A brushless DC motor principle and explain the application

1 Introduction
In this paper, the development of motor types in the rapid development and application of a wide range of Brushless DC motor (www.hkhaibo.com) (hereinafter referred to as BLDC). BLDC is widely used in daily life appliances, automobile industry, aviation, consumer electronics, medical electronics, industrial automation and other devices and instruments. Just as its name implies, BLDC without the use of mechanical structure of the commutating brush directly using electronic commutator, in use BLDC compared with brush motor has many advantages, such as:
Can get better torque speed characteristics;
High speed dynamic response;
High efficiency;
Long life;
Low noise;
High speed.
In addition, the BLDC better torque and shape than the size makes it more suitable for the motor's own weight and the size of the more sensitive occasions. In this application note will discuss a series of structure, basic principle, characteristic and application of BLDC. May be used to explore the process of the term can be found in Appendix B "glossary" in the corresponding explanation.
The structure and basic principle of 2 BLDC
BLDC is a kind of synchronous motor. This means that the magnetic field generated by the stator rotor and its magnetic field is the same frequency, so BLDC does not produce ordinary induction motor frequency difference phenomenon. Are there in BLDC single phase, the 2 phase
The difference between the 3 phase motor, how many different types of decision of the stator coil winding. Here we will concentrate on the 3 phase is the most widely used BLDC.
2.1 stator
The BLDC is composed of many silicon steel sheet after lamination and axial stamping, punching each have a certain composition of the coil winding, can see the figure below. In the traditional sense, BLDC induction motor stator and stator are similar, but there are some differences in the distribution of the stator windings. Most of the 3 BLDC stator winding is star row steel sheet, each winding by many internal combined in a certain way, even in the stator winding distribution surrounded by an even number of magnetic poles.
The internal structure diagram of 2.1.1. BLDC
BLDC stator windings can be divided into trapezoidal and sinusoidal two windings, the fundamental difference between them is due to the winding of different connected in such a way that they produce anti electric motive force (anti electric motive force of the relevant information, please to EMF section), respectively, showed the trapezoidal and sinusoidal waveform, so the named. The waveform of trapezoidal and sinusoidal winding back EMF generated by the as below.

There is also a need of counter electromotive force of the winding is different the phase current is also presented in the trapezoidal and sinusoidal waveform, imagined sine winding due to smooth waveform so running up relative trapezoidal windings is more stable. However, because there are more sinusoidal winding winding in the copper wire used on the winding ladder relative to.
Usually because the applied voltage is different, we can according to need to choose different brushless motor voltage range. In the automotive, robotics, small mechanical arm can motor 48V and below voltage application. In the special equipment, automatic control and industrial production field can motor 100V and above voltage range.
2.2 rotor
The stator is 2 to 8 of the permanent magnet in accordance with N and S poles composed of alternately arranged around the rotor (the inner rotor type), if the outer rotor type BLDC is attached to the inner wall of the rotor. As shown in figure 2.2.1;