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Brushless DC motor

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Brushless DC motor is realized by electronic commutation of the semiconductor switching device, which uses electronic switching devices to replace the traditional contact type commutator and brush. The system has the advantages of high reliability, no commutation spark and low mechanical noise, and is widely used in high grade sound recording, video recorder, electronic instrument and automatic office equipment.
Brushless DC motor is composed of permanent magnet rotor, multi pole winding stator, position sensor and so on. Position sensing according to the change of rotor position, along a certain order of the stator winding current of converter (i.e. detection position of the magnetic poles of the rotor relative to the stator winding, and position sensor signal are generated in the determination of the position, after signal conversion processing circuit to control the power switch circuit, according to certain logical relation were winding current switching). The operating voltage of the stator winding is provided by an electronic switch circuit which is output controlled by the position sensor.
Position sensor has three types: magnetic sensor, photoelectric type and electromagnetic type. The magnetic position sensor brushless DC motor, the magnetic sensor parts (for example Hall element, magnetic diode, magnetic sensitive Gu polar tube, magnetic sensing resistor or application specific integrated circuit) mounted on the stator component and used for detection of permanent magnet, when the rotor rotation magnetic field changes.
A photoelectric sensor is arranged on the stator assembly, and a light shielding plate is arranged on the rotor, and the light source is a light emitting diode or a small bulb. When the rotor rotates, due to the action of the light shielding plate, the photosensitive element on the stator will be born with a pulse signal between a certain frequency and a certain frequency.
The magnetic position sensor of Brushless DC motor, electromagnetic sensor components (e.g. coupling transformer, a proximity switch and an LC resonant circuit is arranged in the stator assembly), when the permanent magnet rotor position changes, electromagnetic effect will make electromagnetic sensors to generate a high frequency modulation signal (the amplitude varies with the rotor position change).
Superiority
DC motor has a fast response, large starting torque,
Physical diagram of electric machine
Physical diagram of electric machine
From zero speed to the rated speed with rated torque performance, but the advantages of DC motor is its disadvantages, because DC motor to produce the rated load under constant torque performance, armature magnetic field and the magnetic field of the rotor must be constant to maintain 90 degrees, which would be by brush and commutator. Carbon brush and commutator motor rotates in will generate sparks, toner so in addition to cause damage to components, use the occasion is restricted. AC motor without carbon brush and commutator, free maintenance, rugged, wide application, but properties if you want to reached a considerable in the performance of DC motor shall be with complex control technology to achieve. Nowadays, the rapid development of semiconductor power components to speed up the switching frequency of many, enhance the performance of the drive motor. Micro processor speed more and more fast can be realized AC motor control placed on a rotating axis orthogonal coordinate system, proper control of AC motor in the two axis current component, reached similar to DC motor control and performance comparable to that of DC motor.
Also has a lot of micro processor control motors are required to function in the chip, and the volume is more and more small; like analog / digital converter (Analog-to-digital converter, which ADC), pulse width modulation (pulse wide modulator PWM). Etc.. The brushless DC motor is a kind of application which is controlled by the electronic way to control the commutation of the AC motor, which is similar to the DC motor and has no DC motor mechanism.