Rotors and electric rotating machines.

Abstract

DEPCT64 The rotor will include a rotor shaft (21) with rotor slots (22) that are molded into it. The rotor slots will The rotor conductor (23), which is the rotor channel conductor (22), includes the inner channel (26), which is The first channel, and the outer channel (27) which is the second channel, the second channel is connected to the first channel and will It is closer to the outer surface (25) of the rotor shaft (21) than it is to the first slot. The edge (26a) on the side of the outer surface of the second channel will have an edge (27a) on the opposite side. With the outer surface(25), the electric current flowing through the rotor conductor(23) will include The basic element is one that has the same frequency as the driving frequency for the rotor in the range between... The edge (26a) of the first channel and the outer surface (25) are larger than the surface depth of The basic elements between the edge (27a) of the second channel and the outer perimeter surface (25) will Smaller than the surface depth. -----------------------------------------------------------

Description

Rotor and Rotating Electric Machine

[0001] The present invention relates to a rotor which is a double-cage rotor and a rotating electric machine having the rotor.

[0002] In an induction type rotating electric machine, a double-cage rotor is widely used in order to increase the starting torque generated when the rotating electric machine starts. The cage rotor has a rotor conductor which is a conductor housed in a rotor slot of a rotor core, and two short-circuit rings connected to the rotor conductor. In the rotor slots of the double-cage rotor, an inner slot located on the center side of the rotor core and an outer slot located on the outer peripheral surface side of the rotor core are provided. In the double-cage rotor, the current flowing through the rotor at the time of starting is concentrated in the outer slot, and the resistance of the current flowing through the rotor is increased, whereby the starting torque is increased.

[0003] The electrical energy losses in a rotating electric machine include primary copper loss which is a loss caused by the resistance component of the winding provided in the stator, secondary copper loss which is a loss caused by the resistance component of the rotor conductor, and iron loss which is a loss caused by the magnetic flux linking the stator core and the rotor core. In addition, so-called harmonic secondary copper loss, which is a loss caused by the harmonic flux due to the stator slots linking the rotor conductor, is also regarded as one of the electrical energy losses in the rotating electric machine. The harmonic flux is generated by the current of the harmonic component, which is a component having a frequency higher than the driving frequency of the rotor, flowing through the rotor core. The high-frequency component is a component that does not contribute to the driving of the rotor.

[0004] Patent Document 1 discloses a technique of inserting a conductor having a conductivity different from that of the rotor conductor into one of the inner slot and the outer slot in order to obtain a desired starting torque without reducing the driving efficiency of the rotating electric machine.

[0005] Japanese Patent Laid-Open No. 1-252144

[0006] In the configuration disclosed in Patent Document 1, leakage current may occur from the rotor slots due to the arrangement of the inner and outer slots of each rotor slot. Also, the starting torque may decrease due to the arrangement of the inner and outer slots. For this reason, the technology of Patent Document 1 has the problem that the driving efficiency of the rotating electric machine may decrease due to the generation of leakage current.

[0007] The present invention has been made in view of the above, and aims to provide a rotor that can improve the driving efficiency of a rotating electric machine.

[0008] To solve the above-mentioned problems and achieve the objective, the rotor according to the present invention has a rotor core in which rotor slots for housing conductors are formed. The rotor slots include a first slot and a second slot located on the outer circumferential side of the rotor core and connected to the first slot. The distance between the outer circumferential side end of the first slot and the outer circumferential surface is greater than the skin depth of the fundamental wave component, which is the component of the current flowing through the conductor with the same frequency as the rotor's driving frequency, and the distance between the outer circumferential surface end of the second slot and the outer circumferential surface is smaller than the skin depth.

[0009] The rotor according to the present invention has the effect of improving the driving efficiency of a rotating electric machine.

[0010] Cross-sectional view of a rotating electric machine according to Embodiment 1 of the present invention; Side view of the rotating electric machine shown in Figure 1; Diagram showing a portion of the rotor core of the rotating electric machine shown in Figure 1 where one rotor slot is provided; Diagram showing the main part of a rotating electric machine according to Embodiment 2 of the present invention.

[0011] Below, a rotor and a rotating electric machine according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to this embodiment.

[0012] Embodiment 1. Figure 1 is a cross-sectional view of a rotating electric machine 100 according to Embodiment 1 of the present invention. The rotating electric machine 100 is a three-phase induction motor having a double-cage rotor. The rotating electric machine 100 comprises a cylindrical stator 10, a rotor 20 surrounded by the stator 10 and driven by rotation, and a shaft 30 provided at the center of the rotor 20. The rotor 20 is a double-cage rotor. Figure 1 shows a cross-section perpendicular to the central axis AX, which is the center of rotation of the rotor 20. In Figure 1, hatching indicating the cross-section is omitted. The direction in which the central axis AX extends is sometimes called the axial direction, and the direction along the circle centered on the central axis AX is sometimes called the circumferential direction.

