AC Drives are devices for controlling motor speed by converting DC to AC. The emergence of AC Drives has improved productivity spectacularly and made a huge contribution to the development of the industry. Further, AC Drives have brought about a substantial change to our lives. For example, airflow from air-conditioners and fans can be regulated by changing motor speed. Thanks to AC Drives, we can keep a room at a comfortable temperature even in the hot summer and cold winter. The regulated airflow also reduces energy consumption, contributing to energy conservation. Yaskawa’s AC Drives are adopted in a lot of large-scale office buildings such as Roppongi Hills and Marunouchi Building.