DC motor has a fast response, large starting torque from zero speed to rated speed with rated torque performance, but the advantages of the DC motor is also its shortcomings, DC confidential generate the rated load, constant turnmoments of the performance, the armature magnetic field and the rotor magnetic field to be constant to maintain 90 °, it is necessary by the carbon brushes and commutator. Carbon brushes and commutator motor rotation will produce sparks, toner will cause damage to the components, using the occasion restricted. AC motor no carbon brushes and commutator, maintenance-free, sturdy, wide application, but the characteristics To achieve performance equivalent to the DC motor complex control technology to achieve. The modern semiconductor the rapid power components switching frequency to accelerate many to enhance the performance of the drive motor. Microprocessor speed is also faster and faster, can be achieved to control the AC motor is placed in a rotating two-axis orthogonal coordinate system, proper control of the AC motor in the two-axis current component, to achieve a similar DC motor control and comparable with the DC motor properties.

In addition, many microprocessor will control the necessary functions of the motor to do in the chip, and getting smaller; such as analog / digital converter is pulse width modulation, etc.. Brushless DC motor commutation electronic control of AC motors, DC motor characteristics similar to an application without missing on the institutions of the DC motor.

The brushless DC motor is a synchronous motor, and means that the rotational speed of the rotor by a the motor stator rotating magnetic field speed and rotor poles (p) of:

n = 120. f / p. , Changing the frequency of the stator a rotating magnetic field can change the rotational speed of the rotor in the rotor poles fixed cases. The brushless DC motor, synchronous motor with electronic control (drive), controlling the stator rotation frequency of the magnetic field and the rotor speed feedback to the control center repeatedly corrected, in order to achieve close to the characteristics of the DC motor. That brushless DC motor rated load range when the load changes can still control the motor rotor to maintain a certain speed.