By Bobby Houston, Pat Lemmon, and James K. Martin, Intermountain Electronics

This presentation will discuss the issues that one will have to consider when installing variable frequency drives (VFDs) in coal mining applications. One issue for consideration involves the performance of the ground fault protection devices when applied with a VFD operating at various speeds. As VFDs have become more commonplace in longwall applications, considering some equipment is evaluated for approval as “permissible” equipment, the rigors of testing the real world application will require a documented successful test result. The requirements one must meet for acceptability of a VFD application as “permissible” has merit and should be considered regardless of whether the installation requires an approval for permissibility.