Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2002-04-01
2004-02-10
Patel, Rajnikant B. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S273000, C363S089000, C363S086000
Reexamination Certificate
active
06690145
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed generally to a light weight alternator, and in particular, a permanent magnet-type alternator including a voltage regulator for regulating the voltage output of the permanent magnet-type alternator.
2. Field of the Related Art
Various alternators use wound stator and rotor assemblies in which an electromagnetic force is produced in and around the rotor windings by admitting current through the rotor windings. In such designs, as the magnetic field produced in the spinning rotor couples with the windings at the stator, current is induced in the stator windings. These alternators, however, require brushes or slip rings to maintain a closed circuit for admitting the current necessary in the rotor during rotation. Because the brushes or slip rings are mechanical connections, they are susceptible to wear and corrosion.
The use of permanent magnet alternators have been found to be advantageous since they do not require that current be supplied to the rotor. In other words, the field inherent to and produced by the magnetic material of the permanent magnet alternators induces current in the stator as the magnet poles move in respect to the stator windings. Because it is not required to supply current to the rotor, slip rings and brushes are not required.
While the use of permanent magnet alternators have proven successful for various applications, the prior art systems have several shortcomings. Generally, because the alternator generates excessive heat, internal fans are provided on the drive end to cool the windings and the rotor. This increases the weight of the alternator, and thus, makes it undesirable for use in an automotive or aerospace capacity where fuel efficiency is needed. Moreover, many systems require the attachment of individual magnets to the outer circumferential surface of the rotor, which may result in the failure of the alternator if by chance one or more magnets becomes detached from the rotor due to the high centrifugal forces that result from the rotation of the rotor at high rpm or faulty adhesion between the magnet and surface. Yet another problem associated with permanent magnet alternators is the difficulty associated with controlling the output voltage generated in the stator windings as will otherwise inherently occur when the alternator is driven at variable rotational velocities. These drawbacks of the prior art are especially problematic in the vehicular environment where low cost, high reliability and light weight are all important to achieving a commercially acceptable design.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to overcome the disadvantages in the related art by providing a permanent magnet alternator for use in an automotive or aerospace capacity that is of a size that allows it to be placed in small areas of an automobile or aircraft engine compartment.
It is another object of the present invention to provide a permanent magnet alternator that is light-weight and highly efficient.
It is a yet another object of the present invention to provide a permanent magnet alternator that has a high cooling capacity.
It is still another object of the invention to provide a permanent magnet alternator that allows the rotation of the rotor at high rpm without resulting in the detachment of magnets from the rotor.
It is yet a further object of the invention to provide a permanent magnet alternator with a voltage regulator that independently regulates and controls the charging current produced by the alternator.
These as well as other objects are achieved in accordance with the invention including a permanent magnet alternator assembly provided with a stationary stator, a rotor mounted for rotation within the stator, a winding circuit for generating a magnetic flux, a plurality of permanent magnets for attachment to the rotor, and a retaining shield positioned between the rotor and stator for reducing the effects of centrifugal motion of the rotor during operation of the alternator.
The stator includes a substantially cylindrical core or body in which a plurality of stator poles project radially inward from the stator body. Each stator pole is composed of a longitudinal shank portion including a base end which is attached to the stator body and a distal end which is flared to facilitate ease during assembly of the winding circuit.
The rotor has a substantially cylindrical body having a laminated structure including a core section preferably comprising a non-ferromagnetic material that is both light-weight and non-corrosive such as aluminum, and an outer circumferential surface preferably comprising a ferromagnetic material such as steel or the like. The permanent magnets are fixedly mounted or attached to the outer circumferential surface of the rotor body in alternating polarity. In order to further reduce the overall weight of the alternator, it is preferred that light-weight, yet high field permanent magnets are used, such as those composed of Neodymium-Iron-Boron (NdFeB).
The retaining shield is positioned between the stator poles and the permanent magnets to reduce the effects of centrifugal motion of the rotor body during operation of the alternator, and the undesirable effects of vibration. The retaining shield is preferably a cylindrical sleeve composed of a non-ferromagnetic material such as stainless steel. The use of the retaining sleeve is advantageous in that it reduces the centrifugal forces and allows rotation of the rotor at high rpm without resulting in the detachment of magnets from the rotor and the possible destruction of the alternator.
In a second embodiment, the permanent magnet alternator assembly includes a laminated, bifurcated rotor having a first rotor section and a second rotor section, each rotor section having a substantially cylindrical body composed of a light-weight, non-ferromagnetic material such as aluminum, and an outer circumferential surface composed of a ferromagnetic material such as steel.
A plurality of fan-like projections are provided equidistant on the peripheral surface of each rotor section. The placement of the fans directly on the surface of each rotor section is advantageous since it obviates the need for drive end fans for cooling the rotors and windings, and thus, further reduces the overall weight of the alternator. The fan-like projections project outward from the side of each rotor section in order to provide the efficient distribution of air inside the alternator housing. In particular, the projections project along a plane that lies substantially parallel relative to the outer circumferential surface. In this way, high ambient temperatures produced inside the alternator during rotation of the rotor are significantly reduced.
A third embodiment of the invention includes a permanent magnet alternator having a stator including a substantially cylindrical body and a plurality of spaced stator poles that project outward from a side surface of the stator body. In particular, the stator poles project along a plane lying substantially parallel relative to an outer circumferential surface of said stator body.
A rotor is also provided including a substantially cylindrical body mounted for rotation relative to the stator body in a face-to-face spatial relationship, as opposed to the conventional manner of rotating inside or outside of the stator. Moreover, a plurality of permanent magnets are fixedly mounted equidistant on the rotor body in alternating polarity and project outward from a side surface of the rotor body. In particular, each permanent magnet projects along a plane lying substantially parallel relative to an outer circumferential surface of the rotor. In this way, the rotor body may be operatively positioned relative to the stator body such that the permanent magnets are rotatably aligned in a face-to-face manner with the stator poles so as to generate a continuous alternating flux density magnetic field along a primary flux path.
The winding of the conductors
Edmundson William C.
Murray Ronald E.
Stevens Julius J.
Young Craig G.
Brackett, Jr. Tim L.
E-Tec Corporation
Nixon & Peabody LLP
Patel Rajnikant B.
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