High Performance IM Drive by Coordinate Control Using a Controlled Current Inverter

An induction motor drive which can replace a high performance dc motor drive in steel and paper mill applications has long been desired. The authors have brought this into reality by accurate coordinate control of a combination of a caged rotor induction motor and controlled current inverter. The concept of the improved coordinate control is that the exciting current and torque current are controlled independently by controlling slip and stator current vector. This is achieved by a coordinate transformation of the electrical quantities of an induction motor. A generalized coordinate control system and a method of compensating for variations in flux and torque resulting from a difference between actual constants and controller constants are described.