Methods for the control of large medium-voltage motors: application considerations and guidelines

Starting and control methods available for medium-voltage (MV) induction motors (2.4-7.2 kV) in the petrochemical industry are continually changing in terms of application considerations due to the evolution of available products and changing characteristics of the machine and processes. This paper summarizes several common methods and provides application guidelines for proper choice selection considering the distribution system, driven equipment, speed-torque issues, process requirements, starter method limitations, and economics. Starting means reviewed include MV soft starters, variable-frequency drives, and autotransformer, capacitor, reactor, captive transformer, across-the-line controllers, as well as fluid couplers.