Counter rotating nested cylinders in electrical machinery

Details Counter rotating nested cylinders in electrical machinery Counter rotating nested cylinders in electrical machinery

2000-02-18

2001-10-16

Mullins, Burton S. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S114000, C310S154010, C310S156010, C310S266000, C310S152000

Reexamination Certificate

active

06304017

ABSTRACT:

FIELD OF THE INVENTION
This invention relates in general to electric motors or generators, and more specifically to an electric motor or generator utilizing a cylindrical permanent magnet field source.
BACKGROUND OF THE INVENTION
In electrical generators the aim is always to maximize the magnetic flux threading the coils in which the generated current flows because the electromotive force generated is directly proportional to that flux. Three factors determine total flux: (1) flux density, (2) threaded coil area, and (3) number of coils. An extremely useful magnetic generator is described in the inventor's U.S. patent application Ser. No. 09/034,073, entitled “Cylindrical Permanent Magnet Magic Ping Electric Motor and Generator,” which is incorporated herein by reference. That application describes a generator in which a rotating magic cylinder provides a high magnetic field that threads a compact coil in its central cavity causing a large flux through the coil. In that device, the cylinder's rotation causes the flux to alternate because, the angle of the field with respect to the plane of the coil changes linearly with time, and the area of the coil normal to the field varies periodically based on the formula:
A
n
=A
sin &ohgr;
t
  (1)
where A is coil area and A
n
is the area of the coil normal to the field. Based on this relationship, the total flux can vary sinusoidally because magnetic flux:
&PHgr;=
HA
k
=H A
sin &ohgr;
t=&PHgr;
A
sin &ohgr;
t
  (2)
where &PHgr;
A
is flux amplitude. Since the induced electromotive force is proportional to the flux, the electromotive force is also sinusoidal, resulting in an Alternating Current. The field magnitude in that device's coil material is constant (H) and induces lossy eddy currents that are proportional to the square of the field magnitude.
The present invention provides a pair of coaxial nested magnetic cylinders rotated with respect to each other so that each cylinder contributes the same amount of magnetic field to the total, i.e. each contributes H/2. In order to accomplish this, it is necessary for the radius, r
b
, of the border between the inner and outer cylinders, be calculated according to the following formula:
r
b
={square root over (r
i
+L )}
r
o
  (3)
where r
i
is the radius of the core cavity and r
o
is the outer radius of the system. The devices of the present invention generate currents equivalent to the single rotating magnetic cylinder, without the disadvantages, shortcomings and limitations of eddy current losses experienced by single rotating magnetic cylinders.
SUMMARY OF THE INVENTION
The present invention is directed to an electric motor or generator utilizing a counter rotating nested cylindrical permanent magnet composed of a pair of nested magic cylinders, each having a plurality of sections, with each section having a predetermined magnetic orientation or magnetization direction. In this device, each of the two nested magic cylinders contributes the same amount of magnetic field to the total; i.e. each nested magic cylinder contributes H/2, where H is the total field produced.
In accordance with the present invention, when these cylinders are aligned they combine their fields to equal H, the same as that for the undivided single magic ring cylinder described above. When the nested cylinders rotate in opposite directions at the same angular speed, the magnetic field, instead of the threaded normal area, will vary sinusoidally, according to the formula:
&PHgr;=
A
(
H
sin &ohgr;
t
)  (4)
instead of the varying magnetic field of the single rotating magic cylinder, according to the formula:
&PHgr;=
H
(
A
sin &ohgr;
t
)  (5)
The results of these equations are, of course, the same. However, the generation of Eddy currents due to relative motion of field and coil material depends on the magnitude of the magnetic field, which is constant in formula (4) at maximum value, but the magnitude of the magnetic field varies sinusoidally in formula (3) and averages only:
{overscore (H)}=
0.707
H
  (6)
Since losses are proportional to the square of the magnetic field average:
L
2
=0.5
L
3
  (7)
where L
2
and L
3
, respectively, are the losses in the counter rotating and single cylinder embodiments. In
FIGS. 1A and 1B
conceptual nested rotating cylinders
5
and single rotating cylinder
5
′ are compared. In
FIG. 1A
, rotating cylinders
6
and
7
rotate about a coil cavity
8
, with an indicated rotational direction
9
. The small arrows show direction of magnetization and the large arrow shows the magnetic field's direction.
FIG. 1A
shows the relative positions of the rotating cylinders
6
and
7
aligned to produce the maximum strength.
FIG. 1B
depicts a single rotating cylinder
5
′ with a coil cavity
8
′ and a rotational direction
9
′. Additionally, the counter-rotating nested cylinders of the present invention can also be configured to generate electrical beats by an unequal rotational speed for the two counter-rotating cylinders. Where the ratio of beat frequency to fundamental frequency is:
f
i
-
f
a
f
r
(
8
)
and the difference between the two rotational speeds f
i
, f
a
is the beat frequency and f
f
is the average of f
I
and f
a
.
The crucial idea behind all the counter-rotating nested cylinder structures of the present invention is that the magnetic materials are rigid i.e., they keep their magnetization in each other's presence and in the presence of the field they themselves generate. Therefore, the magnetic field that each component produces at any point can be added vectorially to those produced by the other components to obtain the total. If current is sent through the coils the cylinders can be made to rotate in opposite directions forming a motor.
The nested magic cylinders are rotatable and coaxially arranged so that the bore of the inner cylinder provides a central working space. The predetermined magnetic orientation of each cylinder's sections is arranged to create a relatively strong and uniform magnetic field within the central working space or bore in which copper wires are imbedded to form a core. A core having copper wires embedded within the working space is coaxially positioned within the bore to act as a rotor and when current flows within the copper wires an electric motor is therefore formed. Alternatively, a rotating device can mechanically rotate the rotor or core, inducing a current in the copper wires in the rotor or core thereby forming an electric generator. The sections of the nested permanent magnet cylinders are arranged such that each of the sections have a magnetic orientation forming a pair of coaxial “magic” cylinders or rings that counter rotate with respect to each other. This results in a relatively large magnetic field within the inner cylinder's central working space with minimal magnetic flux leakage exterior to the central working space. In a preferred embodiment the pair of magnetic cylinders counter rotate and the core remains stationary, which simplifies the required electrical connections with the core.
Accordingly, it is one object of the present invention to provide a compact efficient motor or generator that is relatively easily manufactured.
It is an advantage of the present invention that magnetic flux leakage due to eddy currents is substantially reduced or eliminated.
It is a feature of the present invention that a pair of rotatable nested permanent magnet cylinders, with each cylinder having a plurality of sections with different radial magnetic orientations is used, produces a relatively strong magnetic field within a central working space.
These and other objects, advantages, and features will become readily apparent in view of the following detailed description.


REFERENCES:
patent: 5783893 (1998-07-01), Dade et al.
patent: 6049152 (2000-04-01), Nakano
patent: 6054789 (2000-04-01), Leupold
Leupold, H.A., “Rare-Earth Permanent Magnets”, edi

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