The **S2-621-R** is a specific electronic component, most commonly identified as a **Radial Lead Metal Oxide Varistor (MOV)** manufactured by **SEW** or similar protection-device specialists. It is designed to protect electronic circuits against voltage surges and spikes. --- ### 1. General Specifications The S2-621-R belongs to a category of "Transient Voltage Suppressors." Below are the typical technical parameters for this part number: | Parameter | Specification | | :--- | :--- | | **Component Type** | Metal Oxide Varistor (MOV) | | **Varistor Voltage** | 620V (Nominal) | | **Tolerance** | ±10% | | **Clamping Voltage** | ~1025V (at standard pulse current) | | **Maximum AC Voltage** | 385V RMS | | **Maximum DC Voltage** | 505V | | **Lead Style** | Radial Lead (Through-hole) | | **Body Diameter** | Usually 14mm or 20mm (indicated by the series prefix) | --- ### 2. Physical Construction The device is constructed from a ceramic mass of **Zinc Oxide (ZnO)** grains mixed with other metal oxides. * **Encapsulation:** Coated in a flame-retardant epoxy resin (usually blue or red). * **Leads:** Two tinned copper wires for through-hole PCB mounting. * **RoHS Compliance:** The "-R" suffix typically denotes that the part is **RoHS Compliant** (Lead-free). --- ### 3. Functional Operation The S2-621-R acts as a **voltage-dependent resistor**. Its behavior can be summarized by its non-linear resistance: 1. **High Resistance (Normal State):** When the circuit voltage is below 385V AC, the varistor has very high resistance and acts as an open circuit, drawing negligible current. 2. **Low Resistance (Surge State):** When a high-voltage spike (e.g., lightning or inductive switching) exceeds 620V, the varistor's resistance drops instantly. 3. **Shunting:** The excess current is shunted through the varistor, protecting sensitive downstream components from the overvoltage. --- ### 4. Common Applications Due to its 620V rating, this part is frequently used in power supply protection for 220V/230V AC mains: * **Power Strips:** To provide surge protection for home electronics. * **Switch Mode Power Supplies (SMPS):** Placed at the AC input stage. * **Industrial Controllers:** Protecting PLCs and relays from inductive kickback. * **Motor Protection:** Absorbing transients generated during motor startup/shutdown. --- ### 5. Identification Schematic In a circuit diagram, the S2-621-R is represented by the following symbol: ```text | / \ | V | <-- Varistor Symbol (often labeled MOV or RV) \ / | ```