Brushless Direct Current (BLDC) machine is a kind of permanent magnet AC machine, and is named this way because of many similarities with DC machine. The structure and design of this machine is very similar to the permanent magnet synchronous machine (PMSM). One of the differences between these two kinds of machines is their stator-winding induced voltage versus electrical angle. Therefore this machine is also called trapezoidal permanent magnet ac machine. Due to its high torque per volume ratio, maintenance free, low inertia and ease of heat exchange, new applications for this machine type are coming along. So, improving the drive circuit of this machine, in parallel with expansion of its application, is of engineers’ interest. One of the performance improvement methods for this drive is reducing the switching losses and its inverter electro-magnetic interference, without major extra costs. To achieve this goal, employing soft-switching techniques for inverter is an appropriate option. In soft- switching techniques, by adding auxiliary circuits to inverter main circuit, voltage and current change incidence can be significantly reduced, and switching losses are almost eliminated. Improving power quality characteristic of system input side, and lowering costs are other fields of interest. In this thesis first, three phase brushless DC machine and its operational principles are introduced. Then, other types of this machine with their basic drive methods are described. Then by using a The aim of this thesis is presenting a soft-switching topology with fewer elements compared to other presented soft-switching inverters. So in chapter five, such a topology with its drive method is proposed. Then the proposed topology is analyzed by explaining its operating principle and its drive method. Thus, by explanation of the design method, a prototype of the proposed topology- in accordance with an available motor- is designed. By explaining the simulation method and elements modeling used in simulator program, the proposed topology is simulated, and simulation results are presented. A digital signal processor is used for the implementation of this inverter. This processor computes instantaneous speed, and realize control loop. Also the processor generate control signal, by receive and analyzing of hall-effect sensors data. For final implementation of this topology, signal shaper circuits and gate drive for power switches are designed and implemented. Finally, experimental results of implemented topology are shown, and which are quite closed to the expected ones. The thesis is ended by concluding the results and making some suggestions for future works. Key Words: Brushless DC motor, soft-switching, inverter, resonant pole inverter, zero voltage switching
