Heat and Harmonics: Solutions to Concerns in Air-Cooled Medium-Voltage Adjustable-Speed Drives

Scholarly publications exist on several aspects of adjustable-speed drives (ASDs). Their application considerations, benefits, specifications, and operation are well understood. Medium-voltage (MV) drives have been applied not only to upstream, midstream, and downstream industries of the oil and gas value chain but also in other industries such as pulp and paper, cement, water and waste water, power generation, and test stands. This has been possible because of reliable high capacity power semiconductor devices. Heat loss is a major contributor to the lifecycle cost of an installation of MV drives. This is not understood initially but becomes significant when assessed over a 25-year life span. Air-cooled drives are specified at large horsepower ratings or in places with high or low ambient temperatures without fully understanding the long-term impact to reliability, safety, and running costs. On another note, line-side harmonics is also of concern not only to the power delivery apparatus of an operator's plant but also to the utility providers. IEEE Standard 519-1992, which was revised in 2014, is often specified for MV drives, but the application and understanding of the standard are inconsistent among industry participants. This article addresses the foregoing two issues. First, it describes conventional and nonconventional methods for managing heat that the industry has developed and will cover application considerations when specifying, evaluating, procuring, and installing those solutions. The final part of the article reviews IEEE Standard 519-2014 and how it is applied in the context of an MV drive. Further, the article briefly touches online-side harmonic mitigation techniques that are employed and how to specify them to best avoid issues. Guideline for practicing engineers to familiarize themselves with the heat and harmonic issues of MV drives and how to tackle them successfully are also covered in this article.