BACKGROUND OF THE INVENTION Field of the Invention:
The present invention relates to a high performance inducting motor and a rotor used therein, especially to a high performace induction motor with rotor having plurality of slots in a shaft direction. Description of Related Art:
Techniques in which an aperture part at each slots is provided at the surface zone of a rotor cone, are disclosed in JP-A-B6060/19B1, JP-A-145753/1981. JP-A-35665/1981, JP-A-207848/1983, and JP-A-28556/1982.
In JP-A-86060/1981 and JP-A-145753/1981, although a rotor is produced by a die-casting method with conductive material, the above—mentioned rotor has such a structure that there is not the conductive material in each slot aperture provided to reduce a leakage of magnetic flux. In JP-A-35665/1981, it is disclosed that a size of each aperture at slots, which is also used to remove the gas included in an aluminum die-casting production part, is set to 0.1 mm. JP-A-207848/1983 discloses the aperture size of 0.2 — 0.6 mm at each slot of a rotor. Further, in JP—A— 28556/1982, it is disclosed that each aperture has a taper shape of a width than 0.8 mm and a height of less than 0.8 mm.
JP-A-86060/1981 and JP-A-145753/1981, disclose that apertures at slots are provided at a rotor core, the electrical conductive material is casted in the slots, and the electrical conductive
material is removed from each aperture. In these techniques, the reduction of the stray load loss or the improvement of the power factor of a motor is aimed at by removing the electrically conductive material from each aperture at the slots.
An induction motor disclosed in JP-A-35665/1981 can decreases changes of a power factor and solves the hindrance of a duct composition. An induction motor according to JP-A-207848/1983 is improved in efficiency and productivity. Further, JP-A-28556/1982 a little makes mention to noise generation, but mainly explains tne scattering in parameters of slots. As a result, this reference only suggests some measurements for an efficiency improvement.
However, by results of experiements as to an induction motor operational performance, which had been executed by the inventors of the present invention, it was found that providing slots as disclosed in JP-A-86060/1981, JP-A-145753/1981, JP-A-35665/1981, JP-A-207848/1983, and JP-A-28556/1982 does not always improve the effieciency of an induction motor if the induction motor is used in an induction motor of a class from rated power 40 kw - 1000 kw.
Further, it was proved that, through depending on the width w, a peripheral direction length of each aperture of slots, the height h, a radial direction length of each aperture from surface of a rotor core to a motor bar, the narmonic secondary copper loss which composes parts of the noise and the stray load loss
sometimes increases. The increase of the oss is due to the increase of a pulsating component of a gap magnet flux, affected by the apertures of slots and complexly changing of the magnet flux flow in the rotor core, and further another cause, for example, the magnet saturation phenomena.
As mentioned above. in the existing techniques as for an induction motor, the quantitative examinations of the sizes of an aperture at a slot in order to reduce of the noise and the harmonic secondary copper loss have not been tried. Recently, an induction motor has been developed or produced on a priority of the low noise or downsized one. However, in this induction motor, a counter-measure for the harmonic secondary copper loss in not considered. Further, by merely providing each aperture of slots at a rotor core, the downsizing of an induction motor or its noise problem can not be solved. SUMMARY OF THE INVENTION An objective of the invention:
The present invention has been achieved in consideration of the above described problems, and is aimed at providing a high performance induction motor which can imorove the power factor and reduce the noise level and the stray load loss, by setting a size of each aperture at slots provided in a rotor core within an adequate region.
Methods Solving the Problem:
The inventors carried out many experiment of induction motors under the various environmental conditions in which an induction motor are operated. Thus, the inventors have discovered the adequate size range of an aperture at each slot, wherein the power factor can be improved, and the noise level and the stray load loss can be reduced. That is, the inventors have found that the power factor can be improved, and the noise and the stray load loss can be reduced, by setting so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 2 mm. Further, it is proved that an induction motor having the above-mentioned size as to an aperture at eacn slot is very effective for an induction motor of a class from 40 kw - 1000 kw. In the present invention, methods of increasing the performance of an induction motor are as follows.
