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
Miniaturization, increased speed, and higher accuracy for industrial positioning devices have recently been the main requests for industrial upgrades. Using linear motors is an effective way to meet these requests. This paper discusses a linear DC motor (LDM) for high-speed positioning. One high-speed positioning approach decreases the mechanical time constant for LDMs. The LDM with the smallest mechanical time constant (4.1 ms) was designed and manufactured within the overall dimensions: 72×75×62 mm3. The positioning device with the manufactured LDM positions a 0.2 kg load with 10 mm stroke in 27 ms
