Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-08-10
2004-03-02
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S001000, C310S191000
Reexamination Certificate
active
06700242
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetic flux control means for a permanent-magnet motor-generator that is comprised of a rotor of permanent-magnet pieces supported for rotation in a stator housing, and a stator surrounding around an outside periphery of the rotor.
2. Description of the Prior Art
Modern advanced permanent magnets of high performance have become much employed on a rotor of a motor-generator. Moreover, as the motor-generator having the rotor structure of permanent magnets is high in efficiency of electromechanical energy conversion and simple in construction, its use has recently grown in industrial machines and instruments of various kinds. Then, much research and development have continued to make the motor-generator compact or slim in construction, with even high performance and high power output, and correspondingly necessitated a growing variety of parts and components. In order to increase a torque at low speed in operation of the conventional motor-generators, it is effective to increase the strength of the magnetic field of the stator around the rotor, thereby raising the torque. With the motor-generators, thus, increasing well the torque causes the increase of electromotive force at a low speed, contributing to the provision of commercially viable power source for machines.
Among the conventional a-c motor-generators capable of developing high-power output, there is a motor-generator disclosed in Japanese Patent Laid-Open No. 236260/1995, which is co-pending application of the present inventor. The prior motor-generator controls magnetic flux density in proportion to the speed in revolutions per minute (rpm) of the rotor to adjust properly an amount of the generated amperes or voltages. To cope with this, a control ring is arranged between the rotor and the stator for rotation relatively of them and further a magnetic flux permeable member is provided in the control ring.
Further disclosed in Japanese Patent Laid-Open No. 261988/2000, which is also co-pending application of the present inventor, is a motor-generator in which a cylindrical controller member is arranged on the inside surface of the stator, the cylindrical controller member being formed of magnetic permeable pieces and non-permeable pieces, which alternate in position circularly in the form of a cylinder. The cylindrical controller member is moved selectively to any angular position relatively to the stator in accordance with an operating phase of the motor-generator. That is to say, to get it started, the cylindrical controller member is moved to an angular position where the magnetic flux permeable pieces of the controller member are brought into radial alignment with the teeth of the stator, each to each tooth. In contrast, when the rotor comes to rest, the cylindrical controller member is moved to another angular position where the magnetic flux permeable pieces may be cooperative with the teeth of the stator core to provide the magnetic path around the overall circumference of the controller member, thus allowing the magnetic flux to pass circumferentially of the controller member with a uniform distribution, thereby ensuring smooth rotation of the rotor.
In conventional motor-generators, there is a way in which the on-off switch operation of a power transistor chops the generated power to produce a chopped voltage. However, this way has a major problem of causing a high ripple voltage, which makes it tough to control the generated power. With the prior motor-generator disclosed in the senior application stated earlier, there is provided an annular member composed of magnetic flux permeable pieces arranged circularly at a pitch equal to a stator tooth pitch, with resinous pieces being each interposed between any adjoining magnetic flux permeable pieces so as to match the stator slots. The annular member is installed around the rotor for angular movement relatively to the stator. At low speed in rpm the annular member is moved to an angular position where the magnetic flux permeable pieces come in radial alignment with the stator teeth. In contrast, when the rotor is driven at a high speed, the annular member is shifted to another angular position where the magnetic flux permeable pieces are each displaced out of the alignment with the associated stator tooth to reduce an area allowing the magnetic flux to pass through there. With the construction in which the magnetic flux permeable pieces are arranged intermittently and jointed together with resinous pieces to form a cylinder, the resinous pieces are much subjected to wear during revolution of the rotor. Moreover, the annular member, since being subject to restoring force, experiences a large force rendering magnetism much more when the magnetic path is reduced. This makes a troublesome problem of causing deformation of the annular member, which might lead to breakage of the annular member.
In conventional motor-generators, there is a way in which the on-off switch operation of a power transistor chops the generated power to produce a chopped voltage. However, this way has a major problem of causing a high ripple voltage, which makes it tough to control the generated power. With the prior motor-generator disclosed in the senior application stated earlier, there is provided an annular member composed of permeable pieces arranged circularly at a pitch equal to a stator tooth pitch, with resinous pieces being each interposed between any adjoining permeable pieces so as to match the stator slots. The annular member is installed around the rotor for angular movement relatively to the stator. At low speed in rpm the annular member is moved to an angular position where the permeable pieces come in radial alignment with the stator teeth. In contrast, when the rotor is driven at a high speed, the annular member is shifted to another angular position where the permeable pieces are each displaced out of the alignment with the associated stator tooth to reduce an area allowing the magnetic flux to pass through there. With the construction in which the permeable pieces are arranged intermittently and jointed together with resinous pieces to form a cylinder, the resinous pieces are much subjected to wear during revolution of the rotor. Moreover, the annular member, since being subject to restoring force, experiences a large force rendering magnetism much more when the magnetic path is reduced. This makes a troublesome problem of causing deformation of the annular member, which might lead to breakage of the annular member.
The permanent-magnet generators need exploiting the greatest possible magnetic force inherent to the permanent magnets while reducing the magnetic force as the speed in rpm of the rotor increases. To cope with this, it is conceivable to provide a generator in which more than one winding is wound in phase on the stator core in a manner to increase the voltage as the rpm rises. According to the generator constructed as stated just above, the production of a desired constant voltage will be realized easily by a way of controlling the magnetic flux passing through the stator in light of an electric current induced in the windings.
The output (U) of the permanent-magnet motor-generator is determined, depending on the magnitude of magnetic force of the permanent magnet, the number of loops or turns of the stator windings and the speed in rpm of the rotor, and is given mathematically by
U
=3
1/2
·(2
&pgr;f
/2
1/2
)·&phgr;
w
1
·kw
1
where f is the frequency, &phgr; is the magnetic flux density, w
1
the number of turns and kw
1
a factor. Here the magnetic flux density is determined in terms of the relation between the magnetic force and magnetic resistance of the permanent magnet, and written in
&phgr;=Ni/Rm, where Ni is the magnetomotive force and Rm is the magnetic resistance.
The magnetic resistance is equal to the magnetomotive force divided by the magnetic flux, or
Rm=L
1
/(&mgr;·S
1
), where L
1
is a distance, S
1
is an area and &mgr; is any relative pe
Browdy and Neimark , P.L.L.C.
Nguyen Tran
LandOfFree
Magnetic flux controls for permanent-magnet motor-generator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Magnetic flux controls for permanent-magnet motor-generator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magnetic flux controls for permanent-magnet motor-generator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3285147