(1) To attain the above-mentioned objective, based on the above-mentioned discovery by the experiments, the present invention provide an induction motor, comprising:
a stator; and
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the heifht h of the radial direction size is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 1 mm and less than 2 mm. (2) Further, the present invention provide an induction motor of a class from the rated power 40 kw - 600 kw, comprising:
a stator; and
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm less than 3.5 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 2 mm.
Moreover, the above-mentioned induction motor according to the present invention are also available to the rated power 40 kw - 1000 kw.
(3) Further, the present invention provides an induction motor comprising:
a stator; and
a rotor provided inside apart from the stator by a predetrm,ined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core anc connected to each slot in which is filled with a secondary conductor, continuously formed in a shaft direction,
said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the distance from a rotor surface to a second conductor face is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the distance from a rotor surface to a second conductor face is set in an interval of more than 1 mm and less than 2 mm.
(4) Further, in order to reduce only the noise level and the harmonic secondary copper loss, the present invention provides an induction motor, comprising:
a stator; and
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, in which is
filled with a secondary conductor, and the size of the aperture are set within a range composed of an interval of the width of more than 1 mm and less 3.5 mm and an interval of the height h of more than 1 mm and less than 3 mm.
(5) Further, the present invention provided an induction motor, comprising:
a stator; and
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor hawing a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, in which is filled with a secondary conductor, a concave sectional shape, being provided at a face contacting of an aperture bottom, of the secondary conductor in a slot (refer to Fig. 13), and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the heigth h of the distance from a rotor surface to a second conductor face i set in an interval of more than 1 mm and less than 1.5 mm, and i the width w of the peripheral direction size is more than 2 mm an
less than 3.5 mm, the height h of the distance from a rotor surface to a second conductor face is set in an interval of more than 1 mm and less than 2 mm.
(6) Further, the present invention provides an induction motor, comprising:
a stator; and
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continusously formed in a shaft direction, said aperture arranged at a predetermined interval in a peripheral direction of said rotor, in which is filled with a secondary conductor, a concave sectional shape, of which the height is set from 0.5 mm — 2.0 mm, being provided at a face contacting an aperture bottom, of the secondary conductor in each slot (refer to Fig. 13), and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the distance from a rotor surface to a bottom of said second conductor is set in an interval
of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the distance from a rotor surface to a bottom
of a second conductor is set in an interval of more than 1 mm and less than 2 mm.
(7) To attain the above—mentioned objective, based on the above-mentioned discovery by the experiments, the present invention provide an induction motor, comprising:
a rotor provided inside apart from the stator by a predetermined gap in the concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 2 mm.
(8) Further, the present invention provide an induction motor of a class from the rated power 40 kw - 600 kw, comprising:
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having
a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of saia rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, and the aperture are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the direction size is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3-5 mm, the height h of the radial direction size is set in an interval of more than 1 mm and less than 2 mm.
Moreover, the above-mentioned induction motor according to the present invention are also available to the rated power 40 kw - 1000 kw.
(9) Further, the present invention provides an induction motor, comprising:
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a perdetermined interval in a peripheral direction of said rotor, in which is filled with a secondary conductor, and the aperture are formed so that if the width w of the perioneral direction size is more than 1 mm and less than 2 mm, the height h of the distance from a rotor surface to a second conductor face is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the distance from a rotor surface to a second conductor face is set in an interval of more than 1 mm and less than 2 mm.
(10) Further, in order to reduce only the noise level and the harmonic secondary copper loss, the present invention provides an induction motor, comprising:
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined
interval in a peripheral direction of saidrotor, in which is filled with a secondary conductor, and the size of the aperture are set within a range composed of an interval of the width of more 1 mm and less 3.5 mm and an interval of the height h of more than 1 mm and less than 3 mm.
(11) Further, the present invention provides an induction motor comprising:
a rotor provided inside apart from the stator by a predetermined gap in a concnetric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, in which is filled with a secondary conductor, a concave sectional shape being provided at a a face contacting an aperture bottom, of the secondary conductor in a slot (refer to Fig. 13), and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the distance from a rotor surface to a second conductor face is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the distance from a rotor
surface to a second conductor face is set in an interval of more than 1 mm and less than 2 mm.
