Torque Ripple In Brushless Dc Motor

The brushless DC motor (BLDCM) is a DC motor using electronic commutation instead of the mechanical commutation, so it has excellent characteristics of DC motors, such as good start and timing performance, and on the other hand it overcomes the friction disadvantages of ordinary DC motor radically with its simple brushless structure. It has been extensively used in many industrial domains, such as aviations, robots, digital machine tools, and in medical or home appliances. But the BLDCM has the disadvantages of torque pulsation, which is in the way of achieving accurate position and speed of higher performance. The objective of this dissertation is to study the control technology to minimize the torque pulsation of BLDCM.From the basic operation principles and electromagnetic relations of the brushless DC motor, this paper analyses the reasons of producing torque pulsation and establishes the mathematical model. The dissertation especially details the torque pulsation produced by commutation and commutation dead band (CBD), and through theoretical and mathematical analysis, some rational approaches are proposed to eliminate this kind of torque pulsation. The simulation and experimental results are provided to demonstrate the validity of the proposed method.Taking a brushless DC motor with power of 2.2kW as object, this dissertation designs high performance control system with TMS320LF2407 as its microprocessor. The control system also adopts IM13400 intelligent power module (IPM) produced by Cyntec to enhance the integral reliability and security. The small and high efficiency switch power is used in this system to supply power for the control system, drive circuit, and other extended function circuits. In software, the method of reducing commutation torque pulsation is brought into effect.