INCREASING THE DYNAMIC TORQUE PER AMPERE CAPABILITY OF INDUCTION MACHINES

The objective of this paper is to present a novel means of increasing the dynamic torque per ampere capability of induction machines. The me thod developed is based on use of an indirect field oriented controlle r (IFOC) for the induction machine. It is well known that IFOC allows the rotor flux amplitude to be controlled by the d-axis component of s tator current. It is also well established that the flux-producing com ponent of the stator current may be controlled independent of the torq ue-producing component of the stator current. The principal constraint , however, is that the amplitude of the peak current (the vector ampli tude) is limited by the power electronic switch ratings. This constrai nt implies that optimal partitioning of the current components should be possible. Previously used methods have optimized steady state effic iency or steady state torque per ampere. This paper identifies a dynam ic method which achieves transient torques over 35% greater than the p rior methods. The limitations of the method and its sensitivity to det uning is also examined.