Estimation of Torque Sharing for Industrial Dual Induction Motor Drives under Special Current Sensor Configuration

Industrial electronic control units used in three-phase single-motor AC drives typically present three input channels conceived to read the stator current vector. Usually, two current sensors are placed at the inverter output and serve to compute a motor torque and flux upon which drive is controlled. However, to increase interchangeability, control units are utilised indistinctly for the control of single-motor and parallel-connected multi-motor drives. When multiple motors are supplied by a single inverter, the current sensors deliver the sum of the phase stator current of all motors. If load imbalances arise, drive might go under asymmetrical heating, producing imprecise torque and worsening dynamic response. Specially under load imbalances, it is useful to know the torque sharing, since it can be used to enhance drive performance. In this paper, the torque sharing of dual induction motors is computed under a special current sensor configuration that uses three current sensors. A comparison of several signal processing schemes is presented. Experimental results measured on a dual induction motor test bench show the ability and precision of the proposed schemes to compute the torque and flux of each individual motor.