Introduction to DC fans
DC fans currently use DC brushless motor, brushless DC motor due to eliminating the excitation of the collector ring and brush, the structure greatly simplified. At the same time not only improve the motor process, and the mechanical reliability of the motor running greatly enhanced life expectancy.

At the same time, the air gap magnetic density can be greatly improved, the motor index can achieve the best design, the direct effect is the motor volume reduction, weight reduction. Not only that, but also has excellent control performance compared to other motors. This is because: First, due to the high performance of permanent magnet materials make the motor torque constant, torque inertia ratio, power density greatly improved. Through the reasonable design and can make the inertia, electrical and mechanical time constant and other indicators greatly reduced, as the servo control performance of the main indicators have been greatly improved. Second, the design of modern permanent magnet magnetic circuit has been more perfect, coupled with the permanent magnet material coercivity is high, so the permanent magnet motor anti-armature reaction and its ability to greatly reduce the anti-demagnetization, motor control parameters with the external Disturbance effects are greatly reduced. Third, due to the use of permanent magnets to replace the electric excitation, reducing the excitation winding and excitation magnetic field design, thus reducing the excitation flux, excitation winding inductance, excitation current and many other parameters, which directly reduces the controllable variables or parameters. The above factors can be said that the permanent magnet motor has excellent controllability.

At present, many large-capacity fan adjustment air flow has been a lot of frequency control mode, this type of inverter is mainly dependent on imports, expensive. At present, the power rating of 1kw below the fan, especially the home air conditioner and other fans have permanent magnet brushless DC motor drive, and the use of speed regulation mode. 1 ~ 10kw power range of the huge amount of fan, the basic use of induction motor drive, and adjust the air opening way to adjust the air volume. For this power range of the fan, the use of permanent magnet brushless DC motor drive to replace the original induction motor drive has great advantages.

Features of DC fans
(1) loss of small, high efficiency
Because the use of permanent magnet excitation, eliminating the induction motor excitation current loss; the same time permanent magnet brushless DC motor work in synchronous operation mode, eliminating the induction motor rotor core frequency loss. These two aspects of the permanent magnet brushless DC motor operating efficiency is much higher than the induction motor, small-capacity motor efficiency is more obvious.

(2) high power factor
As the brushless DC motor excitation magnetic field does not require the reactive current of the grid, so the power factor is much higher than the induction motor, brushless DC motor can run on a power factor, which is very favorable for low-power motor. Brushless motors have a higher efficiency and power factor than rated motors, and are more advantageous at light loads.

(3) speed performance, control is simple
Compared with the induction motor speed control, brushless DC motor speed control is not only simple, but also has better speed performance.

(4) inverter capacity is low, so the inverter cost is low
Brushless DC motors require rectangular wave current, and the current rating at which the inverter continues to operate is the peak of this rectangular wave. Induction motors require sine wave current, the current rating of the inverter running continuously refers to the effective value of this sine wave. In order to maintain the inverter on the motor current control capability, inverter DC voltage and motor induced electromotive force should have enough difference between. So brushless DC motor trapezoidal wave induced electromotive force and induction motor sine wave induced electromotive force can reach the peak voltage are limited by the inverter DC voltage. In this case, if the peak of the brushless DC motor and the induced motor current is assumed to be equal, the former power output is 33% higher than the latter, that is, the same rectifier / inverter can drive more than the induction motor output Power 33% higher than the brushless DC motor.