Final answer:
A brushless DC machine utilizes electronic commutation instead of mechanical brushes, ensuring high efficiency and reliability through sophisticated control of its power connection.
Step-by-step explanation:
A brushless DC machine is different from a traditional brushed DC motor, which uses brushes for commutation. Instead, a brushless DC machine, also known as a BLDC, utilizes a power connection with electronic means to perform the commutation, effectively replacing the mechanical brush-commutator system. A brushless DC machine does not simply apply a constant DC voltage to the phases. It uses rotor position sensors, control logic, and power electronics to adjust the phase currents and keep the motor running efficiently. The control system of a brushless DC motor is inherently more complex due to its closed-loop nature, necessitating precision electronic control to manage power application and motor position. This sophistication allows the brushless DC machine to have the benefits of a PMAC (permanent magnet alternating current) machine, which include higher efficiency, reliability, and reduced noise.