(12) Further, the present invention provides an induction motor, comprising:
a rotor provided inside apart from the stator by a predetermined gap in a concentric circle state, the rotor having a plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
wherein an aperture is provided at a surface zone of a rotor core and connected to each slot, continuously formed in a shaft direction, said aperture being arranged at a predetermined interval in a peripheral direction of said rotor, in which is filled with a secondary conductor, a concave sectional shape, of which the height is set from 0.5 mm - 2.0 mm, being provided at a face contacting an aperture bottom, of the secondary conductor in each slot (refer to Fig. 13), and the apertures are formed so that if the width w of the peripheral direction size is more than 1 mm and less than 2 mm, the height h of the distance from a rotor surface to a bottom of said second conductor is set in an interval of more than 1 mm and less than 1.5 mm, and if the width w of the peripheral direction size is more than 2 mm and less than 3.5 mm, the height h of the distance from a rotor surface to a bottom of a second conductor is set in an interval of more than 1 mm and less than 2 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a shaft direction sectional view of an induction motor of an embodiment according to the present invention.
Fig. 2 is a transverse sectional view of a part in which several slots and their apertures are provided.
Fig. 3 is a typical specimen graph showing a magnetic flux density distribution in a gap between a stator and a rotor.
Fig. 4 is a typical specimen graph showing a magnetic flux flow at an area in the vicinity of an aperture of a slot.
Fig. 5 is a graph showing measurement results of power factor ratios optained by using a width w of an aperture of a slot and a height of an aperture of a slot as measurement parameters, for the rated power 40 kw class induction motor.
Fig. 6 is a graph showing measurement results of power factor ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as measurement parameters, for the rated power 600 kw class induction motor.
Fig. 7 is a graph showing measurement results of noise level ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as measurement parameters, for the rated power 40 kw class induction motor.
Fig. 8 is a graph showing measurement results of noise level ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as measurement parameters, for the rated power 600 kw class induction motor.
Fig. 9 is a graph showing measurement results of harmonic secondary copper loss ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as measurement parameters, for the rated power 40 kw class induction motor.
Fig. 10 is a graph showing measurement results of harmonic secondary copper loss ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as measurement parameters, for the rated power 600 kw class induction motor.
Fig. 11 shows an adequate range of the size as to the width w and the height h of the aperture of each slot shown in Fig. 2, which the power factor is improved, the noise level and the harmonic secondary copper loss.
Fig. 12 shows a diagram a range as to the two parameters of the width and the height of an aperture, in which the noise level and the harmonic secondary capper loss are reduced.
Fig. 13 shows, another example of a sectional shape of a slot with an aperture, in which an aperture bottom surface contacting a face secondary conductor contained in a slot is driven into the conductor and formed as a concave sectional shape. DETAILED DESCRIPTION OF THE EMBODIMENT
Hereinafter, the present invention will be explained in details with reference to embodiments shown in the drawings.
Again, the contents of the above-mentioned figures can be summarized as follows.
Fig. 1 is a shaft direction sectional view of an induction motor of an embodiment according to the present invention, and Fig. 2 is a transverse sectional view of a part in which several slots their apertures are provided. Fig. 3 is a typical specimen graph showing the magnetic flux density distribution in a gap between a stator and a rotor. Further, Fig. 4 is a typical specimen graph showing a magnetic flux flow at an area in the vicinity of an aperture of a slot. Fig. 5 is a graph showing test results of power factor ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as test parameters, for the rated power 40 kw class induction motor, and Fig. 6 is a graph showing test results of power factor ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as test parameters, for the rated power 600 kw class induction motor. Further, Fig. 7 is a graph showing test results of noise level ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as test parameters, for the rated power 40 kw class induction motor, and Fig. 8 is a graph showing test results of noise level ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as test parameters, for the rated power 600 kw class induction motor. Furthermore, Fig. 9 is a graph showing test
results of harmonic secondary copper loss ratios obtained by using the width w of an aperture of a slot and the height h of an aperture of a slot as test parameters, for the rated power 40 kw class induction motor, and Fig. 10 is a graph showing test results of harmonic secondary copper loss ratios obtained by using the width w of an aperture of a slot and the height h of a slot as test parameters, for the rated power 600 kw class induction motor. Fig. 11 shows an adequate range of the size as to the width w and the height h of the aperture of each slot shown in Fig. 2, in which the power factor is improved, the noise level and the harmonic secondary copper loss. Fig. 12 shows a diagram showing a range as to the two parameters of the width and the height of an aperture, in which the noise level and the harmonic secondary copper loss are reduced. Further, Fig. 13 shows, another example of a sectional shape of a slot with an aperture, in which an aperture bottom surface contacting a face secondary conductor contained in a slot is driven into the conductor and formed as a concave sectional shape.
