tailieunhanh - Power Electronic Handbook P11

Induction machines have become the staple for electromechanical energy conversion in today’s industry; they are used more often than all other types of motors combined. Several factors have made them the machine of choice for industrial applications vs. DC machines, including their ruggedness, reliability, and low maintenance [1, 2]. The cage-induction machine is simple to manufacture, with no rotor windings or commutator for external rotor connection. There are no brushes to replace because of wear, and no brush arcing. | 11 Control of Induction Machine Drives Daniel Logue University of Illinois at Urbana-Champaign Philip T. Krein University of Illinois at Urbana-Champaign Introduction Scalar Induction Machine Control Vector Control of Induction Machines Vector Formulation of the Induction Machine Induction Machine Dynamic Model Field-Oriented Control of the Induction Machine Direct Torque Control of the Induction Machine Summary Introduction Induction machines have become the staple for electromechanical energy conversion in today s industry they are used more often than all other types of motors combined. Several factors have made them the machine of choice for industrial applications vs. DC machines including their ruggedness reliability and low maintenance 1 2 . The cage-induction machine is simple to manufacture with no rotor windings or commutator for external rotor connection. There are no brushes to replace because of wear and no brush arcing to prevent the machine from being used in volatile environments. The induction machine has a higher power density greater maximum speed and lower rotor inertia than the DC machine. The induction machine has one significant disadvantage with regard to torque control as compared with the DC machine. The torque production of a given machine is related to the cross-product of the stator and rotor flux-linkage vectors 3-5 . If the rotor and stator flux linkages are held orthogonal to one another the electrical torque of the machine can be controlled by adjusting either the rotor or stator flux-linkage and holding the other constant. The field and armature windings in a DC machine are held orthogonal by a mechanical commutator making torque control relatively simple. With an induction machine the stator and rotor windings are not fixed orthogonal to one another. The induction machine is singly excited with the rotor field induced by the stator field further complicating torque control. Until a few years ago the .