High Torque BLDC Motor for Air Conditioning System

A major method for energy conservation of the air-conditioning system is to monitor the value of users' cold load and regulate the output of the air-conditioning system's refrigerating capacity. Through rotating speed regulation of the compressor, water pump and draught fan, the output of the air-conditioner's  refrigerating capacity can be regulated. This method to regulate the balance between supply and demand can improve the energy's utilization efficiency and avoid waste of the electric energy. In this way, how to control the rotating speed of the compressor, water pump and draught is a critical issue facing the air-conditioner's energy conservation.

For a long time, the electric motor used by the compressor, draught fan and water pump is mostly the AC asynchronous motor. There are many ways to regulate the speed of the AC asynchronous motor. The variable-frequency regulating speed technology is the most ideal one. In the early 1990s, the Japanese company Toshiba first adopted the frequency control of the AC asynchronous motor for the compressor control. Later, the variable-frequency regulating speed technology of the AC asynchronous motor started to find more and more applications in the central air-conditioning system.

Problems existing in the variable-frequency regulating speed technology

The variable-frequency regulating speed technology of the AC asynchronous motor, though having promoted development of the air-conditioner refrigeration technology, has been found with many defects.

1. The variable-frequency regulating speed technology cannot realize smooth speed regulation and the speed regulation scope is small. On the current market, the frequency-regulating grades of frequency converters range from five grades to ten grades. The frequency converter adopts the stair-type frequency modulation, so it can only realize the stair-type speed regulation rather than the smooth speed regulation.
   
   
2. In the process of variable-frequency speed regulation, the inductance loaded on the electric motor's circuit is changed, and many harmonic waves are thus generated, exerting an impact on the power grid and causing waste of the electric energy.
   
   
3. The electric motor has an ordinary efficiency. According to the data published by the United States Department of Energy, the motor efficiency in the AC asynchronous motor's variable-frequency speed regulating system is 85%.
   
   
4. In the process of variable-frequency speed regulation, if the motor's temperature rise is too high. It might cause waste of electric energy.
   
   
5. The variable-frequency speed regulating system has a poor dynamic performance and its speed variations are huge. The variable-frequency speed regulating process has changed the inductance of the electric motor, which might easily generate vibration and step-out when the load is changed. Therefore, it is a very unstable speed regulating system.

Use of the air-conditioning system with the high torque BLDC motor

In order to reach a higher requirement of energy conservation, an electric motor which is easier to control, and performs more steadily and efficiently can provide the air-conditioning system with the driving force. The high torque BLDC motor is a good choice. Adoption of the air-conditioning system with the DC electric motor (including the compressor, draught fan, and water pump) is easier to control and steadier to regulate the speed. With a larger scope of speed regulation, the BLDC motor is more efficient. The air-conditioning system with the BLDC motor has the following advantages:

1. Capable of realizing smooth speed regulation and wider in the speed regulation scope. The BLDC motor is easier to control and has a wider range of speed regulation. As a genuine continuously variable speed regulating system, it can freely adjust the refrigerating capacity output of the air-conditioning system.
   
   
2. In the speed regulating process, the nature of the load in the electric motor circuit is not changed, and the harmonic waves generated are just a few, which can cause little impact on the grid, thus being more energy-saving.
   
   
3. The electric motor's efficiency is high. The high torque BLDC motor can adopt the permanent magnetic to replace the electromagnet. According to the data published by the United States Department of Energy, the efficiency of the permanent magnet's BLDC motor can reach as high as 95%, which is 10% higher than that of the electric motor in the AC asynchronous electric motor's variable-frequency speed regulating system.
   
   
4. During the operation process, the temperature rise is slight, which is slower than the variable-frequency speed regulation of the AC asynchronous electric motor by around 20%.
   
   
5. Meanwhile, the speed-regulating system is highly reliable and has a high dynamic performance. The AC BLDC motor has a high reliability, and will not change the nature of the electric circuit during the speed-regulating process. The system can function more reliably.