Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-29
2001-05-29
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S187000, C310S256000, C310S162000, C310S012060
Reexamination Certificate
active
06239530
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a new reluctance electric machine and, more particularly, to a rotating or linear sub synchronous reluctance machine. As is known by those of skill in the art, one of the best known and most employed types of reluctance electrical machines is the switched reluctance motor, which presents, as a limiting aspect to the use thereof, the existence of torque and speed oscillations, as well as the difficulty of imposing high variation rates in the electric current. Other drawbacks of this switched reluctance motor relates to the fact that the circuits employed for controlling and feeding them are very complex and expensive, specially in respect of high-power machines.
2. Description of the Prior Art
As an alternative to solve the above mentioned drawbacks, the patent Brazilian application PI9400880-9, published on Dec. 24, 1995 and relating to “Reluctance electrical machine” has been proposed, which provided an electrical machine comprised of a rotor and a stator. Said stator was provided with a core comprised of magnetic plates and provided with longitudinal teeth projecting towards the rotor. Said stator also comprised a plurality of grooves capable of receiving a multi-phase winding, said winding being comprised of a plurality of coils homogeneously surrounding the stator's magnetic material. As a supplementation, said rotor was formed by a core of magnetic plates provided with longitudinal teeth projecting towards the stator. Thus, upon energizing of said coils by a balanced multiphase voltage, a rotating field was generated, which caused a relative movement between rotor and stator.
However, and even though such machine was capable of overcoming the drawbacks of the prior art, there is still the fact that the electrical machine described on in Brazilian patent application PI 9400880-9 has the particular drawback of a low power factor, and in some cases may increase the cost of the drive system.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a reluctance electrical machine providing high torque at low speeds, advantageously replacing the switched reluctance, conventional electrical machines.
It is an object of the present invention to provide a reluctance electrical machine presenting high torques at low speeds, advantageously replacing in terms of cost and maintenance the conventional mechanical reduction machines that multiply the torque and decrease the speed.
It is an object of the present invention to provide a reluctance electrical machine that allows a large control of the rotation and torque thereof, without the need of a complex and expensive power and control circuit.
Another object of the present invention is to provide a reluctance electrical machine that, by reason of its constructive features, does not present oscillations in the resulting torque and speed.
Another object of the present invention is to provide an improvement on the reluctance electrical machine as per the above described Brazilian patent application PI 9400880-9, having characteristics of a high power factor.
These and other objects and advantages of the present invention are achieved by a sub-synchronous reluctance electrical machine comprised of a stator provided with a core composed of magnetically uncoupled or weakly coupled sectors of ferromagnetic plates having longitudinal teeth arranged on the face thereof facing the rotor and provided with grooves to house a winding, the latter being comprised of a plurality of coils surrounding the ferromagnetic material, thereby creating a magnetic field when the winding thus defined is energized.
Said rotor is an integral part of the machine and is in turn provided with a core comprised of ferromagnetic plates having longitudinal teeth arranged uniformly along its face turned towards the stator. In addition, the number of teeth on the rotor is necessarily different from the number of teeth on the stator.
The machine is further provided with a device for monitoring and identifying the relative position between the stator and rotor teeth in order to allow the identification of the region of largest magnetic permeability between the rotor and the stator, in order to allow the proper feeding of the stator coils, thereby obtaining the maximum possible torque.
The present invention has constructive characteristics similar to those of the machine described in Brazilian patent application PI9400880-9, however it is fundamentally different therefrom in the following items:
The stator core is comprised of magnetically uncoupled or weakly coupled sectors, contrary to the machine described on the Brazilian patent application PI9400880-9, which employs integral magnetic plates; and
The coils are individually fed with currents controlled and monitored by devices identifying the relative position between the stator and rotor teeth, whereas in the Brazilian patent application PI9400880-9 the coils are multiphase and are energized by balanced multiphase voltages.
These differences allow the machine subject matter of the present invention to possess a high power factor, which means that during the operation thereof the machine absorbs low currents.
Accordingly, it is an object of the present invention to provide a sub-synchronous reluctance electrical machine of the type comprising at least one rotor formed of ferromagnetic plates and provided with a plurality of uniformly distributed teeth and at least a stator provided on the surface thereof facing said rotor with a second plurality of teeth, also uniformly arranged, plus windings, said windings being selectively fed by a current power source, and the at least one stator is formed by a series of magnetically uncoupled or weakly coupled sectors of ferromagnetic plates, each sector comprising at least one winding, the at least one winding of each sector having the power thereof controlled by a monitoring device, and the number of teeth on the stator being different from the number of teeth on the rotor.
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patent: 4475051 (1984-10-01), Chai et al.
patent: 4713570 (1987-12-01), Mastromattei
patent: 4733117 (1988-03-01), Perrins
patent: 4990809 (1991-02-01), Artus et al.
patent: 5173651 (1992-12-01), Buckley et al.
patent: 5283486 (1994-02-01), Kobori
patent: 6025668 (2000-02-01), Kolomeitsey
patent: 6051898 (2000-04-01), Sakamoto
Dinh Le Dang
Elevadores Atlas-Schindler S/A
Hochberg D. Peter
Holt William H.
Ramirez Nestor
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