1. Power consumption by electric motors
Worldwide, about two-thirds of the electricity is consumed by motors used in powers industrial facilities. According to DOE report, the motor systems are responsible for 63% of all electricity consumed by U.S. industry and electric bill represents more than 97% of total motor operating costs.
Rapidly increasing energy cost and strong global interest in reducing carbon dioxide emissions are encouraging industry to pay more attention to high-efficiency motors.
Permanent Magnet (PM) motors have higher efficiency than induction motors because there are no I2R losses of the rotor. But widespread use of the PM motors has been discouraged by price and requirement of a speed encoder.
Recent release of low-cost high-performance CPUs and establishment of the speed sensorless control theory (hereinafter referred to as an open-loop vector control method) enables the advent of a general-purpose open-loop control PM drive. In this white paper, the open-loop PM motor control technology is introduced and its characteristics and major application fields are described.