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A simplified current controlled modulation technique for brushless DC motors is presented. It is based on the generation of quasi square-wave currents, using only one current controller for the three phases. The advantages of this strategy are: (a) very simple control scheme; (b) the phase currents are kept balanced; (c) the difficult sensing of DC link current in flat plates is avoided; and (d) the current is controlled through only one DC component. These characteristics allow to use the triangular carrier as a current control strategy for the power transistors, which is simpler and better than other options. Computer simulations using power electronic simulator (PSIM), have been developed to show the good characteristics of this solution, and its simplicity. Some experiments with a 15 kW motor-inverter system, show the excellent behavior under steady-state, and transient situations, such as step response and reversal of power.
Date of Publication: March 2002