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The Sustainable Automation SLC-HW series Secondary Load Controller is a highly engineered fast-response power controller designed for use with electric hot water boilers. It is specifically designed for wind-diesel and mini-hydro power systems where there is a need for diesel load control and/or system frequency control. The system is an evolution of the highly successful secondary load controllers used in the Wales High Penetration Wind-Diesel Project implemented by the U.S. Department of Energy’s National Renewable Energy Laboratory.
Element switching is accomplished using thyristor solid-state relays (SSR) of the zero-switching type. Thus, all SSR switching is done at zero voltage, which eliminates the current waveform distortion and the poor power factor associated with phase-controlled SCR power controllers. All of the thyristors are directly bonded to integral heat sinks conservatively rated to handle their respective electrical loading. By switching on various combinations of the heating elements, any power level from zero to full load may be achieved, with a resolution of 1% to 4% of full load, depending on the model. Element switching is updated up to 50 times/second, allowing for smooth continuous control of electric power.