Self-excited reluctance motor

Details Self-excited reluctance motor Self-excited reluctance motor

2000-12-07

2002-11-12

Ro, Bentsu (Department: 2837)

Electricity: motive power systems

Limitation of motor load, current, torque or force

C318S254100, C318S701000

Reexamination Certificate

active

06479959

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a Switched Reluctance Motor (SRM), and more particularly to a self-excited reluctance motor capable of generating a rotating force with a simple commutator made based on a classical commutation theory, without using a commutation logic of an electric circuit, or making any changes to characteristics of a conventional SRM.
2. Description of the Related Art
Generally, a Switched Reluctance Motor (SRM) rotates at a relatively higher speed with a simpler structure, when compared to an induction motor. Also, by using a semiconductor element as a switch for controlling electric power, the SRM not only has an accurate control on various functions are possible, but also has a higher efficiency. For such advantages of the SRM, there have been many researches and developments of SRM.
As shown in
FIG. 1
, the SRM simply includes a stator
1
and a rotator
3
without a commutator. The SRM has a dual-pole structure which has stator poles
2
and rotator poles
4
. The rotator
3
is formed of silicon steel plates which are stacked on each other firmly. In the stator
1
, two opposing stator poles
2
are connected by a wire in parallel or series in order to generate a magnetic flux toward the same direction.
The SRM mainly includes a 6/4 pole SRM having six stator poles and four rotator poles, a 12/8 pole SRM having twelve stator poles and eight rotator poles, and 24/16 pole SRM having twenty-four stator poles and sixteen rotator poles.
Among these, a driving principle and method of the SRM will be described, with reference to an example of 3-phase 12/8 pole SRM.
First, the driving principle of the SRM will be described with reference to
FIGS. 1 and 2
.
FIG. 1
is a sectional view of a conventional 3-phase 12/8 pole SRM. Although
FIG. 1
shows only certain stator poles
2
being wound by coils for a more convenient explanation thereof, it will be fully understood by those skilled in art that the other stator poles
2
are also wound by phase-A, phase-B, and phase-C coils in the same manner.
When electric voltage is applied to a wire (a-a′) winding the stator poles
2
a
and
2
a
′, the stator poles
2
a
and
2
a
′ are excited, and the neighboring rotator poles
4
are rotated in the direction of arrow of
FIG. 1
, to be aligned with the stator poles
2
a
and
2
a
′ which are excited. Before the alignment of the excited stator poles
2
a
and
2
a
′ and the neighboring rotator poles
4
, the electric voltage supply to the wire (a-a′) is cut off. Next, electric voltage is supplied to the neighboring stator wire (b-b′), and the stator poles
2
b
and
2
b
′ are excited. Accordingly, in the same manner as described above, the neighboring rotator poles
4
of the newly excited stator poles
2
b
and
2
b
′ are rotated in the direction of arrow of
FIG. 1
to be aligned with the newly excited stator poles
2
b
and
2
b
′. As the stator poles
2
a
and
2
a
′,
2
b
and
2
b
′, and
2
c
and
2
c
′ are sequentially excited in the above-described manner, the rotator
3
is continuously rotated.
FIGS.
2
(
a
) to
2
(
b
) are sectional views for showing the positions of the rotator poles
4
with respect to excited stator poles
2
of the 12/8 pole SRM. As shown in FIG.
2
(
a
), when the rotator poles
4
b
are aligned with the excited stator poles
2
a
and
2
a
′ in a straight line (hereinafter called alignment position), a torque is not generated even when electric current flows in the stator wire (a-a′). Meanwhile, as shown in FIGS.
2
(
c
) and
2
(
d
), when the rotator poles
4
b
are out of alignment position with the stator poles
2
a
and
2
a
′, the rotator
3
generates a torque to go to the alignment position.
As shown in FIG.
2
(
b
), when middle points of the neighboring poles
4
a
and
4
b,
and
4
c
and
4
d
of the rotator
3
are aligned with the excited stator poles
2
a
and
2
a
′ in straight lines (Q: non-alignment position), as in the alignment state, a torque is not generated even when electric current flows in the stator wire (a-a′). If the rotator poles
4
are out of the alignment position even by a slight degree, the excited stator poles
2
attract the nearest rotator poles
4
to a new alignment position, generating a torque.
As shown in FIGS.
2
(
c
) and
2
(
d
), when the rotator poles
4
are not in the alignment or non-alignment position, and when electric current flows in the stator wire (a-a′, b-b′, or c-c′) of the stator poles
2
a
and
2
a
′,
2
b
and
2
b
′, or
2
c
and
2
c
′, a torque is generated to align the rotator
3
to the alignment position as in FIG.
2
(
a
).
Next, a driving circuit for driving the 3-phase 12/8 pole SRM will be described. In order to drive the SRM, a driving converter is required. Generally, the driving converter has to i) supply a voltage to a wire of a stator pole
2
which corresponds to a rotator pole
4
, ii) control or maintain the electric current at a suitable level for exciting the stator pole
2
, and iii) supply a backward voltage for electric current extinction at an excited phase. The requirement iii) is mainly conducted by a diode.
Currently, many converter topologies have been studied to control the SRM, in a manner of reducing converter manufacturing cost by reducing a number of switching elements, and also improving a controlling performance.
As a driving converter, there mainly are Asymmetric Bridge Converter, BifillarWinding Converter, Split-Source Converter, Capacitor-Dump converter, Resistor-Dump Converter, and Switch-Shared Converter available at the present time. Among these converters, the driving method of the driving converter will now be described briefly with a reference to an example of the Asymmetric Bridge Converter.
FIG. 3
is a circuit diagram for showing a conventional Asymmetric Bridge Converter, especially for showing an electric circuit for driving the 3-phase 12/8 pole SRM. As shown in
FIG. 3
, the Asymmetric Bridge Converter includes plural pairs of switches (transistor elements T
1
and T
2
, T
3
and T
4
, and T
5
and T
6
) and diodes (D
1
and D
2
, D
3
and D
4
, and D
5
and D
6
).
In the electric circuit, by turning on and thus supplying Direction Current voltage to the pair of switches T
1
and T
2
, or T
3
and T
4
, or T
5
and T
6
connected to phase-A, phase-B, or phase-C, the corresponding stator poles
2
are excited. While electric current flows in the stator wire, the level of electric current is controlled by selectively turning on or off one or both of the pair of switches T
1
or/and T
2
, or T
3
or/and T
4
, or T
5
or/and T
6
. Accordingly, electric current circulates through one diode D
1
or D
2
and one switch T
1
or T
2
, or circulates through both of the diodes D
1
and D
2
, charging a condenser. Next, when the pair of switches T
1
and T
2
are turned off, electric current is dissipated. Here, before an inductance of corresponding phase draws a negative slope, the electric current should be reduced to an dissipation or to a negligible degree.
Since the conventional converter is formed of a plurality of electric elements, the structure thereof is complex, and the manufacturing cost increases. Accordingly, it is almost impossible to employ the converter in a low-price devices. Further, in order to control the switches T
1
and T
2
, T
3
and T
4
, and T
5
and T
6
, a separate controlling means such as a microcomputer is required. Since a control algorithm also should be developed, it is hard to employ the converter to control the SRM.
SUMMARY OF THE INVENTION
The present invention has been made to overcome the above-mentioned problems of the related art, and accordingly, it is an object of the present invention to provide a selfexcited reluctance motor capable of generating a rotating force with a simple commutator and without having to use a high-price electric circuit.
The above object is accomplished by a self-excited

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