The **VDR10D561KJ** is a specific model of a **Voltage Dependent Resistor**, more commonly known as a **Metal Oxide Varistor (MOV)**. Its primary function is to protect electronic circuits from high-voltage surges and transients. --- ## 1. Technical Specifications The part number follows a standard industry naming convention. Here is the breakdown of its core parameters: | Parameter | Specification | Description | | :--- | :--- | :--- | | **Varistor Voltage** | 560V | The voltage at which the device begins to conduct (typically measured at 1mA DC). | | **Tolerance** | ±10% (K) | The allowable variation in the rated varistor voltage. | | **Disk Size** | 10mm (10D) | The physical diameter of the ceramic disk (affects energy handling). | | **Maximum AC Voltage** | 350V RMS | The highest continuous AC voltage it can handle without triggering. | | **Maximum DC Voltage** | 450V DC | The highest continuous DC voltage it can handle. | | **Energy Rating** | ~70-90 Joules | The amount of transient energy it can dissipate. | --- ## 2. Key Features * **Non-linear Resistance:** At normal voltages, the VDR has very high resistance (acting as an open circuit). When a voltage spike occurs, the resistance drops instantly, shunting the current to ground. * **Fast Response Time:** These devices react in nanoseconds ($<25ns$), making them ideal for protecting sensitive semiconductors. * **Bi-directional:** It protects against both positive and negative voltage spikes. * **Compact Form Factor:** The "10D" (10mm) size provides a balance between PCB space and surge current capability (usually around 2,500 Amps peak). --- ## 3. Circuit Application In most designs, the VDR is placed **in parallel** with the AC input line. ```circuit [ AC Line ] ----+---- [ Fuse ] ----+---- [ Load ] | | [VDR] [VDR] <-- Protects Load | | [ Neutral ] ----+------------------+---- ``` ### Common Uses: 1. **Power Supplies:** Protecting SMPS (Switch Mode Power Supplies) from lightning strikes or grid switching. 2. **Home Appliances:** Used in washing machines, refrigerators, and TVs. 3. **Industrial Equipment:** Protecting PLC inputs and motor controllers. --- ## 4. Safety Considerations * **Failure Mode:** VDRs degrade over time with each surge they absorb. When they fail permanently, they often short-circuit. * **Requirement for Fuse:** Because a failed VDR can cause a short, it **must** be used in conjunction with a thermal fuse or a standard circuit breaker to prevent fire hazards.