In this paper, the quantitative relationship between the stator flux linkage, torque, and eurrentchanges has been derived via the small-signal analysis technique. Two methods based on active flux and torque injection have been proposed to identify the stator resistance of DTC IMs, which is then utilized for stator temperature estimation. These methods can be implemented in commercial IM drive systems, so as to enhance the thermal monitoring capability and improve the flux control performance These methods are also noninvasive because they eliminate the need for thermocouples, do not require any hardware changes to existing drive systems, and have minimal impacts on the machines' normal operation