SCR Power Thermal Systems
Temperature regulation is required in nearly every manufacturing process, typically for the purposes of material heating, melting, drying, or forming. SCR power controllers, also called silicon controlled rectifiers (SCRs), play a critical role in temperature regulation. Their primary use is to control the flow of electricity from the grid to a heater. This function precisely regulates temperature to produce specific material effects or properties within an industrial furnace, oven, or other thermal processing equipment. Compared to alternative devices, such as IGBT-based controllers, SCR power controllers provide much greater efficiency—up to 99.5%. SCR power controllers also are used to replace contactors or relays due to the wear-free switching offered by thyristor devices. This characteristic greatly improves reliability and product longevity.
SCR Power Thermal System Accuracy and Repeatability
Variations in mains voltage and heating-element resistance are common issues that impair the accuracy of temperature regulation. The mains voltage can vary up to and even beyond ±10%, resulting in temperature fluctuations. SCR power controllers compensate for mains voltage fluctuations by employing RMS voltage regulation. An SCR’s voltage regulation mode adjusts the firing angle (phase angle) or duty cycle (zero cross) of the SCR output to maintain a constant voltage output proportional to the set point. Variations in heating-element resistance are due to aging, temperature coefficients, and/or other materials characteristics. SCR power controllers can compensate for these variations by regulating the RMS output current. When both true RMS current and true RMS voltage regulation are employed, the SCR power controller is said to be in power regulation mode. Power regulation allows the SCR power controller to regulate true power independent of variations in the mains voltage or heater resistance. Power regulation is the most accurate means of regulating temperature and promotes the highest level of process repeatability.
SCR Power Thermal System Energy Efficiency
Both the public and industrial sectors have seen a dramatic increase in energy costs in recent years. The latest production technologies offer high efficiency to reduce overall capital and operating expenditures, especially in energy-intensive applications. At 99.5% efficiency, SCR power controllers offer a distinct advantage over alternative devices such as IGBT-based power supplies and converters. Furthermore, modern SCR power controllers offer multiple firing modes, enabling users to select the best control method for their application. Firing modes can be selected based on technical requirements, such as minimizing THD or maximizing power resolution. Advanced control methodologies such as mains load optimization can be used to reduce peak load demand of multiple SCR units, resulting in lower energy rates.
The inherent efficiency of SCR power controller technology also offers specific cost advantages. At 99.5% efficiency, SCR power controllers save energy simply due to their extremely low power losses (heat load) compared to switch-mode power supplies. The low loss designs can operate in ambient temperatures up to 55°C (131°F) (using de-rated SCRs), reducing the need for air conditioning and other associated costs. Furthermore, many utilities charge a penalty if a certain power factor, typically 0.9, is not met. SCR power controllers with MoSi, VT, zero cross/TAKT (transformer or direct loads), mains load optimization, or other digital features can save thousands of dollars annually in energy costs by improving power factor and reducing peak kVA.
GET designs and manufactures complete thermal systems to include the heaters, temperature sensors, controllers and all of the components of a thermal system. Designing and manufacturing the complete thermal system allows GET to recommend, develop and deliver the optimum thermal solution for our customers’ equipment and process heat requirements. GET manufactures thermal systems for a broad range of industries including but not limited to: semiconductor processing, photovoltaic, aerospace, analytical instrumentation, medical equipment, packaging, foodservice equipment and plastics processing. GET customers receive the highest level of technical engineering combined with exceptional customer service.
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