[0013] The stator 10 has a stator core 11 in which a plurality of stator slots 12 for housing windings are formed. The stator core 11 is constructed by stacking a plurality of silicon steel plates, which are magnetic materials, in the axial direction. The stator core 11 has a back yoke 15 and a plurality of stator teeth 14 that protrude from the back yoke 15 toward the rotor 20. Each stator tooth 14 is spaced apart from each other in the circumferential direction. The stator slots 12 are provided between each stator tooth 14. The stator slots 12 are open spaces toward the rotor 20. Stator coils 13, which are formed by windings, are arranged within the stator slots 12. A grid power supply of 50 Hz or 60 Hz is directly connected to the stator coils 13.

[0014] The rotor 20 has a rotor core 21 in which a plurality of rotor slots 22 are formed, in which rotor conductors 23 are housed. The rotor core 21 is constructed by laminating a plurality of silicon steel plates, which are magnetic materials, in the axial direction. A gap is provided between the outer circumferential surface 25 and the stator 10. The outer circumferential surface 25 is the surface of the rotor core 21 that is away from the central axis AX. A plurality of rotor teeth 24 are provided on the portion of the rotor core 21 that is on the outer circumferential surface 25 side. Each rotor tooth 24 is spaced apart from each other in the circumferential direction. The rotor slots 22 are provided between each rotor tooth 24. The rotor slots 22 are closed spaces in the plane shown in Figure 1. The rotor conductors 23 are arranged in each rotor slot 22. The material used for the rotor conductors 23 is a non-magnetic metallic material such as aluminum or an aluminum alloy.

[0015] Figure 2 is a side view of the rotating electric machine 100 shown in Figure 1. The rotating electric machine 100 is equipped with two short-circuit rings 40 arranged along the circumferential direction. One short-circuit ring 40 is connected to the rotor conductor 23 at one end of the rotor core 21 in the axial direction. The other short-circuit ring 40 is connected to the rotor conductor 23 at the other end of the rotor core 21 in the axial direction.

[0016] Figure 3 shows a portion of the rotor core 21 of the rotating electric machine 100 shown in Figure 1, where one rotor slot 22 is provided. The rotor slot 22 has an inner slot 26 which is a first slot, an outer slot 27 which is a second slot connected to the first slot, and a slit 28 connecting the inner slot 26 and the outer slot 27.

[0017] The inner slot 26 is the portion of the rotor slot 22 located on the central axis AX side. The outer shape of the inner slot 26 is such that the width of the inner slot 26 in the circumferential direction narrows towards the central axis AX side, and the portion on the central axis AX side and the portion on the outer circumferential surface 25 side are rounded. The outer shape of the inner slot 26 is not limited to the shape shown in Figure 3 and can be any shape.

[0018] The outer slot 27 is located closer to the outer circumferential surface 25 than the inner slot 26. The outer shape of the outer slot 27 is circular. The diameter of this circle is smaller than the maximum width of the inner slot 26 in the circumferential direction. The outer shape of the outer slot 27 is not limited to a circle and can be arbitrary.

[0019] The slit 28 is provided between the end 26a of the inner slot 26 on the outer peripheral surface 25 side and the end 27a of the outer slot 27 on the opposite side from the outer peripheral surface 25 side, i.e., the end on the central axis AX side. The width of the slit 28 in the circumferential direction is narrower than the maximum width of the inner slot 26 in the circumferential direction and also narrower than the maximum width of the outer slot 27 in the circumferential direction.

[0020] The narrowing of the width in the slit 28 reduces the magnetic resistance in the slit 28. This reduction in magnetic resistance in the slit 28 increases the inductance in the inner slot 26. When the rotating electric machine 100 is started, the current flowing through the rotor 20 is concentrated in the outer slot 27, increasing the electrical resistance flowing through the rotor 20. As a result, the rotating electric machine 100 increases its starting torque.

[0021] In addition to the fundamental wave component current, which has the same frequency as the rotor 20's drive frequency, the rotor core 21 also contains harmonic components, which are components of the current flowing through the rotor core 21 with frequencies higher than the rotor 20's drive frequency. These high-frequency components do not contribute to the driving of the rotor 20. The high-frequency components are generated due to the number of stator slots 12 formed in the stator core 11 and the stator coils 13.

[0022] Let σ be the conductivity of the rotor conductor 23, μ be the magnetic permeability of the rotor conductor 23, and ω be the angular frequency of the alternating current driving the rotor 20. The skin depth Hf of the fundamental wave component of the current flowing through the rotor conductor 23 is expressed by the following equation (1).

[0023]

[0024] The distance H1 between the end 27a of the outer slot 27 and the outer surface 25 is smaller than the skin depth Hf. The distance H2 between the end 26a of the inner slot 26 and the outer surface 25 is larger than the skin depth Hf. That is, the relationship H1 < Hf < H2 holds. The skin depth is defined as the distance between the surface and the position where the current density is 1 / e of the current density at the surface of the conductive material when an electric current flows through it. "e" is the base of the natural logarithm. The skin depth is considered an indicator of the skin effect, in which current is concentrated on the surface of the conductive material as the frequency increases.

