Earticle

This thesis develops efficiency optimization control strategies for three phase induction motors with Hall sensor. This thesis compares the different control strategies include open-loop voltage-mode control of hard-commutation scheme, open-loop voltage-mode control of soft-commutation scheme, and closed-loop current-mode control scheme, and analyzes the current response and overall efficiency. This thesis also develops a low-cost and high efficiency sensorless control for three phase induction motors drives. The proposed scheme detects the back-EMF zero-crossing-point (ZCP) to realize current commutation without Hall sensor. An adjustable blanking time control method is used to ensure correct detection of the ZCP. When using sensorless commutation control, the fan motor can start-up smoothly and operate under wide speed range, moreover, the overall efficiency is almost the same to the results of control scheme with Hall sensor.