Electricity: motive power systems – Synchronous motor systems
Reexamination Certificate
2002-03-15
2004-01-13
Masih, Karen (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
C318S701000, C318S800000, C318S799000, C318S811000
Reexamination Certificate
active
06677724
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a permanent magnet type AC synchronous motor including a linear and a rotary motor, wherein initial magnetic poles of the AC synchronous motor are estimated without using a magnetic pole sensor (pole sensor).
BACKGROUND ART
Information on an initial magnetic pole position detected from a magnetic pole sensor is required when an AC synchronous motor is started, such that the AC synchronous motor operates in accordance with commands based on correct information on a detected initial magnetic pole position. There may arise such problems as when the information on the detected initial magnetic pole position shifts from the magnetic pole position of the AC synchronous motor by ±90 degrees, no torque is generated so that the AC synchronous motor does not operate, and when the shift exceeds ±90 degrees, the AC synchronous motor reversely rotates as opposed to a command. From such reasons, the correct information on a detected initial magnetic pole position is critical in the AC synchronous motor, so that a variety of initial magnetic pole estimating methods have been devised for AC synchronous motor in order to acquire correct information on a detected initial magnetic pole position. A relationship between an offset angle of an initial magnetic pole position and a generated torque (hereinafter, a thrust force of a linear motor is also shown as a torque) is represented by Equation (1) and shown in FIG.
16
.
T=Tm
×cos(&thgr;error) (1)
where T is a generated torque, Tm is a maximum value of the torque, and &thgr;error is an offset angle of the initial magnetic pole position.
A prior art technique described in Japanese Patent Laid-Open No. 153576/1994 applies a voltage corresponding to an arbitrary initial magnetic pole position angle to estimate the initial magnetic pole position from information on a rotating direction and a rotational speed of a motor at that time. This initial magnetic pole estimating method repeats the estimation to find a correct initial magnetic pole position.
However, the prior art technique involves a repetition-based trial and error method which approaches from a wide estimation error range to a narrower estimation error range of the initial magnetic pole position to estimate a true value for the initial magnetic pole position of an AC synchronous motor, and experiences the following problems:
(1) a correct initial magnetic pole position cannot be estimated (a magnetic pole position estimation accuracy range is within ±30°);
(2) a motor operation range can become wider during an estimation of an initial magnetic pole position;
(3) an estimation time can be long; and
(4) an application to a load is difficult if disturbance such as a large static friction, cogging and the like exists in the load.
To solve the foregoing problems, it is an object of the present invention to make full use of the performance and characteristics of an AC synchronous motor by:
(1) the ability to estimate a magnetic pole position in a short time;
(2) the ability to freely set a range in which the motor can operate;
(3) the ability to minimize a range in which the motor can operate;
(4) the applicability to a load even if disturbance or large cogging torque exists in the load; and
(5) the ability to correctly estimate a true value for an initial magnetic pole position.
DISCLOSURE OF THE INVENTION
The gist of an initial magnetic pole estimating apparatus for an AC synchronous motor according to the present invention lies in the following (1)-(32).
(1) An initial magnetic pole estimating apparatus for an AC synchronous motor, equipped in an AC synchronous motor controller comprising speed control means for calculating a command torque (command current) from a command speed, current control means for driving the AC synchronous motor in accordance with the command torque (command current), and a PWM power converter, wherein the initial magnetic pole estimating apparatus is characterized by having speed deviation calculating means for subtracting the detected speed from the command speed generated by command speed pattern generating means to calculate a speed deviation, a speed gain control unit for multiplying the speed deviation by a speed gain to calculate a command torque (command current), mode section determining means for determining a mode section (a first cyclic section and a second cyclic section) from the command speed, a mode switch for switching a mode section to any of the first cyclic section and the second cyclic section in accordance with a result in the mode section determining means, data acquisition speed section determining means for determining whether the command speed is in a data acquisition speed section when the first cyclic section is selected, a first command torque calculating means (first command current calculating means) for calculating first command torque data (first command current data) from the command torque (the command current) in the determined data acquisition speed section, data acquisition speed section determining means for determining whether the command speed is in the data acquisition speed section when the second cyclic section is selected, second command torque calculating means (second command current calculating means) for calculating second command torque data (second command current data) from the command torque (the command current) in the determined data acquisition speed section, and estimated initial magnetic pole calculating means for calculating an estimated initial magnetic pole position using information on the first command torque data (the first command current data) and the second command torque data (the second command current data).
(2) An initial magnetic pole estimating apparatus for an AC synchronous motor equipped in an AC synchronous motor controller comprising PWM power converting means for converting a direct current voltage to an arbitrary alternate current voltage to drive the AC synchronous motor, three-phase current detecting means for detecting a three-phase current of the AC synchronous motor, an electric angle detecting means for detecting a relative electric angle of the AC synchronous motor, three-phase/two-phase coordinate conversion calculating means for performing a three-phase/two-phase coordinate conversion from a detected three-phase current to a detected two-phase current using the detected electric angle, detected speed calculating means for calculating a detected speed from the detected electric angle, two-phase current error calculating means for subtracting the detected two-phase current from a two-phase command current comprised of a q-axis command current and a d-axis command current to calculate a current error, a two-phase current proportion integration control unit for multiplying the current error by a two-phase current proportion integration gain to calculate a two-phase command voltage, two-phase/three-phase coordinate conversion calculating means for performing a two-phase/three-phase coordinate conversion from the two-phase command voltage to a three-phase command voltage using the detected electric angle, and PWM gate pulse calculating means for comparing the three-phase command voltage with a carrier waver to calculate a PWM gate pulse and outputting the PWM gate pulse to the PWM power converting means, wherein the initial magnetic pole estimating apparatus for an AC synchronous motor is characterized by having default initial magnetic pole setting means for setting a default initial magnetic pole position to zero, command speed pattern generating means for generating a command speed as a two-cycle waveform, speed deviation calculating means for subtracting the detected speed from the command speed to calculate a speed deviation, a speed gain control unit for multiplying the speed deviation by a speed gain to calculate a command torque (command current), mode section determining means for determining a mode section (a first cyclic section and a second cyclic section) from the command speed, a
Kim Tae-Woong
Watanabe Jun-ichi
Kabushiki Kaisha Yaskawa Denki
Masih Karen
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