Fundamentally, both brushed and brushless motors convert electrical energy into rotational kinetic energy by leveraging the principles of electromagnetism. However, the distinct architectures of these motors result in vastly different performance characteristics. In this discussion, we explore the advantages of brushless motors over their brushed counterparts.
The brushed motor, a relatively simple design, was the initial electric motor widely adopted for various applications. Consisting of a stator and a rotor, the stator comprises a stationary ring of permanent magnets, while the rotor, located inside the stator, consists of electromagnetic windings connected to a commutator. The commutator, in constant contact with brushes fixed on opposing sides, enables the rotation of the rotor by cycling direct current through the different phases of the windings, a process known as commutation.
Brushless motors eliminate brushes and employ electronics for motor commutation. In these motors, an electronic circuit, such as an optical encoder or Hall-Effect sensors, detects the rotor's position relative to the stator. It then supplies current through the three-phase pairs of the stator windings, maintaining a 120° phase offset between each, ensuring smooth rotation with low torque ripple. This design, made possible by the development of solid-state electronics in the 1960s, offers several advantages over traditional brushed motors.
Quieter Operation: Friction and electrical arcing in brushed motors generate significant noise. Brushless motors, relying on electronic circuitry for commutation, operate much more quietly.
Reduced Heat Production: The friction between brushes and commutator plates in brushed motors results in substantial heat production. Brushless motors, with minimal friction occurring only in rotor bearings, experience significantly less heat generation.
Higher Efficiency: Brushless motors exhibit higher efficiency as the reduction in noise and heat production minimizes power losses. This increased efficiency translates to more effective energy utilization.
Extended Motor Life: Brush wear in brushed motors necessitates eventual replacement, leading to maintenance requirements. Brushless motors, devoid of this issue, offer extended operational life and find utility in applications where brush replacement is impractical.
Improved Power-to-Weight Ratio: With fewer mechanical components, brushless motors have lower mass compared to brushed motors. Consequently, they boast superior power-to-weight and torque-to-weight ratios, contributing to enhanced overall performance.
In summary, the technological advancements represented by brushless motors, with their reliance on electronic commutation, provide a significant array of benefits, including quieter operation, reduced heat production, higher efficiency, extended operational life, and improved power-to-weight ratios.