The disadvantages of the Brushless DC Motor over the AC motors are:
higher maintenance (due to brushes)
more expensive
In addition to the above the Brushless DC Motors have the same advantages over AC motors but they also have more advantages over Brushed DC Motors
lower maintenance (no brushes)
even higher starting torque ( Due to rare earth magnets)
even higher efficiency (over 90%) on sub fractional motors
even more compact design
better heat dissipation
lower noise
This paper considers the development of a smooth "starter" for a DC motor based on a switch controlled DC-to-DC power converter of the "buck" type. The dynamic feedback controller is based on a suitable combination of passivity based control, flatness and a Σ - Δ modulator implementation of the average designed controller. The scheme proposes an indirect regulation of the motor shaft speed by means of input current regulation on the "buck" converter circuit. As a consequence, the proposed feedback controller does not require the use of an electromechanical velocity sensor for measuring the angular velocity. The effectiveness of the proposed controller was verified by computer simulations using the P-Spice circuit simulation program.
