Pumps & Systems, Jun. 2014, by Mark W. Harshman.
http://www.pump-zone.com/motors/june-2014-determine-total-cost-ownership-when-selecting-medium-voltage-drives

"Part One of this two-part series (Pumps & Systems, May 2014) explained how factors other than initial purchase price work together to generate the total cost of ownership (TCO) for medium-voltage variable frequency drives (VFDs). Part Two discusses what creates high reliability in a medium-voltage VFD."