Electrical motors are an integral part of industrial plants with no less than 5 billion motors built world wide every year. Development of advanced motor drives has yielded increase in efficiency and reliability. Residential and commercial applications such as refrigerators and air conditioning systems use conventional motor drive technologies. The machines found in these appliances are single phase induction motors or brushed DC machines which are characterized by low efficiency and high maintenance, respectively. On the contrary a brush-less DC (BLDC) motor drive is characterized by higher efficiency, lower maintenance and higher cost. In a market driven by profit margins, the appliance industry is reluctant to replace the conventional motor drives with advanced motor drives (BLDC) due to their higher cost. Replacing these inefficient motors, with more efficient brush-less DC motors (BLDC) will result in substantial energy savings. Therefore it is necessary to have a low cost, but effective BLDC motor controller. This thesis lays the groundwork for the development of a novel low-cost IC for control of BLDC motors.
A simple novel digital pulse width modulation (PWM) control has been implemented for a trapezoidal BLDC motor drive system. This digital controller treats the motor like a digital system. Based on the speed error and the actual value of the motor current, the controller selects a high duty, low duty or a skip state. Speed regulation is achieved by alternating between these states. Due to the simplistic nature of this control, it has the potential to be implemented in a low cost IC. Describing function method and Fourier analysis were used to prove the stability of the motor-drive system.
Most three-phase motors, including BLDC motors need at least six PWM channels for inverter power devices such as IGBTs and MOSFETs. Field Programmable Gate Array (FPGA) is used to generate the control signals. Designing the controller using an FPGA presents several advantages such as small drive size and less development time. Simulation results are presented, for various commanded speed and load torque. Experimental verification is carried out using to validate the claims presented.
|School:||Illinois Institute of Technology|
|School Location:||United States -- Illinois|
|Source:||DAI-B 70/08, Dissertation Abstracts International|
|Keywords:||Brushless DC motor, Digital control, Energy efficient, Low-cost drives, Motor drives, PWM control, Pulse width modulation|
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