Understanding Brushless DC Motor components will help show why Brushless DC motors are so much more reliable, require no maintenance and offer virtually unlimited lifetimes compared to conventional Brush DC Motors.
But first, for proper perspective here’s a quick overview of “Brush” motor components.
Looking from the outside-in, a Brush DC Motor has a stator made up of a metal enclosure surrounding attached magnets that create a permanent magnet field. The interior rotor, which is attached to the rotating output shaft, has a metal structure supporting copper wire coils which, when energized, become electromagnets. Through the attraction of opposite magnetic poles and the repulsion of like poles a torque is created that turns the rotor.
But, in order to selectively energize the rotor coils in order to create rotation it requires a commutator, which basically is a segmented copper assembly that energizes the coils when it makes contact with a conductive carbon brush. Hence, the name Brush DC Motor.
However, the carbon brushes wear over time, and the commutator does too, although more slowly. Therefore, the Brush DC Motor has a finite life. In addition, the brushes making contact with the rotating commutator are also a source of noise: not only audible noise, but also electrical “noise” in the form of electromagnetic interference (EMI) as a result of the minute arcing that occurs when contact is made and interrupted. In many applications, however, the Brush DC Motor can be a reliable solution.
But when maximum lifetimes with no maintenance, no audible noise and no EMI are desired, the Brushless DC Motor is the right solution.
Brushless DC Motor Components Eliminate Wear Parts
Brushless DC Motor components are made up of three main elements:
- A fixed part, the stator, which has three groups of coils, called the three phases of the motor. These coils operate as electromagnets and generate various orientations of magnetic field regularly distributed around the central shaft of the motor.
- A rotating part, the rotor, which has permanent magnets. Like the needle of a compass, these magnets permanently drive the rotor to try to align itself with the magnetic field of the stator. For optimum service life of the motor, the rotor is mounted on ball bearings.
- Three “Hall effect” magnetic sensors. These sensors provide information on the position of the rotor magnets at all times. These sensors use dependable solid state electronics to commutate the Brushless DC Motor, instead of the wear-prone brush and commutator electromechanical assembly used in Brush DC Motors.
However, the Brushless DC Motor requires an electronic control to activate the phases of the motor, which the Brush DC Motor does not. Fortunately, advances in electronics have made the control smaller, less expensive and capable of offering many value added features. Brushless DC Motor Controls will be covered in another upcoming post.
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