Electricity: motive power systems – Synchronous motor systems
Reexamination Certificate
1999-11-19
2001-06-05
Masih, Karen (Department: 2837)
Electricity: motive power systems
Synchronous motor systems
C318S727000, C318S809000, C318S608000, C318S799000
Reexamination Certificate
active
06242882
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a motor control apparatus for inferring the position of a magnetic pole of a synchronous motor rotor and controlling the synchronous motor in accordance with the inferred position of the magnetic pole.
A conventional technology adopted in a motor control apparatus for inferring the position of a magnetic pole of a synchronous motor is disclosed in Japanese Patent Laid-open No. Hei 7-245981.
According to description in Japanese Patent Laid-open No. Hei 7-245981, a component of a current vector or a voltage vector parallel and perpendicular to an alternating voltage vector or an alternating current vector applied to a salient pole synchronous motor is detected, from at least one of the components, a phase difference angle formed by the applied vector and a magnetic flux axis is calculated and the position of a magnetic pole is inferred from the calculated phase difference angle.
This technique offers the benefit that the position of a magnetic-pole can be inferred without letting the synchronous motor generate a torque since the alternating voltage is applied to the magnetic flux axis.
SUMMARY OF THE INVENTION
However, the prior art described above has the following problem.
In the technology disclosed in Japanese Patent Laid-open No. Hei 7-245981, an alternating voltage vector or an alternating current vector is applied to an orthogonal axis coordinate system having two axes perpendicular to each other set in a motor control apparatus, a current vector or a voltage vector generated thereby is detected and the position of a field pole is computed. Formulas used in the computation are based on voltage/current equations of the synchronous motor, requiring operations such as differentiation and division. As a result, the computation time is very long and, in addition, deterioration of accuracy in the inference of the position of the magnetic pole due to parameter errors is conceivable.
It is thus an object of the present invention to provide a motor control apparatus having a means for inferring the position of a magnetic pole of a synchronous motor with a high degree of accuracy by adopting a simple method, that is, a method that allows the means to infer a position in a short period of time.
In order to achieve the object of the present invention described above, there is provided a motor control apparatus having a magnetic pole position inferring means for inferring the position of a magnetic pole of a synchronous motor by applying an alternating-current (AC) current signal for inference use or an AC voltage signal for inference use in the direction of one of two mutually perpendicular axes of an orthogonal axis coordinate system and detecting a current or a voltage in the direction of the other of the two mutually perpendicular axes, wherein the magnetic pole position inferring means infers the position of the magnetic pole by using a value of the current or the voltage detected with timing of a predetermined phase with respect to the AC current signal for inference use or the AC voltage signal for inference use. In addition, the object of the present invention can also be achieved by detecting the current or the voltage for each half period of the AC current signal for inference use or the AC voltage signal for inference use and inferring the position of the magnetic pole from the quantity of changes in the detected value.
Also, in order to achieve the object of the present invention described above, there is further provided another motor control apparatus having a magnetic pole position inferring means for inferring the position of a magnetic pole of a synchronous motor by applying an AC current signal for inference use or an AC voltage signal for inference use in the direction of one of two mutually perpendicular axes of an orthogonal axis coordinate system and detecting a current or a voltage in the direction of the other of the two mutually perpendicular axes, wherein the magnetic pole position inferring means corrects a set value of the position of the magnetic pole in accordance with a result of the multiplication of the current or the voltage in the direction of the other of the two mutually perpendicular axes by a predetermined gain. On top of that, the object of the present invention can also be achieved by correcting a set value of the position of the magnetic pole in accordance with a result of carrying out proportional and integral or proportional, integral and differential processing on the current or the voltage in the direction of the other of the two mutually perpendicular axes.
REFERENCES:
patent: 4006977 (1977-02-01), Harrow et al.
patent: 6005365 (1999-12-01), Kaneko et al.
patent: 7-245981 (1995-09-01), None
Kaneko Satoru
Masaki Ryozo
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Hitachi , Ltd.
Masih Karen
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