Improved efficiency of a fan drive system without using an encoder or current sensors

Abstract

This study proposes a closed‐loop fan drive system without using an encoder or current sensors. The cost and size of the fan drive system, therefore, are significantly reduced. By using low‐resolution three‐phase Hall‐effect position sensors, three‐phase sinusoidal pulse‐width modulation voltages are generated to control a permanent magnet synchronous motor (PMSM) that a fan is connected to. Two methods, including the back‐EMF estimation method and the impedance‐phase estimation method, are proposed to determine the input voltage amplitude and phase of the PMSM. A digital signal processor, TMS 320F28335, is used to execute the control algorithms. The proposed impedance‐phase estimation method is 25% more efficient than the back‐EMF estimation method at low‐speed operating range – below 1000 r/min. A detailed sensitivity analysis of the motor parameter variations is discussed. The implemented drive circuit, which is very compact, can be attached at the back of the PMSM and fan. Several experimental results are provided.