Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2001-04-05
2003-07-01
Dang, Khanh (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S701000
Reexamination Certificate
active
06586897
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a switched reluctance motor (hereinafter, referred to as “SRM”), and more particularly, a method of controlling alignment of a rotor of an SRM with respect to a stator and an SRM driving circuit for realizing the same in which current flowing into phase coils surrounding each stator salient pole pair in respective motor phases of a stator of the SRM is detected upon the starting of the SRM to compare the magnitude values of the detected current with each other so that the alignment of a rotor with respect to the stator is controlled in such a fashion that rotor salient pole pair of the rotor is brought into alignment with a corresponding stator salient pole pair of a specific motor phase with a phase coil into which current of the lowest level flows, thereby shortening the starting time of the SRM and reducing a noise generated upon the initial alignment of the rotor with respect to the stator.
2. Description of the Related Art
A synchronous motor is a type of an alternating current (AC) motor, in which a change of an excitation state of the motor allows for adjustment of its power-factor, and which rotates at a synchronous speed despite a variation of a load.
The SRM has the same characteristics as that of such a synchronous motor, but refers to a motor which does not have a direct current (DC) excitation state and operates synchronously by a reluctance torque produced by an unbalanced distribution of a magnetic reluctance due to the relative position between the stator salient pole pairs of the stator and the rotor salient pole pairs of the rotor.
FIG. 1
is a cross-sectional view illustrating an example of a typical three-phase SRM.
Referring to
FIG. 1
, there is shown a three-phase SRM
100
including a stator having a plurality of radially inwardly extending stator poles
101
p
configured as diametrically opposed stator salient magnetic pole pairs A—A, B—B, C—C around each which a phase coil (i.e., the windings around any two diametrically opposed stator salient poles connected in series or in parallel to define a motor phase)
101
c
is wound, and a rotor
102
disposed about a shaft within the stator
101
and having a plurality of radially outwardly extending rotor poles
102
p
configured as diametrically opposed rotor salient pole pairs for rotating by a reluctance torque produced by an unbalanced distribution of a magnetic reluctance due to the relative position between the stator salient pole pairs
101
p
of the stator
101
and the rotor salient pole pairs
102
p
of the rotor
102
.
The driving of the SRM
100
having such a configuration requires detection of the position of the rotor
102
. At least one sensor is generally used to detect the position of the rotor
102
. In the case of a single sensor three-phase SRM using one sensor for detecting the position of the rotor
102
, a pair of rotor salient pole
102
p
of the rotor
102
must be aligned previously with a pair of corresponding stator salient pole
101
p
, i.e., A—A, B—B, or C—C of the stator
101
in a predetermined motor phase for the initial starting of the SRM
100
. However, in such a three-phase SRM
100
, when the pair of rotor salient pole
102
p
is brought into misalignment with the pair of corresponding stator salient pole A—A, B—B, or C—C in the predetermined motor phase, it cannot be moved toward the precise alignment position with the corresponding stator salient pole pair A—A, B—B, or C—C. In order to resolve the above misalignment problem, as shown in
FIG. 2
, the prior art has adopted a method in which the nearest rotor salient pole pair
102
p
is aligned sequentially with each corresponding stator salient pole pair
101
p
in each motor phase in the order of phase A→phase B→phase C in three motor phases (i.e., phase A, phase B and phase C) to bring the nearest rotor salient pole pair
102
p
into alignment with the corresponding stator salient pole pair
101
p
in a desired phase among three motor phases A, B and C while avoiding the misalignment, and a method in which the nearest rotor salient pole pair
102
p
is aligned sequentially with each corresponding stator salient pole pair
101
p
in each motor phase in the order of phase A→phase B in three motor phases A, B and C to bring the nearest rotor salient pole pair
102
p
into alignment with the corresponding stator salient pole pair
101
p
in a desired phase among three motor phases A, B and C while avoiding the misalignment. At this time, a voltage pulse is applied to the phase coil surrounding the corresponding stator salient pole pair
101
p
in the desired phase so that the nearest rotor salient pole pair
102
p
is brought into alignment with the corresponding stator salient pole pair
101
p
. That is, as shown in
FIG. 2
, the voltage pulse having a constant width is first applied to the phase coil surrounding the corresponding stator salient pole pair
101
p
at a relatively long interval. Then, after applying the voltage pulse several times, the interval of the voltage pulse is reduced gradually and the voltage pulse is applied continuously until its interval is reduced to a desired interval to bring the nearest rotor salient pole pair
102
p
into alignment with the corresponding stator salient pole pair
101
p
around which the energized phase coil is wound in a desired phase.
However, in the above conventional rotor alignment method, after the nearest rotor salient pole pair
102
p
is first aligned with a corresponding stator salient pole pair
101
p
for a desired phase among three motor phases A, B and C, the nearest rotor salient pole pair
102
p
is aligned with a corresponding stator salient pole pair
101
p
around which an energized phase coil is wound for the next phase. At this time, in alignment of each rotor salient pole pair of the rotor
102
of the SRM
100
, the farther a rotor salient pole pair
102
p
of the rotor
102
is from a corresponding stator salient pole pair
101
p
for alignment, the more current become to flow into the phase coil (the windings)
101
c
surrounding the corresponding stator salient pole pair
101
p
. Moreover, such large amount of current generates a high noise when bringing each rotor salient pole pair
102
p
of the rotor
102
into alignment with each corresponding stator salient pole pair
101
p
of the stator
101
. Further, as described above, the nearest rotor salient pole pair is aligned sequentially with each corresponding stator salient pole pair in each corresponding motor phase in three phases or two phases alignment manner in order to avoid the misalignment of the rotor, thereby lengthening the starting time of the motor.
SUMMARY OF THE INVENTION
Therefore, the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a method of controlling alignment of a rotor of an SRM and an SRM driving circuit for realizing the same which shortens the starting time of the SRM and reduces a noise generated upon the initial alignment of each rotor salient pole pair of the rotor with respect to each corresponding stator salient pole pair of the stator.
According to one aspect of the present invention, there is provided a method of controlling alignment of a rotor of an SRM with respect to a stator, the SRM including a stator having a plurality of diametrically opposed stator salient magnetic pole pairs around each which each of a plurality of phase coils is wound, and a rotor disposed about a shaft within the stator and having a plurality of diametrically opposed rotor salient pole pairs, comprising the steps of:
(a) applying a voltage pulse having an identical magnitude to each phase coil surrounding the plurality of pairs of stator salient magnetic poles in a plurality of respective motor phases of a stator of the SRM upon the initial starting of the SRM;
(b) detecting current flowing into the each phase coil in the plurality of respective motor phases, respectively, in accordance to the applica
Kim Sang-Young
Lim Jun-Young
Birch & Stewart Kolasch & Birch, LLP
Dang Khanh
LG Electronics Inc.
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