An induction motor is composed of a cylindrical stator and a rotor 1 rotationally and concentrically arranged on a shaft of the motor (not shown in figures) inside the cylindrical stator.
The stator possesses a cylindrical stator core combined with a stator frame provided on the stator, in which a box for flowing cooling gas is provided, and a winding wire is wound on the stator core. In the stator frame, fans (not showing figures) are
installed in order to removing the neat generated in the rotor 1 and the stator.
The rotor 1 has a rotor core 2 laid onto a rotary axis 6 (a shaft). The rotor 1 is supported by bearing provided via blankets provided at the two ends of the stator frame.
On the outer face part of the rotor core 2, a plurality of slots 3 continuously formed in a shaft direction, into which conductive material is casted. Further, these slots which have conductive material, from rotor conductors 4, namely, winding wire rotor parts. A current flowing route is provided by combining the rotor conductors 4 by two short circuit rings 5a and 5b provided at both ends of the rotor cores 2.
On the outer face part of the rotor core 2, a plurality of slots 3 continuously formed in the shaft direction, an aperture 8 is formed and connected to each slot.
Aperture 8 are formed by machining upper parts of slots after a plurality of slots 3 are prepared and casted in with conductive material. In another method of aperture forming. an aperture connected to a slot is prepared in the rotor core, and conductive material is casted into each of an aperture and a slot. However, in this method, since conductive material is also remaining in each aperture, the noise level or the stray load loss due to the harmonic secondary current considerably increases. Therefore, in the embodiment, the aperture 8 are made by the former method, so there is removed the conductive malarial from
each aperture. The physical property exisiting each aperture is the same as the property existing between the stator and the rotor
In the case of slots without any aperture, the height of a magnet bridge part is reduced to as lowly as possible while the strength of the bridge part is kept, in order to prevent the temperature of the rotor from increasing due to the increase of the first and second current in the core of the upper part of a rotor conductor 4, which functions as a magnetic bridge increasing a leakage of magnet flux which remarkably decreases the power factor. The power factor of an induction motor predominantly depends on a slot leakage reactance mainly determined by a cross sectional shape of the rotor slot, if the structure other than the cross sectional shape of each slot in the rotor 1 is the same. If a leakage reactance other than the slot leakage reactance is remarkably large, the power factor and the motor efficiency degrade due to the increase of the first current and the second current. Especially, if there is not exist any aperture 8 for the slots, since the magnetic bridge causes a magnetic short circuit state, the slot leakage reactance increases due to the increase of leakage flux. On the other hand, if the apertures 8 of slots are provided as shown in the embodiment, since the slot leakage flux is largely reduced in comparison with the case of no aperture of a slot, it is possible to considerably increase the power factor.
However, if the aperture of slots are provided, it is assumed that the following problem is caused. That is, as shown in Fig. 3, if the aperture S of slots are prepared, since the permeance distribution in the gap becomes nonuniform, pulsating components of the magnetic flux in the gap increases, compared with the case of a slot without an aperture. Consequently, effects of the increases of the harmonic electro-magnetic forces come as remarkable, and the noise level increases.
