Induction machine design methodology for self-sensing: Balancing saliencies and power conversion properties

Zero to low speed, flux or rotor position self-sensing techniques rely on the interaction of saliencies (asymmetries) with an injected signal or special switching pattern in the inverter to produce a response which contains information about the location of the saliency. In this paper three types of deterministic spatial rotor position saliencies are introduced into an induction machine. The saliencies were created by modulating the 1) rotor bridge opening width, 2) rotor bridge opening height, and 3) rotor bridge opening fill. The influence of saliency geometric design variables on self-sensing and power conversion properties is determined using a design of experiments and response surface methodology. An example induction machine design, which maximizes self-sensing properties while preserving power conversion abilities, is presented. Modulation of the rotor bridge fill appears to be the least desirable saliency type. Both rotor bridge opening width and height modulations can be used successfully but the rotor bridge opening width modulation requires extra simulations to characterize self-sensing properties.