When the application allows, design engineers may opt for brushless motors in place of brushed motors because they operate with relatively little maintenance, generate low electrical noise, can operate at higher voltages, may be more efficient and can be made more compact.

The three most common types are brushless DC, brushless servo and brushless torque.The three most common types are brushless DC, brushless servo and brushless torque.So says an Allied Motion blog describing the function of three types of brushless motors: brushless DC, brushless servo and brushless torque.

(Learn more about brushless motors and find products and suppliers at Engineering360.)

Brushes in brushed motors are used in the commutation process to switch current from coil to coil, to develop torque and spin the rotor and attached load. Brushless motors use electronics to accomplish the commutation task. The electronic switching of currents to the coils of the motor is efficient, and there is no wear nor replacement of brushes or commutators. Brushless DC motors are used in pumps, fans and blowers, compressors and other similar applications. They also are found in battery-powered devices, since their relatively high efficiency may prolong battery life.

When applications require precise positioning or high speeds, brushless servo motors may be appropriate. They typically are designed for quick, accurate response in highly dynamic applications, the blog says. Also available are frameless brushless servo motors, used when designers may prefer to embed the motor in the mechanics. This practice helps to ensure tight coupling to the driven component and can result in a compact design.

Applications typically using brushless servo motors include robots, pick-and-place equipment, semiconductor fabrication, test and packaging equipment and machine-tool axes.

Brushless torque motors are designed to produce a lot of torque at comparatively low speeds, the blog says. Compared to using gear motors in low-speed precise-positioning applications, brushless torque motors are mechanically simpler, more efficient and avoid the backlash inherent in geared systems.

Compared to other motor types, torque motors have more poles and are larger in diameter. As such, the blog says they can produce more torque per volume and weight. And, they can be combined with large-diameter high-count encoders to reach arc-second levels of rotary positioning precision.

Torque motors find use in robotic joints, simulators, multi-axis tracking and positioning gimbals, GPS-based automated-vehicle steering systems, and in the motion systems of movie cameras.

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