Moreover, as shown in Fig. 4, it is known that, under operational conditions of an induction motor, the magnetic flux (9a, 9c) does not input perpendicularly to the surface of the rotor, namely, not in the accurate radial direction, but inputs in the oblige direction to the surface of the rotor. Therefore, in the case of an induction motor having apertures of slots, the magnetic flux component 9a of the magnetic flux 9 input into a rotor conductor 4 through a rotor core 2 is input to a rotor conductor 4 via a rotor core 2. On the other hand, the magnetic flux component 9a of the magnetic flux 9 is directly input to a rotor conductor 4 via a rotor core 2. The harmonic magnetic flux wave of the magnetic flux component 9a is attenuated by the core 2, but the magnetic flux 9b directly inputting into the rotator conductor 4 increases the harmonic secondary copper loss, because the attenuation of the harmonic flux wave is small.
The above-mentioned noise or the harmonic secondary copper loss can be reduced by increasing the radial driectipn distance
from the surface of the rotor to the secondary conductor in a slot as shown in Fig. 2, namely, the height h of an aperture of a slot in a rotor. This is becasue the noise is reduced due to the decrease of pulsating components of the magnetic flux density by adjusting influences of magnetic force generating force of the rotor, and the harmonic secondary copper loss is reduced to the fact that magnetic flux including harmonic components is prevented from directly inputting into the head part of the rotor conductor. However, the increase of an aperture h possibly prevent the power factor increase since the increase of an aperture h may increase the second leakage reactance.
In the above-mentioned consideration of operational characteristics of an induction motor, the inventors selected and measured the power factor, the noise level and the harmonic secondary copper loss as performance parameters in connection with an aperture of a slot of, as changing the parameters. As results, it was found by the measurements, that an adequate (or effective) area as to the parameters of the width w and the height h of an aperture of a slot exists. Moreover, the discovered area of the width and the height of an aperture, is also proved to be available for an iduction motor of a class of the rated power 40 kw — 1000 kw.
Hereafter, mainly, the measurement results of as to the power factor, the noise level and the harmonic secondary copper loss, will be explained for an induction motor of the rated power 40
kw and the rated power 1000 kw. In experimental measurements for an induction motor, 32 cases of measurements are carried out by selecting 8 parameters values as to the width w, which are determined by dividing the range from 1.0 mm to 4.0 mm by a 0.5 mm step, including a case of 0 mm of the width, and selecting 4 parameter values of 0.5 mm, 1.0 mm, 2.5 mm and 3.0 mm as to the height interval from 0.5 mm and 3 mm. Each test piece is produced a machining process.
In Figs. 5 and 6, each measured value is normalized by the usual value measureed for a usual induction motor with an aperture of the 0 mm height or the 0.5 mm height, which actually possesses no aperture of a slot. In these figures, the measured value points than a value 1.0 are connected with solid lines. Measured value points less than a value 1.0 are connected with a dotted line.
As shown in Figs. 5 and 6 showing measurement result as to an induction motor of the rated power 40 kw, the measurement results show that the leakage reactance is reduced and the power factor is increased by providing an aperture to each slot, although its effects depends on the height of the aperture of a slot. Further, it was found that if the height is more than 2.5 mm, the power factor is less than the normalized standard value 1.0. However, the power factor exceeds the normalized standard value 1.0. However, the height of an aperture h is less than 2 mm, the power factor exceeded the normalized standard value 1.0,
if the width is more than 2 mm. The above-mentioned measurement results for an induction motor of a class of the rated power 600 kw showed almost the same tendency as the measurement result tendency shown in Fig. 5 for the induction motor of the rated power 40 kw, although the values themselves of the measurement results are different between the experiment for the 40 kw motor and the experiment for the 600 kw.
From the above-mentioned results shown in Figs. 5 and 6, it is effective that if the width w of an aperture of each slot is more than 1 mm and less 2 mm, the height h is to be set in an interval from 1 mm to 1.5 mm, and if the width w of an aperture of each slot is more than 2 mm, the height h is set in an interval from 1 mm to 1.5 mm.
