JPH02219445A - Induction motor with magnetically anisotropic rotor - Google Patents

Abstract

PURPOSE:To suppress pulsation of torque, vibration or noise even when a motor is driven through a non-sinusoidal power source and to improve the electrical characteristic by applying a power conduction skin composed of magnetic and non-magnetic composite material on the outer face of a rotor core block such that the circumferential component of permeability is larger than the radial component thereof. CONSTITUTION:A rotor 2 comprises a rotor shaft 6, a rotor core 7 composed of thin magnetic boards such as silicon steel boards laminated axially, and a power conduction skin 8 to be secured to the outer face of the rotor core. Gear type thin iron boards 11 composed of magnetic material such as iron are laminated axially such that the circumferential component of permeability of the power conduction skin 8 is larger than the radial component thereof, and a conductor 12 having high conductivity such as copper or aluminum conductor is casted in the gap of lamination. By such arrangement, pulsation of torque, vibration or noise can be suppressed even when the motor is driven through a non-sinusoidal power source, and a good electrical characteristic can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in induction motors, and particularly to improvements in induction motors that do not have winding slots on the rotor surface.

[Conventional technology]

In general, the rotor of an induction motor has a slot in the rotor core and a wound rotor in which the rotor winding is housed, and a wound rotor in which the rotor core is provided with a slot and the rotor winding is housed in the slot. There are three types of rotors: a squirrel-cage rotor that houses the conductor, a rotor with the rotor core itself acting as a conductor, and a block-type rotor with the conductor fixed to the entire surface of the rotor core. be. Of these, squirrel cage rotors are most commonly used because they are robust, relatively inexpensive, and have good electrical characteristics.

However, this squirrel cage rotor also has drawbacks such as torque pulsation and large vibration and noise. In other words, the stator side of this type of induction motor consists of a stator core and stator windings housed in slots provided in the core, but since the magnetic permeability is different between the teeth and the slots, the space is small. This generates harmonics, which are incident on the rotor, and harmonic currents are induced in the rotor's winding conductors.The harmonic magnetic flux generated by this, and the harmonic magnetic flux due to the winding slots on the rotor side, are transmitted to the stator. This is because harmonic electromagnetic force acts on the side and prevents the rotor from rotating smoothly.

One possible way to suppress this electromagnetic force is to skew the rotor winding conductors, but recently, this type of induction motor is powered by a variable frequency power supply using an inverter.
As the speed has come to be controlled, this skew countermeasure alone is no longer sufficient. That is,
Since an inverter power supply is usually composed of semiconductor circuits, the voltage or current is a non-sinusoidal wave, so the magnetic flux of the induction motor has more
Contains many harmonics, rotor skew can only cancel out specific harmonics, and many other harmonics of the same level remain, resulting in increased torque pulsation and vibration noise. .

On the other hand, a block rotor without winding slots in the rotor has this advantage. In other words, since the block rotor does not have slots on the outer periphery of the rotor, harmonic magnetic flux is not generated by the slots, and the entire rotor functions both as an iron core through which magnetic flux passes and as a conductor through which current flows. Since the entire surface of the rotor becomes a current path, it can be considered that skew is applied most effectively to the entire surface of the rotor. Torque pulsation and vibration noise are extremely small even when actually driven by an inverter power source. This has been confirmed through experiments.

However, the block-shaped rotor has a disadvantage in that its electrical characteristics are inferior to that of the squirrel-cage rotor. That is, JP-A-62-
53161, Japanese Patent Application Laid-Open No. 63-140504, etc., all of the block rotors have a structure in which magnetic thin plate iron cores are laminated in the axial direction and a non-magnetic material is cast between the layers. Therefore, the magnetic flux flows in the circumferential direction so as to pass through the shortest distance on the rotor surface, and leakage magnetic flux tends to increase, which has the disadvantage of impeding electrical characteristics. Further, as other rotor structures, structures described in Japanese Patent Application Laid-Open No. 57-46656 and Japanese Patent Application Laid-open No. 57-71254 have also been devised. However, in this case, it is difficult to increase the excitation reactance due to the low space factor of the magnetic core, which serves as a path for magnetic flux, and thus it is difficult to improve the electrical characteristics.

