Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-02-22
2001-12-11
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S156070, C310S156390, C310S156570, C310S261100, C310S162000
Reexamination Certificate
active
06329734
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a permanent magnet and reluctance type rotating machine.
2. Description of the Related Art
FIG. 1
shows the schematic structure of a permanent magnet and reluctance type rotating machine (not prior art).
In
FIG. 1
, the permanent magnet and reluctance type rotating machine
101
comprises a stator
103
carried by a housing or the like and a rotor
105
rotatably arranged in the stator
103
. The stator
103
consists of a stator core
107
and armature windings
109
wound around the stator core
107
. In the rotor
105
, four pairs of permanent magnets
113
are arranged crosswise in a rotor core
111
. Magnetic poles
115
are defined by respective core portions in which the magnetic permanents
113
are arranged, while interpoles
119
are constituted by non-magnetic portions
117
between the permanent magnets
113
.
FIG. 2
shows magnetic flux &phgr; d due to the armature current, flowing along the directions of respective pole axes of the rotor core
111
. In this state, since the magnetic paths are constituted by the core portion forming the poles
115
, the flux is easy to flow because of an extremely small magnetic reluctance.
FIG. 3
shows another magnetic flux &phgr; e due to the armature current, flowing along the directions of respective radial axes passing through respective circumferential centers of the interpoles
119
. Although the magnetic flux &phgr; e of the interpoles
119
does build the magnetic paths crossing the permanent magnets
113
interposing the interpoles
119
, the flux due to the armature current is decreased under the high reluctance action of the permanent magnets
113
because of their relative permeability of approx.
1
.
The permanent magnets
113
on both sides of each interpole
119
are magnetized in the directions substantially perpendicular to the pole axes. Therefore, as shown in
FIG. 4
, the flux generated from each permanent magnet
113
partially circulates in the following order: one pole of the permanent magnet
113
, a magnetic portion
121
in the vicinity of the periphery of the core
111
, the pole
115
and the opposite pole of the magnet
113
, thereby to form a magnetic circuit &phgr; ma. Further, a part of flux from each permanent magnet
6
also flows into the stator
107
through the gap between the rotor
105
and the stator
107
and subsequently passes through the pole
115
of the rotor
105
, the neighboring permanent magnet
6
and the originating permanent magnet
113
in order, thereby to form another magnetic circuit &phgr; mb.
Returning to
FIG. 3
, the interlinkage flux of the permanent magnets
113
distributes in the opposite direction to the magnetic flux &phgr; e (by the armature current) flowing along the center axes of the interpoles
119
to repel the magnetic flux &phgr; e into their mutual negation. At the gap in the vicinity of each interpole
119
, there is a reduction in gap flux density derived from the armature current due to the flux of the permanent magnets
113
. Consequently, there is produced a great change in the gap flux density between the vicinity of each pole and that of each interpole. In other words, the change of gap flux density with respect to the rotational position of the rotor
105
becomes so large that the change of magnetic energy is increased. Further, under the loaded situation, the rotor
105
is subjected to great magnetic saturation by load currents owing to the presence of the magnetic portions
121
each forming a magnetic short circuit on the boundary between the pole
115
and the interpole
119
. The magnetic flux of the magnets
113
distributed in the interpoles
119
is increased. Consequently, there is produced a great unevenness in the distribution of gap flux density by both magnetic reluctance and flux of the permanent magnets
113
and therefore, the magnetic energy is remarkably changed to produce a great output.
Next, we describe the adjusting range of terminal voltage in order to accomplish the operation of the rotating machine at a wide range of variable speeds. Since the permanent magnets
113
exist in only a part of each interpole
119
, the rotating machine has a narrow surface area of the permanent magnets
113
in comparison with that of the general rotating machine where the permanent magnets are arranged in the whole circumference of the rotor, also exhibiting a small interlinkage flux due to the permanent magnets
113
.
Furthermore, under condition that the machine is unexcited, a considerable quantity of the permanent magnets' flux flows the magnetic portions
121
to become the leakage flux in the rotor core
111
. Accordingly, since it is possible to reduce an induced voltage remarkably in this condition, the core loss at the machine's unexciting is reduced. Additionally, when the windings
109
malfunction in a short circuit, the over-current is reduced.
When the rotating machine is loaded, the terminal voltage is induced owing to the addition of interlinkage flux by the armature current (i.e. both exciting current and torque current of the reluctance rotating machine) into the interlinkage flux by the permanent magnets
113
.
In the general permanent magnet type rotating machine, it is impossible to adjust the terminal voltage since a great deal of terminal voltage is occupied with the interlinkage flux of the permanent magnets
113
. While, in the permanent magnet-reluctance type rotating machine
101
, it is possible to adjust the terminal voltage in a wide range by controlling the component of exciting current because of small interlinkage flux of the permanent magnets
113
. In other words, as the component of exciting current can be adjusted so as to attain the terminal voltage less than a voltage of the power source voltage corresponding to the velocity, the rotating machine is capable of driving at a wide range of variable speeds (from its base speed) to by a constant voltage.
Furthermore, as the voltage is not restricted by field-weakening under the forced control, there is no possibility of the occurrence of over-voltage even if the control is not effected at the time of the machine's rotating at high speed.
Additionally, since a part of flux from each permanent magnet
113
, that is, flux &phgr; ma leaks out into the short circuit of the magnetic portion
121
, it is possible to reduce the diamagnetic field in the permanent magnets
113
. Thus, since the permanent magnet's operational point is raised on its demagnetizing curve representing the B(magnetic flux density)—H(field intensity) characteristics, that is, the permeance coefficient becomes large, the demagnetizing-proof characteristics against temperature and armature reaction is progressed. Additionally, as the permanent magnets
113
are embedded in the rotor core
111
, it will be expected that the rotating machine has a merit to prevent the permanent magnets
113
from scattering due to the rotation of the rotor
105
.
On the contrary, since respective core portions around holes
123
for the permanent magnets
113
, especially, radial outside portions of the interpoles
119
are formed as thin as possible in view of reducing the flux leakage from the magnets
113
, it is unexpectedly difficult to cope with centrifugal force of the permanent magnets
113
in the above-mentioned rotating machine. Particularly, in case of the application for a high-speed rotating machine, there may be caused various problems of the scattering of the permanent magnets
113
, the breakage of the rotor
105
, etc.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a permanent magnet-reluctance type rotating machine which is capable of high-speed rotation and high cooling performance against the rotor core and which can improve the reliability of machine while avoiding both high load and temperature demagnetizing action of the permanent magnets.
According to the first aspect of the invention, the object of the present invention described above
Arata Masanori
Hashiba Yutaka
Sakai Kazuto
Takahashi Norio
Tsutsui Hirotsugu
Kabushiki Kaisha Toshiba
Mullins Burton S.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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