Rated Contact Current** | 20A / 25A (Application dependent) | | **Max Switching Voltage** | 250V AC / 30V DC | | **Inrush Current Capability** | High (Up to 78A or 100A depending on variant) | | **Dielectric Strength** | 5,000V AC (between coil and contacts) | | **Surge Strength** | 8,500V | | **Mounting Type** | Through-hole (PCB) | --- ### 2. Functional Breakdown #### A. Contact Material and Structure The FTR-K3 series utilizes specialized contact materials (often Silver Tin Oxide - AgSnO2) to handle high peak currents. The **"JB"** designation typically refers to a heavy-duty contact structure designed to withstand the heat generated by 20A+ loads without welding the contacts together. #### B. Coil Characteristics The **"012W"** indicates a nominal coil voltage of **12V DC**. The "W" usually signifies a standard sensitivity coil (approx. 780mW - 900mW power consumption). This requires a driver circuit (like a transistor or Darlington pair) since most microcontrollers cannot output enough current to drive the coil directly. #### C. Safety and Isolation This component is designed with high safety standards in mind: - **Creepage and Clearance:** It maintains a large physical distance between the low-voltage coil side and the high-voltage contact side. - **Flammability:** The plastic housing is generally rated UL94V-0 (self-extinguishing). --- ### 3. Application Use Cases Due to its high current rating and robust insulation, it is commonly found in: * **HVAC Systems:** Controlling compressors or heaters. * **EV Charging:** Low-level AC charging control. * **Power Strips:** Smart plugs and industrial surge protectors. * **White Goods:** Washing machines and dishwashers for motor/heater switching. --- ### 4. Circuit Diagram Reference (Typical) To use this relay in a digital circuit, a flyback diode is essential to protect the driving electronics. ```cpp [MCU Pin] ---> [1k Resistor] ---> [NPN Base] | [Collector] <--- [Relay Coil Pin 1] | | | [Flyback Diode] | | [Emitter] [12V VCC] | [GND] ```