A motor control device has: a motor current detecting portion for detecting, based on a current flowing between an inverter that drives a three-phase motor and a direct-current power supply, a motor current flowing through the motor; a specified voltage value producing portion for producing, based on the motor current, a specified voltage value as a target value for a voltage to be applied to the motor, and outputting the specified voltage value thus produced; a specified voltage value holding portion for holding an earlier specified voltage value outputted from the specified voltage value producing portion; and a specific period setting portion for setting a specific period based on a voltage difference between two of U-phase, V-phase, and W-phase voltages of the motor. Outside the specific period, the motor is controlled via the inverter based on the specified voltage value outputted from the specified voltage value producing portion, and, within the specific period, the motor is controlled via the inverter based on the specified voltage value held by the specified voltage value holding portion.

Motor control device

Thermal models used in overload protection relays often fail to predict the rotor temperature for motors with impaired cooling conditions. In this case, the temperature estimated from the rotor resistance can be used as an indicator of the motor's cooling capability. However, this estimated rotor temperature is often corrupted by estimation error due to the asymmetry in the power supply. A detailed analysis of the trajectories of the complex current and voltage space vectors in a synchronous reference frame is presented in this paper, and the negative sequence fundamental frequency components are identified as the major cause of the estimation error. Based on this analysis, a fast and efficient algorithm is proposed to calculate the rotor temperature for line-connected induction machines. By applying the Goertzel algorithm to the complex current and voltage space vectors, constructed directly from the motor terminal measurements, the positive sequence fundamental frequency components are extracted, and the rotor temperature is then estimated with significantly reduced estimation error. Compared to the conventional scheme based on the fast Fourier transform, the proposed algorithm is faster and more efficient, and is therefore more suitable for implementation on a low-cost hardware platform.

A Complex Space Vector Approach to Rotor Temperature Estimation for Line-Connected Induction Machines With Impaired Cooling

PROBLEM TO BE SOLVED: To obtain a motor drive device that executes demagnetization protection with high accuracy, while executing high-efficiency drive and high-speed overload operation, when executing motor drive by switching between star connection and delta connection, and to provide a motor drive method and a refrigerating and air-conditioning device. SOLUTION: An inverter control part 30 switches wire connection of a motor 11, by controlling wire-connection switching relays 21a-c, 22a-c that switch stator windings 15a-c of the motor 11 to either of star connection and delta connection on the basis of either of a frequency command and an external switching signal. A CPU 31 sets a motor constant matched with a wire-connection specification after switching and at least one of an overcurrent protection level and an abnormal voltage protection level, on the basis of an inverter output current and a DC bus-bar voltage that are detected by a current detection element 3. A PWM generating means 32 subjects an inverter main circuit 2 to PWM control, on the basis of the motor constant and the overcurrent protection level or the abnormal voltage protection level that are set by the CPU 31. COPYRIGHT: (C)2008,JPO&INPIT

Motor drive device and driving method, and refrigerating and air-conditioning device

A vector control method is provided for controlling a rotor speed of an induction motor by an inverter which provides an AC current of varying frequency to the induction motor, and a vector controller which provides control voltage Vu, Vv, Vw, in response to an excitation current command i1d*. The excitation current command is indicative of an excitation current being fed to the induction motor, a desired rotation speed command ωr*, and a primary frequency ω, for controlling the inverter to vary the rotor speed. The method includes the steps of detecting a primary current being fed to the induction motor, analyzing the detected primary current to obtain an excitation current i1d and a detected torque current i1q, multiplying a torque value represented by the detected torque current i1q by a predetermined motor constant Km to obtain a slip frequency ωs, and adding the obtained slip frequency ωs to the rotation speed command ωr* to determine the primary frequency ω (ω=ωr* +ωs), calculating a deviation between the delay torque current i1q, and the detected torque current i1q and supplying the deviation to a proportional plus integral controller, the proportional plus integral controller producing as an output an updated delayed torque current i1q, as the torque value for determining the primary frequency ω.

Vector control method for controlling a rotor speed of an induction motor

A control apparatus for controlling an electric vehicle, electric car, rolling stock and electric locomotives, which ensures that an inverter output frequency command for its inverter will not depend on the rotor frequency of the induction motor, but controls the inverter output current using a constant current control system, thus preventing an overcurrent, and is capable of accelerating or decelerating the vehicle at a torque precisely corresponding to a current command The inverter output frequency command is incremented or decremented in accordance with a frequency-to-time rate-of-change command which has been updated by the current control system Since the inverter output frequency command is adapted basically not to depend on the rotor frequency of the induction motor, and since the output current of the inverter is controlled by the constant current control system, there are such advantages according to the invention that an overcurrent is not likely to occur, and the vehicle can be accelerated or decelerated at a torque precisely corresponding to the current command

Control Apparatus for Electric Vehicles

An error current component which becomes zero when an actual value of a primary flux coincides with a set value inducted by a product of an exciting current command and a primary self-inductance by detecting a primary current of an inductance motor, is inducted by an error current component processing circuit. A primary resistance compensation circuit processes a compensation amount of a primary resistance compensation amount. And a compensation voltage processing circuit processes a compensation voltage which directs the error current component to zero. A rotating speed of the induction motor can be controlled in a stable state even though a value of primary resistance of the induction motor is varied by temperature. Further, inadequate torque and excess current can be avoided.

Masato c

Papers

Controller for induction motor