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. Mechanical speed, adjustable speed drive need any setting 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 mainly three kinds of commonly used motor: dc brush motor, brushless dc motor and induction motor. In the packaging machinery, food machinery, printing machinery, material conveying machinery, textile machinery and transportation vehicles in a large number of applications. Adjustable speed system application domain with the more is the dc motor at the beginning, as the 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 to infiltrate the original application field of the vast majority of dc speed regulating system. In recent years, because of the brushless dc motor 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. , 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, with the progress of power electronic technology, the power is not greater than the 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 is replaced by the brushless dc motor, 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 drives and other devices, should be added to so less application current brushless motors. , precision servo motor in the field of industrial automation control 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/current control, speed control and position control. Brushless dc motor due to the good control performance, in the high speed, high precision positioning system gradually replace the dc motor and stepping motor, become one of the modern choice of motor servo system. At present, scanner, camera, CD drive, drive, medical diagnostic CT, computer hard disk drives, and numerical control lathe driving medium are widespread adoption of brushless dc motor servo system for precision control. Household appliances, and other applications such as automatic washing machine, CD player, etc. Military applications such as submarines, ships; There are large synchronous motor start-up, etc.
