The difference between brushless DC motors and brushed DC motors
1.Structural differences between brushless DC motors and brushed DC motors
Brushed DC motors are the simplest and earliest motors. Brushed DC motors consist of armature windings, stator commutators, permanent magnets or electromagnets, and brushes. The rotor is enclosed inside the stator, and the stator of a DC brush motor also contains permanent magnets or electromagnets.
The brushes are made of carbon, and when the shaft rotates, they come into contact with the commutator. The action of the commutator is to reverse the direction of current flow when the armature coils are aligned with the north and south poles of the stator. A commutator changes current polarity by supplying itself with power and rotating the current. This reverse current phenomenon is also called mechanical reversal.
The working principle of a brushless DC motor is the same as that of a brushed DC motor, but the structure is different. In a brushless DC motor, the stator contains coil windings made of slotted laminated steel, and the rotor is fitted with permanent magnets. This means that the stator, which is the rotating part of the brushless DC motor, is fixed in the brushless DC motor, and the permanent magnets are fixed in the brushless DC motor, which is the rotor. Brushless DC motors also do not have mechanical commutators or carbon brushes.
The switching of a brushless DC motor is much more complex than that of a brushed DC motor, so it uses electronic components electronically. These electronic assemblies typically place sensors along the magnetic poles. These sensors provide feedback to the control center, which helps estimate rotor position. There are three sensor-based commutation algorithms: sinusoidal commutation, trapezoidal commutation and vector control or field control.
2.Comparison of Characteristics of Brushless DC Motors and Brushed DC Motors
Brushed DC motors are cheap, reliable, and with a high torque-to-inertia ratio, brushed DC motors are suitable for operation in harsh conditions. But the downside of brushed DC motors is that they need to be cleaned or replaced regularly as the continuous contact brushes wear out over time. Therefore, brushed DC motors are not a wise choice if the application requires a long service life and requires maintenance after a period of time.
The driving of a brushless DC motor is complicated by the need for a controller compared to a brushed DC motor which does not require any controller. A brushed DC motor can also be connected to an Arduino controller, but it is more complicated to connect a brushless DC motor to an Arduino controller, and a brushless DC motor uses an electronic speed controller as an interface to a microcontroller. Due to the complexity of the design, the cost of brushless DC motors increases, making them more expensive than brushed DC motors.
Additionally, brushed DC motors have a lower maximum speed, which limits their applicability. The cooling of brushed DC motors is also poor. In contrast, BLDC motors do not heat up because there are no sliding parts in BLDC motors, and the heat generated inside the rotor is dissipated by the larger motor housing of BLDC motors, and they have no friction and can provide more good performance. Compared to brushed DC motors, brushless motors have better performance and higher efficiency. Additionally, brushless DC motors are low maintenance and have no brushes to wear.
If we don't consider efficiency and maintenance, brushed DC motors are preferred. In the case of brushless motors, brushless DC motors have a higher initial cost, but are easier to maintain than brushed DC motors.
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