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Brushless DC motor works and application characteristics

2014-02-14 09:17      Click:

Brushless DC motors and DC motors generally have the same working principle and application characteristics , and its composition is not the same . In addition to the motor itself , but the former is more than a commutation circuit , the motor itself and commutation circuits closer together. Many small power motors and motor commutation circuit itself is synthetic one, watching brushless DC motor and DC motor from exactly the same appearance .

Brushless DC motor motor itself is part of electromechanical energy conversion , which in addition to the motor armature , permanent magnet excitation of two components, but also with sensors. Motor itself is a brushless DC motor core , it is not only related to performance indicators, noise and vibration , reliability and service life , but also the manufacturing cost and product cost. As a result of the magnetic field of permanent magnet , brushless DC motor to get rid of the traditional design and structure of the general DC , to meet the requirements of various applications market , and toward the province of copper materials, manufacturing simple direction. Permanent magnetic field is closely related to the development and application of magnetic materials , the application of the third generation of permanent magnet materials , prompting brushless DC motors to high efficiency, compact , energy-saving direction.

To achieve electronic commutation position signal must have a control circuit . Early position signal obtained with electromechanical position sensors , has gradually gained position signal electronic position sensor or other methods , the easiest way is to use the potential of the signal as a position signal armature windings .

To achieve motor speed control must have speed signal . The method used to obtain the position signal obtained similar speed signal , the speed sensor is the easiest type tachometer generator and frequency measurement electronic circuits combined.

DC brushless motor driven by a commutation circuit and the control of two parts, it is not easy to separate the two parts , in particular with low-power integrated circuits tend to become two single ASIC .

In large power motor , the drive circuit and the control circuit may each be integrated . Electric power driving circuit outputs the drive motor armature winding and controlled by the control circuit . Currently , the driver circuit state transition from linear amplification of a pulse width modulated switching state , from the corresponding circuit of the transistor circuit is converted into a discrete modular integrated circuit. The modular composition in the form of integrated circuits have power bipolar transistors , insulated gate field effect power FET and bipolar transistors . Although insulated gate field effect transistor bipolar expensive , but reliable safety and performance standpoint, it is more appropriate choice .

The control circuit used to control motor speed, steering, electric current ( or torque ) and the protection of the motor overcurrent, overvoltage, overheating . The above parameters into analog signals easily , using this relatively simple to control , but the development , the parameters of the motor should be converted into digital, the digital control circuit to control the motor. The current control circuit has a dedicated integrated circuits, microprocessors and digital signal processors , three composition . In less demanding situations for motor control , application specific integrated circuits consisting of a control circuit is a simple and practical way . Digital signal processor control circuit is composed of the future direction of development, relevant digital signal processor AC synchronous servo motors are described below .

Currently, small -power brushless DC motor areas is rapid development of the new motor. Due to various applications require their own unique brushless DC motor , so many types of brushless DC motor. There are computers in general as well as external memory VCD, DVD, CD spindle drive motor with flat coreless structure , small fan with external rotor motor structure , appliances and multi -pole magnetic structure built structure, multi-pole electric bikes , external rotor structure, etc. . Brushless DC motor above the motor itself and circuits are integrated , easy to use , its production is also very large. In order to meet the high-volume , low-cost market needs, brushless DC motor production must be economies of scale. Therefore , brushless DC motor is a high input, high output of the industry. At the same time , we should take into account the market is constantly evolving, such as home air conditioning motor is turned by the 3A 3D, requires a lot of small and medium -power DC brushless DC motor, the research and development of small and medium -power DC brushless motor is also a priority.

    Brushless DC motor (BLDCM) is based on a brushed DC motor to develop , but it is an absolute drive current exchange ; brushless DC motor speed can be divided into brushless motors and brushless torque motors . Generally , the brushless motor driving current , there are two , one is trapezoidal wave ( generally " square wave " ) , the other is a sine wave. Sometimes called the former a brushless DC motor , the latter called AC servo motors , AC servo exactly say what is a motor.

    Brushless DC motor in order to reduce the moment of inertia , usually a " slim " structure. Brushless DC motor in terms of weight and volume than brush DC motors smaller, the corresponding moment of inertia can be reduced by about 40% -50 %. Since the permanent magnet materials processing problems , resulting in a brushless DC motor in the capacity of general 100kW or less.

    Mechanical characteristics of this motor and regulation characteristics of linearity, wide speed range, long life , easy maintenance and low noise, not a series of problems caused by the brush , so this has a great motor control system potential applications.

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