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

Starting and control methods available for medium voltage induction motors, (2.4 kV-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 selection considering the distribution system, driven equipment, speed-torque issues, process requirements, starter method limitations and economics. Starting means reviewed include medium voltage soft starters, variable frequency drives, and autotransformer, capacitor, reactor, captive transformer, across the line controllers as well as fluid couplers.