Because of the brushless dc motor has the simple structure, reliable operation of ac motor, maintenance is convenient wait for a series of advantages, and dc motor running with high efficiency, no excitation loss and speed control performance is good, so in the various fields of national economy, such as medical equipment, instruments and meters, chemical industry, textile, becoming increasingly prevalent in, and the application of household electrical appliances, etc. The application of brushless dc motor (BLDCM) is mainly divided into the following categories: 1, the constant speed drive machinery general industrial situation does not require speed field most often adopts three-phase or single phase ac asynchronous and synchronous motor controller, with the progress of power electronic technology, the power is not more than 10 kw and under the condition of continuous operation, in order to reduce the volume and save material, improve efficiency and reduce the loss, a growing number of motor controller is replaced by the brushless dc motor controller, such applications are: automatic doors, elevators, water pump, fan, etc. And in the power of the larger situation, because of its high cost and investment, in addition to the permanent magnet motor controller should be added to the drive equipment, so the less application brushless motor controller. 2, need to set arbitrary adjustable speed drive mechanical speed and adjustment, but control of the speed control accuracy is not high. This kind of system can be divided into two kinds: one kind is open loop speed control system, the other is a closed-loop speed control system (This time the speed of feedback device with low resolution or ac, dc pulse encoder speed, etc. )。 There are three kinds of commonly used motor controller mainly: a dc motor controller, the asynchronous motor controller and brushless dc motor controller. In the packaging machinery, food machinery, printing machinery, material conveying machinery, textile machinery and transportation vehicles in a large number of applications. First used in the application of the adjustable speed system is more dc motor controller, as ac speed regulation technology especially the development of power electronic technology and the controller, ac frequency conversion technology obtained the widespread application, frequency converter and ac motor controller to infiltrate the original application field of the vast majority of dc speed regulating system. In recent years, because of the brushless dc motor controller the advantages of small volume, light weight and high efficiency and energy saving of the increasingly prominent, small and medium-sized power ac frequency conversion system is gradually replaced by brushless dc speed regulation system, especially in textile machinery, printing machinery, such as the original field frequency conversion system is widely applied. In some application fields directly by the battery power supply, now more use of brushless dc motor. 3, the precision in the field of industrial automation control servo motor plays an important role in the high precision control, different applications, control of the servo motor performance requirements are also different, in the actual application, servo motor control in different forms: torque control/current control, speed control, position control. Due to the good control performance, brushless dc motor (BLDCM) in high speed, high precision positioning system gradually replace the dc motor controller and step motor controller, become one of the modern choice of motor servo system controller. Currently, scanner, camera, CD drive, drive, medical diagnostic CT, computer hard disk drives, and numerical control lathe driving medium are widely adopted brushless dc motor servo system controller for precision control. 4, and other household electrical appliances such as automatic washing machine, CD player, etc. Military applications such as submarines, ships; There are large synchronous motor controller startup, etc.