[0025] If the relationship H1 > Hf holds true, then in the rotor slot 22, current flows only to the outer slot 27 due to the skin effect. In this case, during starting, the current flowing to the rotor 20 is concentrated in the outer slot 27, increasing the resistance of the current flowing to the rotor 20 and thereby increasing the starting torque. On the other hand, because no current flows to the inner slot 26 and the current is concentrated in the outer slot 27, the leakage current leaking from the rotor slot 22 to the outside of the rotor slot 22 increases.

[0026] Furthermore, if the relationship Hf > H2 holds, current flows to both the outer slot 27 and the inner slot 26, thus reducing the leakage current in the rotor slot 22. On the other hand, as the current flowing to the rotor 20 is diffused to the outer slot 27 and the inner slot 26, the resistance of the current flowing to the rotor 20 decreases, thus reducing the starting torque.

[0027] In Embodiment 1, by satisfying the relationship H1 < Hf < H2, leakage current in the rotor slot 22 can be suppressed and starting torque can be increased.

[0028] According to Embodiment 1, the distance H2 between the end 26a and the outer circumferential surface 25 is made greater than Hf, which is the skin depth of the fundamental wave component, and the distance H1 between the end 27a and the outer circumferential surface 25 is made smaller than Hf. This suppresses leakage current in the rotor slot 22 and increases the starting torque. The rotating electric machine 100 can improve its driving efficiency by suppressing leakage current and increasing the starting torque. As a result, the rotor 20 has the effect of improving the driving efficiency of the rotating electric machine 100.

[0029] Embodiment 2. Figure 4 shows the main parts of the rotating electric machine 100 according to Embodiment 2 of the present invention. In Embodiment 2, the rotor conductor 23 and the rotor conductor 50 are housed in the inner slot 26. Figure 4 shows the portion of the rotor core 21 of the rotating electric machine 100 in which one rotor slot 22 is provided. In Embodiment 2, the same reference numerals are used for the same components as in Embodiment 1, and the differences from Embodiment 1 will be mainly described.

[0030] The rotor conductor 23, which is the first conductor, is made of aluminum or an aluminum alloy. The rotor conductor 50, which is the second conductor, is a conductor with higher conductivity than the rotor conductor 23. The rotor conductor 50 is made of copper or a copper-based alloy. In Figure 4, the rotor conductor 50 is surrounded by the rotor conductor 23. The rotor conductor 50 is located in the inner slot 26 on the AX side of the central axis. In Figure 4, the outer shape of the rotor conductor 50 is rectangular. The outer shape of the rotor conductor 50 in the cross-section shown in Figure 4 may be other than rectangular.

[0031] By providing rotor conductor 50, which has higher conductivity than rotor conductor 23, within the inner slot 26, the resistance of the current flowing through the rotor slot 22 is reduced compared to the case where only rotor conductor 23 is housed in the inner slot 26. This reduces secondary copper loss caused by the resistance components of rotor conductors 23 and 50.

[0032] According to Embodiment 2, the rotor 20 can improve the driving efficiency of the rotating electric machine 100, similar to Embodiment 1, and can reduce secondary copper loss by the arrangement of the rotor conductors 50. By reducing secondary copper loss, the rotor 20 can further improve the driving efficiency of the rotating electric machine 100.

[0033] The configurations shown in the above embodiments are merely examples of the content of the present invention, and can be combined with other known technologies. It is also possible to omit or modify parts of the configuration without departing from the spirit of the present invention.

[0034] 10 Stator, 11 Stator core, 12 Stator slots, 13 Stator coil, 14 Stator teeth, 15 Back yoke, 20 Rotor, 21 Rotor core, 22 Rotor slots, 23, 50 Rotor conductors, 24 Rotor teeth, 25 Outer surface, 26 Inner slots, 26a, 27a ends, 27 Outer slots, 28 Slit, 30 Shaft, 40 Short-circuit ring, 100 Rotating electric machine.

Claims

DEPCT641. A rotor consisting of a rotor core with rotor slots molded into it, a rotor core containing electrical conductors, where the rotor slots include the first and second slots, the second slot is closer to the outer surface of the rotor core than the first slot, the second slot is connected to the first slot, and the first slot has an edge on one side of the outer surface, and the second slot has an edge opposite to the outer surface, the current flowing through the electrical conductors includes the basic element which has a frequency equal to the driving frequency for the rotor, the range between the edge of the first slot and the outer surface is greater than the surface depth of the basic element, and the range between the edge of the second slot and the outer surface is smaller than the surface depth.

2. A rotor according to claim 1, where the electrical conductors have conductivity sigma and permeability mu, the alternating current driving the rotor has an angular frequency omega, and the surface depth, denoted by Hf, is given in the formula (1) below.[Formula 1]Hf=(Formula)3.A rotor under claim 1 or 2, in which the primary electrical conductor is the primary conductor, and the first slot contains primary and secondary electrical conductors with higher electrical conductivity than that of the primary conductor.

4. An electrically rotating machine comprising: a stator including a stator core with stator slots molded in it, stator slots containing winding wires; and a rotor under any of claim 1 through 3 driven by the rotor, a rotor enclosed by the stator.