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Inverters Control the Motor Inverters Inverter technology made its mark on the history of air conditioners by ushering in a new era of comfort and energy saving

Daikin has always striven to be the industry’s leader in technological advancement. Just how does Daikin By switching the direction of the electric current create technology second to none? This first in a series of to the electromagnet, the N and S poles can be feature articles on core technologies spotlights the inverter, switched to generate the attractive force and repulsive force naturally existing between two which has become synonymous with the name Daikin. magnets. Inverters can control motors by using these two forces alternately at the right timing. The inverter is like a motor driver which controls the air conditioner compressor’s motor

A reluctance DC motor has a rotating internal spindle. An air conditioner is made The spindle is embedded up of an indoor unit and an with a strong neodymium outdoor unit. The inverter magnet to make it a high- is located in the outdoor power magnet. To rotate unit. It controls the motor the motor, the N and S of the compressor, which poles of the electromag- is really the heart of the net are switched at high machine. speed. The inverter is what controls this process.

Before diving into inverter tech- reaches a set temperature. The motor nology, let’s review the basics of air restarts when the room tempera- conditioning design and electricity. ture falls below the set temperature, Air conditioners have an outdoor and repeats this cycle. This type of current back to alternating current of electronics technologies as a and comfort. ’s first inverter unit and an indoor unit, with a heat operation causes large fluctuations in was called a inverter, but in , critical issue and begun inverter air conditioner, for example, boasted pump to transfer heat between these temperature and wastes energy. the device to control the entire pro- research without leading to com- minimal temperature fluctuations by units. With these main parts, an air The goal is to maintain a constant cess is commonly referred to as an mercialization. Daikin released its eliminating unevenness. While this conditioner provides both heating and room temperature and save energy inverter. Simply put, the inverter is first inverter air conditioner model in offered a higher level of comfort, it cooling. The heart of the machine is at the same time. To do this, the the motor driver which controls the 1984. Toshiba, meanwhile, launched did not prioritize energy saving. the compressor, located in the outdoor revolution speed can be lowered to a motor by adjusting the frequency and the first inverter-type residential If the inverter was to be the driver unit. Refrigerants in the compres- level needed to maintain room tem- other aspects of operation. air conditioner three years earlier. for the motor, then a high perfor- sor are used to transfer heat. They peratures instead of switching the Here is the history of the devel- Daikin’s inverter, however, was mance inverter would need to be attain a state of high temperature motor OFF when a set temperature is opment of the reluctance DC tech- made by an external company. The coupled with a high performance and pressure when compressed. In reached. For this type of operation, nology* and its DC inverter which birth of Daikin’s own reluctance DC motor. At the time, however, Daikin cold climates, cold refrigerants are the air conditioning system needs propelled Daikin to the fore of the air technology would have to wait until didn’t have a single engineer capable compressed by the compressor to a to variably adjust motor frequency, conditioning industry, as well as some Kazunobu Ohyama (currently TIC of developing a motor from scratch. high temperature and pressure, then which is synchronized with the revo- insight into the DNA behind “Daikin, Executive Engineer), who had been Ohyama rooted out applicable sent to the indoor unit to provide lution speed. The Technology Company.” pursuing research into the technology, research papers from journals around warm air. When raising room tem- One of the immediate problems, Eyeing the IPM motor joined the company. the world and took part in academic conferences to gain insights into peratures quickly, the compressor’s however, is that power supply at despite a lack of motor In 1989, Daikin had just wound revolution speed is increased, which factories and households is alternating down its Ideal Inverter Air condi- development options. Kazunobu Ohyama engineers raises the refrigerant temperature Executive Engineer, current, which has a fixed voltage and tioner (IIA) project and was ready to Ohyama’s search came to fruition faster and sends heat to the indoor Technology and Innovation Center frequency. This makes it necessary to The history of Daikin’s full-scale start technology development for the with the IPM motor. The IPM motor Motor Inverter Technology and Utilization unit. The motor driving the compres- Senior Associate Officer change the current to direct current, development of inverter air condi- next-generation of air conditioners. had a unique structure in which the

sor accounts for 90% of an air condi- Born in Kagawa Prefecture in 1956, he later graduated and then change it back to alternat- tioners dates back to 1980 with the Ohyama joined the company in 1986 rotating rotors, made of electromag- tioner’s total energy consumption. from Tokyo Institute of Technology Master’s Program ing current. That’s the basic concept establishment of the Electronics as a researcher at the Electronics netic steel plate, were embedded with in 1981. He joined Daikin in 1986 after working as Conventional air conditioners turn an assistant at Nagoya Institute of Technology’s behind the inverter. The technology Engineering Center at the Shiga Plant Engineering Lab. After fully research- magnets. In conventional motors, the motor ON or OFF. When turned Department of Electrical and Electronic Engineering. In to change alternating current to direct (formerly the Electronics Engineering ing consumer needs, he determined the magnets cover the surface of the 2004, he was promoted to Associate Officer of Daikin on, the motor operates at 100% speed, Environment and Air Conditioning R&D Laboratory, Ltd. current was called a converter, and Lab). Even before that, the company that the next-generation air condi- rotors, meaning the motor can only then stops completely when the room and then assumed his current position in 2015. the technology to convert the direct had recognized the strengthening tioners needed both energy saving utilize the attractive force (magnetic

*Reluctance DC technology: Technology associated with reluctance DC motors. Reluctance motors are unique in that the magnets embedded in the rotor endow them with a unique electromagnetic 20 Challenge 2016 Vol. 01 structure. With this structure, the motor can effectively utilize magnetic torque and reluctance torque (attractive force between the iron and magnet), thereby reducing electric usage by a significant degree. 21