Transient Energy Efficiency Analysis of Field Oriented Induction Machines

An open loop control law for stator d- and q-axis currents in a rotor field oriented induction machine are derived in the form of analytical functions of time and used to study how energy losses during speed transients can be minimized. The trajectories due to the developed functions are inspired by the numerical solution of the induction machine optimal control problem. It is found that transient energy efficiency of the machine depends primarily on the initial rotor flux at the beginning of the transient interval. The influences of change in the rotor speed, rotor moment of inertia, and rotor time constant on optimal transient energy efficiency are analyzed and results are discussed.