Application considerations for operating VSI-FED MV motors in hazardous locations

Determining the suitability of a medium-voltage motor which will be installed within a hazardous location as outlined in IEEE 1349, powered by a multi-level, voltage source, adjustable speed drive that is not isolated by a phase-shifting transformer requires two key items to be investigated - thermal heating due to the current harmonics, and the energy contained in uncontrolled sparking from the motor shaft to ground. This paper reviews the process that was used for a possible application of a drive with a motor in a Class I, Division 2 environment, along with modifications that were made to the design and operation of the drive to meet the stated requirements.