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Difference between Brushed and Brushless Motors

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Brushless DC motors are the one which use an electronic commutation and are powered through a DC source using switching supply and an inverter, which basically generates an AC electrical signal for driving the motor in order to drive the motor. Performance is the main concern for such motors and since the rotor is the only carrier of the magnets, it does not require any power means no commutator and no brushes.

On the other hand, a Brushed motor is the one that possesses an internal commutation and is fabricated in a way to run by DC supply. The machine brushes essentially charge the commutator in a reverse polarity with respect to a permanent magnet, which causes the armature to rotate. The motor’s rotation can be reversed easily by changing the brushes polarity (which can be done by reversing the battery leads).

The key differences between Brushless and Brushed DC Motor are explained in this article on the basis of real-world factors such as efficiency, speed & torque adaptability, Size, Life, Speed Range, Noise, Maintenance, Control, Cost, Commutation Process, and Rotor Inertia. The following table keys out the main differences between Brushless and Brushed DC Motor.

Difference between Brushed and Brushless Motors

CharacteristicsBrushless DC MotorBrushed DC Motor
LifeLonger since no brushes Shorter because of brushes wear out
Speed/Torque CharacteristicsFlat — which actually Enables it’s operation at all speeds within rated loadModerately flat — Actually brush friction increases at higher speed which in turn reduces useful torque.
EfficiencyHigh — because there is no voltage drop across brushes.Moderate
Output power/frame sizeCondensed size because of due to better thermal characteristics. Since it has the windings on the stator, which is coupled with the case, the overall heat dissipation is much better.The heat dissipation in the air gap, produced by the armature, increases the temperature significantly in the air gap, thus limiting the specification on the output power/frame size.
Rotor InertiaLow since it has permanent magnets on the rotor which in fact improves the dynamic response.Possesses higher rotor inertia thus limiting the machine dynamic characteristics.
Speed RangeHigher—Since there are no mechanical limitations because of brushes and commutator.Lower — because of Mechanical limitations imposed by by the brushes.
Electric Noise GenerationLowArcs in the brushes generate noise which causes Electromagnetic Interference (EMI) in the nearby equipment.
Cost of BuildingBecause of permanent magnets, cost is high.Low.
ControlComplex and expensive.Simple and inexpensive.
Control RequirementsA controller is required in order to keep the motor in operation. The same controller can be utilized for variable speed control (VSC).For fixed speed, no controller is required. If variable speed is desired then a controller is needed.
CommutationIt employs Electronic commutation process which is based on the Hall position sensor.Brushed commutation.
MaintenanceSince no brushes so less maintenance is required.Maintenance is required quite frequently.

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About Ahmad Faizan

Mr. Ahmed Faizan Sheikh, M.Sc. (USA), Research Fellow (USA), a member of IEEE & CIGRE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from Kansas State University, USA.