Further, the measurement results of the noise level for the induction motor systems of a class of 40 kw and a class of 600 kw are explained as follows. In Figs. 7 and 8, the measured values are also normalized in the same manner as the manner explained in Figs. 5 and 6. In Figs. 7 and 8 also, points of measured values more than the standard normalized vlaue 1.0 are connected with solid lines. other points of measured values less than the value 1.0 are connected with dotted lines.
As shown in Fig. 7, in an induction motor of the rated power 40 kw, the noise level increases if an aperture of a slot is provided and the width w of the aperture is increased, because pulsating components of the magnetic flux density in a gap is
increased due to the increase of the width w of the aperture as explained previously. However, as for the height more than 1.0 mm of an aperture, the noise level decreased below the standard normalized value 1. In the case of the 1 mm height, it was found that the noise level ratio becomes less than the standard normalized value 1 if the width w of an aperture of a slot is less than 3.5 mm. As shown in Fig. 8, the above mentioned measurement results for an induction motor system of a class of 600 kw showed almost the same tendency as the measurement result tendency shown in Fig. 7 for the induction motor of 40 kw, although the values themselves of the measurement results are different between the experiment for the 40 kw motor and the experiment for the 600 kw.
From the above-mentioned results, it is effective to set the width w of an aperture of each slot less than 3.9 mm, and the range of the height h more than 1.0 mm and less than 3 mm.
Further, measurement results of the harmonic secondary copper loss is explained in the following, the measurement being carried out in the same measurement range as to the height and width of an aperture of a slot as the range for measuring the power factor and the noise level. Further, the measurement results of the harmonic secondary cpper loss for the induction motor of a class of 40 kw and a class of 600 kw are explained as follows. In Figs. 9 and 20, the measured values are also normalized in the same manner as the mentioned for the above-mentioned measuring
method explanatior. In these figures, points of measured values less the standard normalized value 1 are connected with solid lines. On the other hand, points of measured values less than the value 1 are connected with dotted line.
As mentioned in Fig. 9, there is a width of an aperture of a slot, at which the harmonic secondary copper ratio has the minimum value for a height of an aperture of a slot. This tendency occurs for every heights.
The phenomena, as shown in Fig. 9, in which there is a width causing the minimum value of the harmonic secondary copper loss for each height is caused by the following characteristics of an aperture of a slot. At first, the decreases of the harmonic secondary copper loss to the minimum value is caused by the decrease of the second current itself flowing in the rotor conductor, which is also caused by the decrease of the first current due to the decreases of a leakage reactance with the increase of the width in an aperture of a slot. After the minimum point, the increase of the width in an aperture of a slot increase influences of the magnetic component 9b directly inputting into the rotor conductor 4.
As explained, in Fig. 9, the harmonic secondary copper loss has the minimum value for each height of an aperture of a slot within an interval in the width of an aperture of 1 mm — 3.3 mm, and the harmonic secondary copper loss is less than the normalized value 1 when the height of an aperture of a slot is 1
mm. The above-mentioned measurement results for an induction motor of a class of 600 kw showed almost the same tendency as the measurement result tendency shown in Fig. 9 for the induction motor of 40 kw, although the values themselves of the measurement results are different between the experiment for the 40 kw motor and the experiment for the 600 kw motor.
It can be realized that the harmonic secondary copper loss is kept less than the standard normalized value 1, by setting the width within an interval from 1 mm and 3.5 mm, and the height within an interval from 1 mm to 3 mm, for an aperture of a slot provided in an induction motor.
As mentioned, it is proved that there is an adequate region as to the width and height of an aperture of a slot, in which the power factor, the noise level and the harmonic secondary copper loss are considerably improved. Thus, an adequate regions improving the power factor, the noise level and the harmnonic secondary copper loss are summarized in Fig. 11, based on the measurement results shown in Figs. 5 - 10, respectively.
