Heat & Harmonics - the Most Significant Concerns in Air-Cooled Medium Voltage Adjustable Speed Drives & What to Do about It?

Scholarly publications exist about several aspects of adjustable speed drives. 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 & gas value chain, but also in other industries such as pulp & paper, cement, water/wastewater, power generation and test stands. This has been possible by reliable high capacity power semiconductor devices. Heat loss is a major contributor to the life cycle 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 519-1992 which was revised in 2014 is often specified for MV drives, but application and understanding of the standard is inconsistent among industry participants. This paper addresses the foregoing two issues. The manuscript first describes conventional and non-conventional methods for managing heat that the industry has developed over a period and will cover application considerations when specifying, evaluating, procuring and installing those solutions. The final part of the paper reviews the IEEE 519-2014 standard and how it is applied in the context of a MV drive. Further, the paper briefly touches on line-side harmonic mitigation techniques that are employed and how to specify them to best avoid issues. This paper serves as a guideline to the practicing engineer to familiarize themselves with the heat and harmonic issues of MV drives and how to be successful in tackling them.