Control Scheme for Open-Ended Induction Motor Drives With a Floating Capacitor Bridge Over a Wide Speed Range

An electric drive for high-speed applications is analyzed in this paper. The drive consists of a dual two-level inverter with a floating bridge, fed by a single voltage source, and a three-phase induction motor with open-ended stator windings. The floating bridge compensates the reactive power of the motor, so that the main inverter operates at unity power factor and fully exploits its current capability. The constant power speed range of the motor can be significantly extended depending on the dc-link voltage of the floating inverter. The details of the control system are examined and the feasibility of an electric drive is experimentally assessed.