In Fig. 11 in which an axis of ordinate is expressed by the height, and an axis of abscissa is expressed by the width. An adequate region for the three performance (characteristics) parameters improvement, in which if the width w of an aperture of each slot is more than 1 mm and less 2 mm, the height h is to be set in an interval from 1 mm to 1.5 mm, and if the width w of an aperture slot is more than 2 mm and less 3.5 mm, the height h is
set in an interval from 1 mm to 2 mm, is illustrated in Fig. 11. That is, Fig. 11 shows the abvoe-mentioned adequate region shown by a hooked rectangular a,b,c,d,e and f (a hexagon with a right angle at each apex) which is a region superimposed by three regions expressed by three regions hatched by three different hatching manners. If an operational point of an induction motor according to the present invention is set in the hexagon region shown in Fig. 11, the power factor, the noise level and the harmonic secondary copper loss all can be improved.
In the above-mentioned region, the minimum value of the width of an aperture at a slot was prescribed by results of the power factor measurement, and the maximum value of the height was prescribed by measurement results of the noise level and the harmonic secondary copper loss. Further, the minimum value of the height of an aperture at a slot was prescribed by measurement, results of the noise level and the harmonic secondary copper loss measurement, and the maximum value of the height of an aperture at a slot was prescribed by measurement results of the power factor.
If only the noise level and the harmnonic secondary copper loss have only to be reduced, the size of an aperture at a slot is set within a rectangular region a,b,c and d shown in Fig. 12, of a width interval from 1 mm to 3.5 m and a height interval from 1 mm to 3 mm, based on the measurement results shown in Figs. 7 —10. Further, if an operational point of an induction motor according
to the present invention is set in the rectangular region shown in Fig. 12, the noise level and the harmonic secondary copper loss all can be improved.
Although not shown in figures and explained, the same performance measurement were carried out for an induction motor of a class of the rated power 40 kw to the rated power 1000 kw. From the measurement results, although values gained by the measurements are different in the absolute values, the adequate region of the sizes of an aperture at a slot is almost the same as the region for the above-mentioned 40 kw - 600 kw class induction motor.
By applying the above-mentioned embodiment, the induction motor of a class from the rated power 40 kw to the rated power 1000 kw, in which an aperture is to be formed so that if the width w of an aperture of each slot is more than 1 mm and less 2 mm, the height h is to be set in an interval from 1 mm to 1.5 mm, and if the width w of an aperture of each slot is more than 2 mm and less 3.5 mm, the height h is set in an interval from 1 mm to 2 mm, which improves the power factor, the noise level and the harmonic secondary copper loss. Therefore, by using an induction motor according to the present invention, it is possible to improve the noise level and the stray load loss together with the power factor.
Thus, if the above-prescribed region of the sizes of an aperture at a slot is applied to an induction motor of a class from the rated power 40 kw to the rated power 1000 kw, it is possible to provide a high performance induction motor or a rotor used in the induction motor which remarkably reduces the noise level and the stray loss.
Moreover, another embodiment according to the present invention will be explained by referring to Fig. 13.
Fig. 13 shows another example of a sectional shape of a slot with an aperture. As shown in Fig. 2, a plurality of slots 3 are provided in a rotor at the predetermined interval in a peripheral direction of said rotor, and on the outer face zone of the rotor core 2, the plurality of slots 3 continuously formed in the shaft direction, into which conductive material is casted. Further, conductive material is casted in each of slot 3, which form the rotor conductors 4, namely, winding wire rotor parts.
Further, an aperture 8 connected to each slot 3, which is provided at the outer face zone of the rotor core 2, continuously in the shaft direction, is formed by a machining process. Furthermore, in this embodiment, a concave sectional shape is continuously formed in the shaft direction in the rotor conductor 4. As to the size of the aperture 8 (strictly speaking, concave sectional shape), an aperture is to be formed so that if the width w of an aperture of each slot is more than 1 mm and less 2 mm, the height h including the height or depth of the concave in
the rotor conductor 4 h is to be set in an interval from 1 mm to
1.5 mm, and if the width w of an aperture of each slot is more
than 2 mm and less 3.5 are, the height h is set in an interval
from 1 mm to 2 mm.
As devised in this embodiment, if an aperture of a slot is
machined so as to form a concave in the rotor conductor 4, the
distance from the outer surface of a rotor core 2 to the outer
surface of a rotor conductor 4, that is, h - h , is shorter than
the distance from the outer surface of a rotor core 2 to the
outer surface without a concave in a rotor conductor 4.
