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Large PMSM fans are very beneficial, and they are essential for large and small spaces. They provide healthy and fresh air in the area. Many factories, shopping malls, farms, libraries are using large commercial fans; therefore, they are in demand. You can also get an HVLS fan for a small space, there are different sizes available for different places. Manufacturers are trying new and more advanced technologies. PMSM fan is also a new technology that is still in improvement stages. It has its advantages and disadvantages. So, we will discuss all the disadvantages of this new technology. But before getting into the disadvantages, we would like to discuss PMSM fans.
What are PMSM fans?
PMSM fans are large commercial and industrial ceiling fans that use the Permanent Magnet Synchronous Motor. While old technologies include BLDC and Induction motors. PMSM is a special type of synchronous motor that has a permanent magnet in it. A conventional synchronous motor requires an AC supply on its stator winding and DC supply for the excitation. But the PMSM requires only AC because the work of DC supply is done by permanent magnets. Therefore, PMSM is easy to use as compared to conventional synchronous motors. You don’t need an extra DC power source for it. The AC supply is provided on the stator and the permanent magnets are on the rotor.
PMSM motors have several advantages over other motors. They have high speed at a low noise level. The heat transfer is also better, and the cooling system is simple. They do not require maintenance at all; there is no need for lubrication or any other maintenance work. These can be installed in smaller places as well; thus, they are suitable for both industrial and commercial applications. PMSM fan is an excellent fan for small space. These are the reasons that PMSM fans are getting more attention. RTFANS make PMSM fans, the fans are available in different sizes. The sizes are from 7.3m (24ft) to 3.7m (12ft). These fans can cover a large area up to 1800 cubic meters. The power of the motor is around 1.2-1.5kW depending on the size. These are noiseless fans and we are still trying to make improvements in them. Our researchers and teams are testing the fan according to international standards.
Disadvantages of PMSM Fans
PMSM fans have some disadvantages because they are in the initial phase. Let’s discuss the disadvantages.
The first disadvantage of PMSM fans is the cost. They are much more costly as compared to other types of large commercial and industrial fans. As we know that PMSM requires permanent magnets and their performance is also based on the quality of the magnet. If you are using high-quality magnets, then the fans will perform excellently. The material of the magnet should have excellent flux density and it should magnetize easily. The magnets with the desired features are rare and expensive. Researchers select the best material and try it to get the best performance. The materials that can be used as magnets are Neodymium Iron Boride (NdFeB) and Samarium Cobalt (SmCo). These have excellent flux density, but they are costly.
Researchers are still finding the best and cost-effective material for making a permanent magnet. But for now, these fans are very expensive due to the use of rare-earth magnets. We hope in the future, these will be cost-friendly and much better than other HVLS fans.
2. Irreversible Demagnetization
This is a problem in PMSM. These motors use permanent magnets, and everything depends on the magnetization of the magnets. Due to any problem in magnetization, the fan will not perform well or stop. These motors undergo irreversible magnetization due to changes in temperature. At extreme low and high temperatures, the magnets are irreversibly demagnetized. Extreme temperature can be one cause, but irreversible demagnetization can also occur due to an external magnetic field. Although the presence of an external magnetic field is rare, it can affect the motor if it is present. The fan should operate in normal conditions without any problem.
Due to irreversible demagnetization, the performance degrades. It even becomes unstable in some cases. This problem is still a research topic and researchers are trying to overcome it. RTFANS are trying to overcome it through research and constant work.
3. Demagnetization Due to Ageing
Demagnetization also occurs due to aging. If you are not using the recommended material for magnets, then it will soon demagnetize due to aging. Otherwise, high-quality expensive magnets work for a long time, but they are also prone to this problem.
4. Complex Control
Controlling a PMSM is not that easy as other motors. It requires a complex controlling system. There are two methods of controlling a motor which is controlling the armature current and controlling the field current. There is only one source in PMSM which is AC supply on the stator. While the rotor does not have any supply, so you cannot control the speed using the rotor with ease. The only way to control the motor is by controlling the AC supply on the stator. This needs a complex control system including power electronics and microcontrollers. It is possible to control the motor, but it is not simple. Moreover, it is expensive as well. These motors cannot be effectively controlled by using conventional Digital Signal Processors (DSPs) and old methods of controls such as PID and adaptive control. Now latest methods such as vector control techniques are used to control PMSM.