Standstill Flux Linkage Measurement using Pulse Amplitude Modulated Current Injection towards Characterization of Interior Permanent Magnet Machines

This paper presents an experimental method for extraction of Direct (D) and Quadrature (Q) axis flux linkages of an Interior Permanent Magnet Synchronous Machine (IPMSM). The method considers both saturation and cross-magnetization effects over the entire range of the machine's rated current in both DQ axes. The flux-linkage characteristics are computed by exciting the stator windings through a series of current pulse injections via a switching converter using a closed-loop current regulator operating in a Field Oriented Control (FOC) scheme in the DQ frame. A novel method for generating the current pulse pattern is proposed which enables automatic creation of 2D Flux Linkage maps of the motor using any standard controller. The method takes advantage of standard measurements available in an industrial drive such as DC-link voltage, phase current, phase voltage and shaft position thus enabling the wide usage of the technique on industrial equipment for high-efficiency motor control algorithms. The proposed method in this paper achieves near standstill condition of any given test motor during pulse injections which enable experiments without the need for custom test rigs or isolation of motor from the shaft implements. Experimental results were taken on a 3HP IPMSM motor to validate the effectiveness of the proposed method.