Therefore, the permeance ratio which is obtained by adding 0.66
to the value obtained by dividing the distance from the outer
surface of a rotor core 2 to the outer surface of a rotor
conductor 4, h - h, with the width w of an aperture of a slot
becomes smaller in comparison with the rotor without an aperture
not forming a concave shape in the rotor conductor 4. Thus, the
leakage reactance, proportional to the permeance ratio, can be
reduced.
Therefore, in this embodiment. the following performance
improvements can be attained. That is , it is possible to
improve the power factor whereas the noise level and the stray
loss (the harmonic secondary copper loss) can be decreased.
Moreover,, since the slot leakage reactance is reduced, the power
factor can be more improved.
In the above-mentioned embodments, the composition and characteristics of an induction motor in which conductive material is casted, namely an induction motor of die-casting slot in a rotor core, has been explained. Naturally, a rotor with a rotor conductor into which a conductor is driven has the same good performance.
As mentione abvoe, the present invention can provide a high performance induction motor and a rotor, which can considerably improves the power factor and reduces the noise level and the stray loss, by setting the sizes of an aperture of each slot within the above-disclosed adequate regions.
WE CLAIM
1. A high performance induction motor, comprising: a stator: and
a rotor provided inside apart from said stator by a predetermined gap in a concentric circle state, said rotor having a ;plurality of slots, continuously formed in a shaft direction, which are arranged at a predetermined interval in a peripheral direction of said rotor;
characterized in that an aperture is provided at a surface
zone of said rotor and connected to each slot, continuously
formed in a shaft direction, said aperture being arranged at a
perdetermined interval in a peripheral direction of said rotor,
and each aperture is formed so that if a width (w) in a
peripheral direction of a rotor axis is more than 1 mm and less
than 2 mm, a radial height (h) of an aperture is to be set in a
range of more than 1 mm and less than 1.5 mm, and if the width
(w ) of each apertures is more than 2 mm and less tnan 3.5 mm, the
radial height (h) of an aperture is to be set in a range of more
than 1 mm and less than 2 mm.
2. "The induction motor as claimed in claim 1 wherein the size of
each said apertures is set in a ranoe of a width (w) of said
aperture in a peripheral direction size of more than 1 mm and
less than 3.5 mm, and a height (h) of said aperture in the
radial direction size of more than 1 mm and less than 3 mm".
3. "The induction motor as claimed in the preceding claims
wherein said aperture is provided at a surface zone of said rotor
and connected to each slot in which is filled with a secondary
conductor, and a concave sectional shape being provided at said
secondary conductor in each slot and each aperture is formed so
that if the width in a peripheral direction of a rotor axis is
said w, the radial distance from a surface of said rotor to a
bottom of said concave is to be set at said h, and if the width
of each aperture is said w, the radial distance from a surface
of said motor to a bottom of said concave is to be set at said
h ". 4. "The induction motor as claimed in the preceding claims
wherein a concave sectional shape of which a height is set from 0.5 mm - 2.0 mm is provided at said secondary conductor in each slot".
5. The induction motor as claimed in any one of claims 1-4, wherein said aperture is formed by a machining process.
6. "The induction motor as claimed in any one of the preceding claims wherein each aperture part is formed by a machining process after said secondary conductor is filled in each slot".

Each aperture of a plurality of slot in a rotor core are arranged at the predetermined interval on the surface part in the peripheral direction, which are continuously formed in the shaft direction. By setting such sizes of the aperture that if the width in the peripheral direction of a rotor axis is more 1 mm and less 2 mm, the radial height of an aperture is to be set in an interval more 1 mm and less 1.5 mm, and if the width in the peripheal direction is more 2 mm and less 3.5 mm, the radial height of an aperture is to be set in an interval more 1 mm and less 2 mm. Moreover. If it is desired to reduce only the noise level and the harmonic secondary copper loss, the size of the aperture are to be set within a region formed of the width in the peripheral cirection more than 1 mm and less than 3.5 mm, and the height in the radial direction more than 1 mm and less than 3 mm.