Development direction of permanent magnet synchronous motor in HVAC industry

It is the eternal demand and desire of the whole HVAC industry to promote innovation and create new products and ideas that can redefine the market. In the field of motor, permanent magnet synchronous motor (PMSM) is an infinitely possible choice, which has aroused strong concern in this field.

According to Tim Schamel, vice president and general manager of Nippon Denso Electric Co., Ltd., PMSM is an AC synchronous motor, and its excitation is provided by permanent magnets. These motors usually have sinusoidal back electromotive force waveforms. The rotor assembly is equipped with a permanent magnet, surrounded by three equally spaced windings, which are fixed to the stator assembly. Then torque is generated by attraction or repulsion between the stator field and the magnetic field of the rotor.

PMSM is also widely called electronic commutation motor in industry.

Brent Boyd, director of Emerson's commercial and residential solutions, said that PMSM is in sharp contrast to common induction motors because they have to energize the rotor and stator to generate a magnetic field in the motor. Therefore, PMSM usually requires less work and is more efficient.

Application field of PMSM

At present, PMSM is most commonly used in high efficiency systems. Katrina Krites, the variable-speed marketing manager of Emerson's commercial and residential solution air conditioners, said that there are compressors, high-efficiency condenser fans, indoor fans, geothermal energy and water pumps currently on the market.

The efficiency advantages provided by these motors mean that they can provide value to multiple market segments.

"PMSM provides energy-saving alternatives for manufacturers, contractors, end users and homeowners," Schamel said. "These products consume very little energy, especially when multiple motor speeds or variable speed performance are required. These products also help manufacturers and contractors meet the requirements of the US Department of Energy (DOE) regulations-Energy Star and the energy consumption targets required by utility discounts. "

In this field, the current PMSM design of electric motors is suitable for residential applications, including indoor applications, such as furnaces and air handlers, and outdoor applications of air conditioners and heat pumps.

"Constant airflow is the advantage of No.1 air conditioning system. Because of the internal working principle of the motor, it can provide constant airflow under various conditions," Schamel said. "By using software algorithms that can be adjusted by the OEM, the motor provides what it is told to provide, not more or less, but just right. This means that due to the system changes in the structure of domestic or commercial piping system, there is no blowing at the lower static state and no flow loss at the higher static state. You can get what you need from a compact direct-drive blower, so as to achieve consistent temperature control to the maximum extent. In addition, the power usage of the motor is only necessary to meet the needs of the HVAC system.

Development forecast of PMSM

Due to the forecast that the motor market will grow strongly in the next five years, manufacturers are excited about the development of PMSM.

"We expect PMSM to continue to grow in the next few years, partly to meet the efficiency supervision requirements of commercial and residential space," Boyd said.

Krites added that all major system manufacturers have advanced products using PMSM technology. "With the change of technology and the reduction of cost, it makes the application of PMSM easier, so we expect PMSM to be more widely adopted." She said.

Schamel also expects that the DOE rules for residential and commercial HVAC equipment can promote demand, and end users and utilities are interested in reducing energy consumption, thus increasing the popularity of PMSM.

In fact, DOE recently issued the final regulations on the certification, compliance, labeling and implementation of electric motors and small motors. According to the US Department of Energy, it is being revised to meet the requirements of certification, compliance and enforcement departments for all other covered products and equipment. The regulations adopted in this rule also provide specific sampling plans, certification requirements, methods for determining alternative efficiency, and implementation regulations for motors and small motors.

"The U.S. Department of Energy's rules have really raised people's interest and awareness of these products," Schamel said. "This increased awareness not only enables people to better understand the energy-saving potential of these designs, but also increases the benefits of improving temperature and humidity control, reducing sound level, consistent airflow and better filtration, and other benefits."

Boyd pointed out that PMSM technology is also expanding to niche and transportation applications. "In addition, faster microelectronics and more efficient drivers may increase the adoption rate by reducing the cost," he said. "Considering the additional cost of efficiency, there may be restrictions on where this technology can be adopted in the future."

An interesting focus of PMSM in the future may be to increase people's attention to cost and supply of rare earth magnets. Schamel said that one advantage of PMSM is that they can work with ferrite magnets.

"The main disadvantage of ferrite magnets is that when magnets are mounted on the surface of the rotor assembly, they do not generate as much magnetic flux density as rare earth magnets, which leads to lower torque density." The next generation PMSM developed by Nidec for HVAC industry will adopt spoke rotor technology. This new rotor technology uses low-cost ferrite magnets and tends to have a higher torque density than conventional surface-mounted rotor assemblies, which results in a lower-cost motor construction.

However, the technology itself will continue to change and develop, and customers' awareness of this product is also changing.

"In addition to reducing energy consumption, these products also have variable speed capability and can achieve other advantages, including consistent temperature control, improved humidity control, lower sound level, consistent airflow and better air filtration." All these benefits will promote the continuous growth of PMSM.

"PMSM technology has existed for quite a long time, and it is more and more widely used in HVACR industry," Krites said. "OEM understands this technology and has used it in fans and compressors for many years. Contractors realize the benefits of efficiency and like advanced diagnosis more and more, but they don't seem to know much about the actual technology itself.