The utility of Brushless DC Motor

Nowadays air conditioner and gas water heater have become the necessities in people’s life. As we all know, the motor that was used in air conditioner and water heater earlier is AC induction motor. First, this motor has obvious shortcomings, low efficiency, high energy consumption, which is clearly contrary to the trendy of today's low-carbon environmental protection, energy saving and carbon emission reduction. Secondly, no matter air conditioner or gas water heater, either needs different volume of air in different circumstances. If you want to do this function, you need to use a VVVF type of inverter which mainly depended on imports, so the price is high. To make some great strides in technological innovation, some manufacturers changed AC induction fan in the air conditioning and water heater to dc brushless motor. Comparing to the AC induction motor, the controlling air flow method of brushless blower is much simpler and has higher precision control.
Due to the elimination collector ring and brush for excitation, the structure of brushless DC motor is greatly simplified. Not only improve the procession of motor, but also, the motor running mechanical reliability is greatly enhanced and life is also increased. Meantime, Flux density can greatly improve motor indicators to achieve the best design; its direct effect is to cause motor smaller and lighter.
Moreover, compared to other motors, BL dc blower motor also has excellent controlling performance. This is because:
First, due to permanent magnet material high-performance, the motor torque constant, the torque inertia ratio and power density is greatly improved. Rational design also enables running inertia, electrical and mechanical time constant time greatly to reduce; all these datas, as the main indicator of the servo control performance, has been greatly improved.
Second, modern permanent magnetic circuit design is more perfect, together with the high coercivity of permanent magnet materials, greatly enhance anti-armature reaction and its resistance to demagnetization of the permanent magnet motor, motor control parameters effect with external disturbing is greatly reduced.
Third, due to electrical excitation replaced by permanent magnets, reducing the design of the excitation winding and the excitation magnetic field, thus reducing the magnetic field flux, the inductance of the excitation winding, the magnetizing current and many other parameters, and thus directly reducing the controllable variables or parameters. All in all, the permanent magnet motor has excellent control ability.
Third, The characteristics:
1. Low loss, high efficiency
Because of using permanent magnet excitation, eliminating the loss of the induction motor excitation current generated; Meantime, PM BL DC motor run synchronously and eliminate the induction motor rotor core conversion loss. These two aspects make the efficiency of BL DC motor is much higher than induction motor, especially small capacity motor efficiency is increased obviously.
2 High power factors
Due to the excitation magnetic filed of the brushless DC motor does not require reactive power current, the power factor is much higher than the induction motor, brushless DC motor can run at power factor 1, this is extremely beneficial for small power motor. Compared to the induction motor, Brushless motors owns higher efficiency at loading working , also have more advantage in light load.
3. Excellent speed adjusting performance, simple control
Compared with the variable frequency control of induction motor, speed control for brushless DC motor is not only simple, but also has better speed performance.
4 Long life
Brushless DC motor life primarily depends on the bearings used in the motor. Such as the selection of high-quality bearings, motor life can reach up to 20,000 hours or more.
5 The capacity of the inverter is low; therefore cost of inverter is low.
The brushless DC motor requires a rectangular-wave current, the rated current in the continuous operation of the inverter refer to the peak value of the rectangular wave. The induction motor requires a sine wave current. Rated current in the continuous operation of the inverter generally refers to a sine wave. In order to maintain the ability to inverter controlling the motor current, there should be a sufficient gap between the DC voltage of the inverter and the motor induced electromotive force. Therefore, the peak of the trapezoidal wave of brushless DC motors and induction motor sine wave induced electromotive force is both limited by the DC voltage of the inverter. If peak current of BL dc brushless motor and induction motor is equal, the output power of BL DC motor is higher 33% than induction motor, that is to say, one same rectifier / inverter can drive BL dc motor which output power is higher 33% than induction motor.
To sum up, brushless DC blower will completely replace the AC induction motor in the air conditioning and gas water heater. Moreover, with the technical advances, brushless DC motors is also applied in household appliances, automobiles and office equipment and other fields.