A periodic burst injection method for deriving rotor position in saturated cage-salient induction motors without a shaft encoder

This paper describes a new method for estimating the incremental rotor position for an induction machine without using a shaft sensor. The method assumes a saturated induction motor having an engineered cage saliency spanning one pole pitch. The voltage-source inverter driving the machine is also used to inject a high-frequency signal which is needed to detect position. The paper discusses two ways in which this can be achieved. This method has been proven successful with a loaded machine at low speeds and overcomes problems associated with saturation.