Motors exist in all aspects of our lives. The motor pla […]
Motors exist in all aspects of our lives. The motor plays the role of mutual conversion of electrical energy and mechanical energy. Both the generator and the motor are called motors. In addition to solar power plants and batteries, the remaining power generation facilities will use motors. The work of the pump, the movement of the mechanical arm, the rotation of the fan and the work of the machine tool, etc., consume the vast majority of the electrical energy from the power station.
DC motors are used very early. The energizing coil rotates under the action of the magnetic field generated by the permanent magnet or excitation coil in the motor. For a motor with a pole pair number of one, that is, a pair of magnetic poles, the pole spacing is 180°, while the rotor of the early DC motor was an energized coil, and the current was commutated every half turn. Therefore, commutators and brushes appeared. Since the two will re-contact once every half circle, it will produce sparks. The commutator process is complex, so the use of graphite materials for the brush has reduced the cost of wear. Both brushes need to be changed once in a while. Therefore, DC motors are not only limited in application occasions, but also cannot be used in flammable and explosive places. Maintenance is also troublesome and costly.
So, can the permanent magnet be used as the rotor and the coil that needs to be energized as the stator? In this way, the trouble of changing the brush can be solved, and the generation of electric sparks can also be avoided. In fact, a new type of special motor——BLDC motor, uses this structure. But in fact it is not a DC motor. The general idea is to control the order of energization of the coils, group the opposite coils into a group, and at the same time pass current to make them generate magnetic fields in the same direction. Taking the three-phase BLDC motor as an example, the number of pole pairs of the motor is three, so that each pair of "magnetic poles" are turned on in a certain order, to achieve the effect equivalent to the magnetic field turning.
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