General Purpose Permanent Magnet Motor Drive without Speed and Position Sensor

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 I 2 R 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. The AC induction motors have been widely used for industry applications. Across-the-line starting capability without Variable Frequency Drives (VFD) is a strong advantage of the induction motors. Usually motor price per output power ratio is lower than other motors. The squirrel cage induction motor is almost maintenance free except for the bearing part. The induction motor consists of a stator and a rotor. The rotating magnetic air gap flux is produced by three-phase AC voltage and stator flux distribution. The stator rotating flux and mechanical