## Technical Overview: ST700C..L Series Phase Control Thyristor The **ST700C..L** series (where ".." represents the voltage rating) consists of high-power, hockey-puck style **Phase Control Thyristors (SCRs)**. These are manufactured by brands like Vishay (formerly International Rectifier) and are designed for heavy-duty industrial applications requiring precise switching of high currents. --- ### 1. Key Technical Specifications | Parameter | Symbol | Typical Value | | :--- | :--- | :--- | | **Max Average On-State Current** | $I_{T(AV)}$ | 700 A (@ $T_C = 55^\circ C$) | | **Voltage Range ($V_{DRM}/V_{RRM}$)** | $V_{RRM}$ | 800V to 2000V | | **Max RMS Current** | $I_{T(RMS)}$ | 1345 A | | **Max Peak Surge Current** | $I_{TSM}$ | 9150 A (@ 50Hz) | | **Gate Trigger Voltage** | $V_{GT}$ | 3.0 V | | **Package Type** | Case Style | B-PUK (TO-200AB) | --- ### 2. Physical Design and Packaging The "L" in the suffix typically refers to the specific package lead/terminal style or height. These devices utilize a **"Hockey Puck"** press-pack design: * **Double-Sided Cooling:** The flat ceramic surfaces allow for heat dissipation from both the anode and cathode sides when clamped between heatsinks. * **Pressure Contact:** Unlike soldered components, these require a specific **clamping force** (typically 11kN to 24kN) to ensure electrical conductivity and thermal management. * **Hermetic Seal:** The ceramic-to-metal seal protects the internal silicon wafer from humidity and contaminants. --- ### 3. Functional Operation The ST700C is a **Phase Control Thyristor**, meaning it is optimized for low-frequency switching (50Hz to 60Hz) where the "turn-on" point is delayed to control the average power delivered to a load. * **Triggering:** It remains in a non-conducting state until a pulse is applied to the Gate. * **Commutation:** It only stops conducting (turns off) when the current flowing through it drops below the "holding current" threshold, usually during a natural AC zero-crossing. --- ### 4. Typical Applications The ST700C..L series is commonly found in the following systems: 1. **DC Motor Drives:** Controlling the speed of large industrial motors. 2. **AC Soft Starters:** Reducing inrush current in heavy machinery. 3. **Welding Equipment:** High-current power supplies for industrial welding. 4. **Electrochemical Processes:** Used in large-scale rectifiers for plating or electrolysis. 5. **Induction Heating:** Power stages for melting or hardening metals. --- ### 5. Identification Code Example `ST700C12L0L` * **ST:** Thyristor * **700:** Average Current (700A) * **C:** Ceramic Puk * **12:** Voltage rating (1200V) * **L:** Lead type/Standard gate version