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This paper aims to improve efficiency in permanent magnet synchronous (PM) motor drives. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the optimal control of the armature current vector. The control algorithm of current vector minimizing the electrical loss is proposed and the optimal current vector can be decided according to the operating speed and the load conditions. The proposed control algorithm is applied to the experimental PM motor drive system, in which one digital signal processor is employed to execute the control algorithms, and several drive tests are carried out. The operating characteristics controlled by the loss minimization control algorithm are examined in detail by computer simulations and experimental results.

The advantages of the conventional cylindrical linear pulse motor (C-LPM), which has a ring permanent magnet between the A- and B-phase stators, are its simple magnet shape and small motor diameter; the disadvantages are the thrust imbalance resulting from the magnetic flux path of the outer poles being longer than that of the inner poles. This thrust imbalance decreases the pull-in thrust and increases the positioning error. In this paper a new C-LPM with an interior permanent magnet mover which reduces this thrust imbalance is proposed. Steady and dynamic thrust are also examined and magnetic equivalent circuit is discussed. It is shown that a C-LPM with an interior permanent magnet mover effectively improves the thrust imbalance and the dynamic thrust.

This paper describes a current vector control method of permanent magnet synchronous motors (PM motors) for high torque operation. In this control method, the current phase angle is controlled according to load conditions in order to use the reluctance torque effectively. Several characteristics such as torque, efficiency, power capability and so on are greatly improved by this control on comparison with the conventional control method. The performance characteristics are greatly affected by the motor parameters which depend on the rotor configurations and permanent magnet geometries. The available maximum torque and power capability are also examined for the several types of PM motor considering the inverter capacity. The tendency toward magnetic saturation and demagnetization of permanent magnet are also examined.

Permanent magnet (PM) synchronous motors fed by PWM inverters are widely used for industrial applications. The PM motors sometimes have a saliency, in which the q-axis inductance is larger than the d-axis inductance. This paper describes a high-performance servo drive system of a salient-pole PM motor, in which an armature current vector is actively controlled according to load conditions in order to use a reluctance torque effectively, and as a result, a large torque can be produced. The control algorithm of the armature current vector is described, taking the demagnetization of PM and the magnetic saturation into account. The several characteristics such as torque, power factor, efficiency, power capability, transient responses, and so on are examined in detail by the computer simulations and experimental results.