Electromagnetic interference (EMI) is an emerging cyber–physical threat to sensorless motor drives that rely on accurate current feedback. This paper presents an experimental study of radiative EMI attacks on a three-phase GaN inverter operating under sensorless field-oriented control. Specifically, non-contact EMI intrusion is investigated to examine how it may disrupt current sensing and electrical angle estimation, resulting in torque degradation and eventual loss of synchronism. Beyond instability, an adaptive EMI attack is presented in which disturbance amplitude is adjusted using only an external rotor speed measurement and a simple mechanical torque estimator to steer the drive toward a malicious torque operating point without access to internal controller variables, demonstrating that EMI can function as a controllable analog attack channel rather than a random disturbance. Additionally, a physics-based detection technique is proposed that provides early, low-latency attack detection under the tested conditions by tracking torque consistency across the mechanical and electrical domains. Experimental results demonstrate the effectiveness of both the adaptive attack and the proposed detector.