The Wattcor W312 thyristor power controllers are designed to manage various load types, including:
- Standard resistive loads with low temperature coefficients,
- Short-wave infrared heaters,
- Inductive loads such as transformer primaries.

Typical applications include:

• Single-phase operation: load and controller connected between two phases or between one phase and neutral.
• Three-phase operation: three W312 units connected in open-delta or star configuration with neutral.

The W312 series is built on a common architecture and is available in five different current ratings for operation at 50 °C ambient temperature. The power circuit supports a wide voltage range from 24Vac up to 660Vac (maximum range 20…725Vac). These controllers operate using phase angle firing, slicing individual half-waves of the AC supply to control load power.
The conduction angle is proportional to the analog control signal, allowing power adjustment from 0 to 100%. Voltage signals (0…5V or 0…10V) or current signals (0/4…20 mA) are typically provided by a temperature controller or a potentiometer for manual adjustment.

Phase angle switching ensures precise power control and fast response, enabling the soft-start function. The soft-start gradually ramps the conduction angle from zero up to the value dictated by the control input, which is essential for resistive loads with low cold resistance (e.g., tungsten, molybdenum disilicide, Kanthal Super).
A logic input can inhibit the controller, interrupting power delivery even when a command signal is present.
Front-panel LED indicators provide information on the auxiliary electronics supply and the conduction status of the controller.

The W312 series is designed for rated performance at 50 °C, with a working range from -5 °C to 60 °C. Signal connections use plug-in connectors for easy installation, and units can be mounted on a DIN rail or directly on a front panel.