Takao Hirasa

Expansion of operating limits for permanent magnet motor by current vector control considering inverter capacity

The current vector control method of PM (permanent magnet) motors is examined to expand the operating limits associated with inverter capacity. This control method is optimum in the sense of deriving maximum output torque within the voltage and current constraints. The effects of motor parameters are examined by computer simulation. The operating limits are greatly expanded by controlling the d- and q-axis components of the armature current according to the rotor speed. The operating limits are examined considering the demagnetization of the permanent magnet. If the permanent magnet has a straight demagnetization curve, like a rare-earth permanent magnet, the PM motor can be safely operated until the demagnetizing coefficient becomes 1.0. If wide speed range or constant power operation is desirable, a permanent magnetic with a high coercivity and a linear demagnetization curve must be used for the PM motor. >

Loss minimization control of permanent magnet synchronous motor drives

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 the 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. >

Servo drive system and control characteristics of salient pole permanent magnet synchronous motor

Permanent magnet (PM) synchronous motors fed by PWM inverters are considered. PM motors sometimes have a saliency, in which the q-axis inductance is larger than the d-axis inductance. A high-performance servomotor drive system for a salient-pole PM motor is described. 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 for the armature current vector is described, taking the demagnetization of the PM and the magnetic saturation into account. Characteristics such as torque, power factor, efficiency, power capability, transient responses, etc. are examined in detail by computer simulations and experimentally. >

Effects and compensation of magnetic saturation in permanent magnet synchronous motor drives

The effects of magnetic saturation are examined, and the compensation of magnetic saturation is proposed for the PM (permanent magnet) motor drives. A speed control system is established based on a DSP, and drive tests were carried out on a prototype IPM (interior permanent magnet) motor. The q-axis inductance of a IPM motor is found to vary depending on the q-axis current because of the magnetic saturation. The terminal voltage exceeds the maximum value in the flux-weakening region and, as a result, the transient responses sometimes become unstable because of saturation of the current regulator. The q-axis inductance is simply modeled as a function of the q-axis current and this compensated value of L/sub q/ is used in the control algorithm. The control performances are greatly improved by the compensation of magnetic saturation.<<ETX>>

Design and control system of inverter-driven permanent magnet synchronous motors for high torque operation

This work describes a current vector control method for permanent magnet (PM) synchronous motors suitable for high-torque operation. The current phase angle is controlled according to load conditions in order to use the reluctance torque effectively. Characteristics such as torque, efficiency, power capability and so on are greatly improved by this control method in 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, taking into consideration the inverter capacity. The tendency toward magnetic saturation and demagnetization of the permanent magnet is also examined. >

High performance servo drive system of salient pole permanent magnet synchronous motor

A high performance servomotor drive system is described for 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 permanent magnet and the magnetic saturation into account. Characteristics such as torque, power factor, efficiency, power capability, transient response, and so on are examined using computer simulations and experimental results.<<ETX>>

Expansion of operating limits for permanent magnet motor by optimum flux-weakening

The optimum flux-weakening control method of the permanent magnet (PM) motor is examined in order to expand the operating limits. The effects of motor parameters, such as d- and q-axis inductances, PM flux-linkage, and so on, are examined by computer simulation. Furthermore, the control method and the output characteristics are examined considering the PM demagnetization due to the direct axis armature reaction.<<ETX>>

Variable speed drive system of interior permanent magnet synchronous motors for constant power operation

Interior permanent magnet synchronous (IPM) motors can be applied to applications requiring constant power operation by means of the flux weakening control. The current vector control algorithm of IPM motors for constant power operation over the base speed is proposed. As the available voltage controlling the armature current vector is small in the flux weakening constant power region, the current vector sometimes becomes uncontrollable in transient operations because of the current regulator saturation. The high performance current regulator is also proposed to improve the current responses in the flux weakening region, which includes the decoupling current controller and the voltage command compensator. The control performances are confirmed by several drive tests with respect to the prototype IPM motor.<<ETX>>

Optimum values for magnet and armature winding thickness for axial-field permanent magnet brushless DC motors

When the motor thickness and the required starting torque are set for an axial-field permanent magnet brushless DC motor, the optimal ratio of the permanent magnet thickness to armature winding thickness is 2:1, because the copper loss of the armature windings is kept to a minimum. This conclusion is based on a new method in which such factors as loop resistance, a radial air-gap magnetic flux density approximated by curves of second order, and an experimental formula for the leakage coefficient are incorporated. The new method is also applicable to estimating torque, current, and input power at the start. These items can be more promptly estimated without a computer program, and physical insight is more easily gained by the aid of the new method than with a three-dimensional finite-element method. This is true even though the loop resistance and torque correction factor must be measured using a base motor. The calculated values of torque, current, and input power agree well with the measured values.<<ETX>>

Design and control system of permanent magnet synchronous motor for high torque and high efficiency operation

A current vector control method is described for permanent magnet synchronous motors for high torque and high efficiency operations. In this 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 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.<<ETX>>