Motors and motor controllers play an important role in many fields, especially medical and robotics applications. In addition, the recently popular new energy vehicle field has an increasingly obvious demand for small, high-efficiency, high- and low-torque, and high-power and low-power motors.
These end devices can choose from brushed DC motors, brushless DC (BLDC) motors, or a combination of the two. Most motors operate according to Faraday's law of induction. Still, there are key differences between brushed and brushless motors and the range of their applications.
Let's introduce the difference between brushed motors and brushless motors. First, we will introduce brushed DC motors.
Brushed DC Motor
Since about the late 1900s, brushed DC motors have been one of the simplest types of drive motors, and today a typical brushed DC motor consists of an armature (also called a rotor), commutator, brushes, shaft, and field magnets . Of course, the brushed motor needs to provide the DC power or battery power required for operation at the same time, and obtain the rotational torque through the rotating magnetic field, thereby outputting kinetic energy.
1. Simple structure, general DC brush motor includes armature or rotor, commutator, brush, shaft and field magnet. Of course, a battery or power supply is required. The properties of a motor depend on the material it is made of, the number of coils wound around it, and the density of the coils. The armature or rotor is an electromagnet and the field magnet is a permanent magnet. The commutator is a split ring device around the shaft that makes physical contact with the brushes, which are connected to the positive and negative poles of the power supply.
2. A commutator around the shaft, the commutator is in contact with the brushes, which are connected to opposite poles of the power supply to deliver positive and negative charges to the commutator. The brushes drive the rotor to rotate with the magnetic field generated by inputting the opposite polarity power through the commutator. The rotation direction is clockwise and/or counter-clockwise, and the forward and reverse rotation of the motor can be realized by changing the polarity of the brushes.
Brushless Motor (BLDC)
Brushless Motor
The working principle of the brushless DC motor is the same as the magnetic attraction and repulsion principle of the brushed motor, but their structure is slightly different. The brushless motor, as the name implies, has no brushes, adopts electronic commutation, the coil does not move, and the rotor rotates. The work of commutation is handed over to the control circuit in the controller. High efficiency is the main selling point of BLDC motors. Because the rotor is a NdFeB magnet (NdFeB magnet), that is, no connection, no commutator and brush are required, so that the rotor works very efficiently.
Brushless motors can have either the rotor on the inside or the rotor on the outside of the windings (sometimes called an "outer rotor" motor). The number of windings used in a brushless motor is called the number of phases. Although brushless motors can be constructed with different numbers of phases, three-phase brushless motors are the most common. The three windings of a brushless motor are connected in a "star" or "delta" configuration. In either case, there are three wires connected to the motor (commonly referred to as U, V, W), and the drive technique and waveform are the same. At the same time, in order to detect the position of the rotor at a specific time in the brushless motor, some brushless motors will be driven together with Hall sensors, and there are more accurate technologies that use magnetic encoders. As the magnetic rotor turns, Hall sensors pick up the rotor's magnetic field. After the driver IC receives the signal, it calculates and passes the current through the stator windings in sequence, thereby driving the rotor to rotate.
The above is a brief introduction to the difference between brushed motors and brushless motors.
