SCR power controllers or silicon controlled rectifier power controllers precisely regulate output power to resistive heating loads such as industrial furnaces and ovens. They can be interfaced with computers and software that can monitor and/or control power throughput. The two primary modes of SCR control are: Phase Angle: Controller allows partial waveform through during every half-wave cycle. Zero-Crossing: Controller allows proportion of complete half-waves through to regulate power.
Important operating specifications for SCR power controllers include the phase, operating voltage, and maximum current. Phase choices for SCR power controllers include single phase, three phase 2-leg, and three phase 3-leg. Operating voltages for SCR power controllers include <100 VAC, 100-199 VAC, 200-299 VAC, 300-399 VAC, 400-499 VAC, and > 500 VAC. The maximum current is the maximum rated current of the SCR power controller.
Operating features to consider when specifying SCR power controllers include command signals, control feedback, diagnostic indicators, soft start, and failure detection or alarm. Command signal choices include analog voltage, analog current, and potentiometers. With an analog voltage command signal the output of the controller is regulated by varying an analog input voltage signal. With an analog current command signal the output of controller is regulated by varying an analog input current signal. The output of controller can be regulated by varying a potentiometer, often in the form of a dial on the front panel. Control feedback choices are voltage, current, or power. Diagnostic indicators are visual indicators during ON condition (needles, LEDs, etc.) A soft start provides for a gradual ramp-up of output for load protection. Failure detection or alarm uses circuitry that detects failures such as short circuits or missing cycles and provides interlock signal or audible alarm.
Mounting choices for SCR power controllers include open panel, enclosed wall mount, rack mount, DIN rail, and freestanding or cabinet. Open panel SCR power controllers are wall-mounted with open, accessible electrical components. In an enclosed wall mount an enclosure is provided along with mounting holes on the enclosure. A rack mount unit is designed to be mounted in a rack assembly. A DIN rail mounted unit is designed for mounting on a standard DIN Rail. Freestanding or cabinet units stand on the floor or are integrally mounted in the cabinet. An important environmental operating parameter to consider when specifying SCR power controllers is operating temperature.