Reserves for Power Saving of Synchronous Motors as a Part of Metallurgical Drives
Evolution of power electronics and microprocessor technology has contributed to the situation when an adjustable electric drive based on synchronous and asynchronous motors has become predominant in metallurgical industry. However, a large number of nonadjustable powerful synchronous motors (SM) are still in operation. With the existing technology of metallurgical industry, most powerful synchronous motors will remain in the near future and the issues of their effective use as energy-intensive consumers as remain relevant and practically significant. The article discusses the unrealized reserves for power saving of powerful SM for rolling production. The paper states the requirements to the automatic excitation control system of synchronous motors of rolling mills; these requirements include provision of stable, rapidly damping character of the transient process during impulse loads and minimization of total electric losses in the stator and in the motor field. The paper considers different options for design of the excitation systems of synchronous motors with a force-measuring transducer as well as excitation by the indirect method, by the signals of the voltage and the current of the converting unit. Assessment of electric energy saving was carried out for operating modes, for on-load operation and for idle running. The practice was justified when the unit with the unmotivated idle operation of the motor during long operational delays of the capital equipment was equipped with soft starters to reduce power losses.