Energy efficiency of an induction motor operating in a powertrain of an electric vehicle

Introduction. When employing induction motors in powertrains of electric vehicles, one should take into account their energy efficiency, since a capacity of energy storage systems used in electric vehicles is limited. This implies choosing an electric drive control technique that satisfies criteria of both dynamic performance and minimum energy losses. This work describes an analysis of induction motor energy efficiency when considering two control techniques, namely the constant magnetic flux control (also known as the field-oriented control) and the constant slip control.

The purpose of the study is to assess the energy efficiency of an induction motor when it operates in a powertrain of an electric vehicle.

Methodology and research methods. Numerical investigation was conducted by means of electrodynamic equations describing a steady-state operation of the induction motor. A measure to compare energy efficiencies of the considered control techniques was introduced in the form of a quotient of the efficiency factors provided by these techniques and calculated for different values of the electromagnetic torque and the rotor’s frequency.

Scientific novelty and results. A method is proposed, which allows for an analysis of induction motors in respect of the energy efficiency provided by the constant magnetic flux control and the constant slip control, based on a quotient of the calculated efficiency factors. Furthermore, a connection is revealed between the electromagnetic torque exerted by the stator current and the power losses in the motor. The work justifies the selection criteria for the control technique and essential design parameters of an induction motor intended for an electric traction drive of a vehicle.

The practical significance of the work is constituted by the recommendations given on the selection of a control technique and design features of an induction motor taking into account its energy efficiency.

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