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Brushless motors are found in many modern cordless tools, including some string trimmers, leaf blowers, saws (circular and reciprocating), and drills/drivers. The weight and efficiency advantages of brushless over brushed motors are more important to handheld, battery-powered tools than to large, stationary tools plugged into an AC outlet.
A brushed DC electric motor is an internally commutated electric motor designed to be run from a direct current power source and utilizing an electric brush for contact. Brushed motors were the first commercially important application of electric power to driving mechanical energy, and DC distribution systems were used for more than 100 years ...
Typical brushless DC motors use one or more permanent magnets in the rotor and electromagnets on the motor housing for the stator. A motor controller converts DC to AC. This design is mechanically simpler than that of brushed motors because it eliminates the complication of transferring power from outside the motor to the spinning rotor.
BLDC motors are typically 85%+ efficient, reaching up to 96.5%, [76] while brushed DC motors are typically 75–80% efficient. The BLDC motor's characteristic trapezoidal counter-electromotive force (CEMF) waveform is derived partly from the stator windings being evenly distributed, and partly from the placement of the rotor's permanent magnets.
The rating of a brushless motor is the ratio of the motor's unloaded rotational speed (measured in RPM) to the peak (not RMS) voltage on the wires connected to the coils (the back EMF). For example, an unloaded motor of K v {\displaystyle K_{\text{v}}} = 5,700 rpm/V supplied with 11.1 V will run at a nominal speed of 63,270 rpm (= 5,700 rpm/V ...
A motor controller converts DC to AC. This design is simpler than that of brushed motors because it eliminates the complication of transferring power from outside the motor to the spinning rotor. An example of a brushless, synchronous DC motor is a stepper motor which can divide a full rotation into a large number of steps.
Brushed linear motors were used in industrial automation applications prior to the invention of Brushless linear motors. Compared with three phase brushless motors, which are typically being used today, brush motors operate on a single phase. [3] Brush linear motors have a lower cost since they do not need moving cables or three phase servo drives.
High-power, brushless axial motors are more recent, but are beginning to see usage in some electric vehicles. [8] One of the longest produced axial motors is the brushed DC Lynch motor, where the rotor is almost entirely composed of flat copper strips with small iron cores inserted, allowing power-dense operation.