Brushless dc motor of the machine itself is electromechanical energy conversion part, it besides motor armature, permanent magnet excitation two points, also with sensors. Motor itself is the core of the brushless dc motor, it is not only related to the performance index, noise, vibration, reliability and service life, etc. , involving the manufacturing costs and product cost. Because use permanent magnet magnetic field, make the brushless dc motor from the traditional design and structure of the dc motor commonly, meet the requirements of various applications market, and development in the direction of the province copper material saving, simple and convenient manufacturing. Permanent magnet magnetic field is closely related to the application of permanent magnetic material, the development of the third generation of the application of permanent magnetic material, make brushless dc motor to efficiency, miniaturization, energy-saving direction. in order to achieve the electronic commutation must have a position signal to control the circuit. Early with the mechanical and electrical position sensor position signal, has been gradually use electronic position sensor or other ways to get position signal, the easiest way is to use the armature winding voltage signals as position. so as to realize the control of motor speed must have a speed signal. With similar position signal obtained speed signal, the simplest speed sensor is type tachogenerator frequency measurement combined with electronic circuits. the brushless dc motor reversing circuit consists of two parts, drive and control, it is not easy to separate the two parts, especially small power circuit integration between the two usually become single application-specific integrated circuit. in the power of the larger motor, drive circuit and control circuit can become one. Drive circuit output power, drive motor armature winding, and controlled by the control circuit. The driver circuit has from the linear amplification state into PWM switch state, the corresponding circuit composition also from transistor discrete circuit into modular integrated circuit. Modular integrated circuit with power bipolar transistors, power field effect tube and isolation gate field effect in the form of a bipolar transistor, etc. Although, isolation bipolar transistor gate field effect the price is more expensive, but from the perspective of the safe and reliable performance with it is more appropriate. control circuit used for control motor speed, steering, current (Or torque)As well as the protection of motor over-current, over-voltage, overheating, etc. The above parameters easily converted to analog signals, use this to control is relatively simple, but from the point of development, the parameters of the motor should be converted to digital quantity, through the digital control circuit to control the motor. At present, the control circuit has a special integrated circuit, microprocessor and digital signal processor of three kinds of ways. On the occasion of motor control request is not high, application-specific integrated circuit of control circuit is simple and practical way.