[Problem to be solved by the invention]

As described above, the squirrel cage rotor has excellent electrical characteristics, but has problems with torque pulsation and vibration noise.

Further, although the block-shaped rotor has less torque pulsation and vibration noise, it has problems such as poor electrical characteristics.

For this reason, there has been a desire for an induction motor that exhibits both of these characteristics, that is, low torque pulsation and low movement noise, and excellent electrical characteristics.

An object of the present invention is to provide an induction motor of this type that has low 1-herk pulsation and vibration noise, and has good electrical characteristics even when driven by a non-sinusoidal power source using an inverter power source. .

[Means to solve the problem]

In other words, in the present invention, in a block-shaped rotor, an energized material is made of a composite of magnetic and non-magnetic materials so that the outer surface of the rotor core has a magnetic permeability larger in the radial direction component than in the circumferential direction component. The above object was achieved by providing an outer skin, providing a plurality of slits in the tooth portion of the magnetic material constituting the current-carrying outer skin, and then laminating both in the circumferential direction.

[Effect]

The magnetic material constituting the current-conducting outer skin of the block-shaped rotor is easier to manufacture and can have a larger iron space factor if it is made of gear-shaped thin iron plates laminated rather than in the shape of a crest. However, in this method, since the teeth of the gear-shaped thin iron plate are aligned in the circumferential direction, a large amount of leakage magnetic flux flows in the circumferential direction, which impairs the electrical characteristics.

Therefore, by twisting the entire upper tooth, which has multiple radial slits in the teeth of a gear-shaped thin iron plate, the outer diameter of the tooth is so that the parts are laminated in the circumferential direction.

This reduces leakage magnetic flux at the outer circumferential portion of the current-carrying outer skin, shortens the path of induced current, and reduces secondary resistance.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

In FIG. 1, an induction motor with a stator ↓ and a rotor I is shown partially in section. The stator 1 includes a stator frame 3, a stator core 4, and a stator winding 5. As shown in a partially broken view in FIG. 2, the rotor 1 includes a rotor core 7 made of a rotating shaft 6 and magnetic thin iron plates such as silicon steel plates arranged on the rotating shaft, laminated in the axial direction. The current-carrying outer skin 8 is fixed to the outer surface of the rotor core.

This rotor fork is rotatably supported by the stator frame 3 via a bearing 9. Further, a fan 10 for cooling is fixed to the rotating shaft 6 and rotates together with the rotating shaft.

The current-carrying outer skin 8 of the rotor is shown partially enlarged in FIG. For example, gear-shaped thin iron plates 11 made of a magnetic material such as iron are laminated in the axial direction, and a conductor 12 made of a highly conductive material such as copper or aluminum is cast into the gap between the laminated thin iron plates 11. Configure. A gear-shaped thin iron plate 11 shown in FIG. 3 protrudes radially from an inner diameter bottom portion 13 in contact with the first rotor core 7, and a toothed portion 14 serving as an outer peripheral portion is made of an integral thin iron plate. Teeth 14
, from the outer diameter part to a position near the inner diameter bottom part 13,
A plurality of slits 15 are provided. As shown, the tooth portion 14 is twisted in the direction of the arrow and has a shape substantially perpendicular to the bottom of the inner diameter. Thus, even if the inner diameter bottom portion 13 is laminated in the axial direction, the tooth portions 14 on the outer peripheral portion are laminated in the circumferential direction.

The magnetic flux emitted from the magnetic poles of the stator core enters the gear-shaped thin iron plate, passes through the rotor core, follows the magnetic path from the gear-shaped thin iron plate at a position opposite to the other pole, and returns to the stator core, and then passes through the gear-shaped thin iron plate. Since the tooth portions are laminated in the circumferential direction, magnetic resistance in the circumferential direction increases, and leakage magnetic flux flowing in the circumferential direction on the outer circumferential surface of the rotor is suppressed.

Furthermore, since the teeth of the porous thin iron plate are aligned in the axial direction, the resistance of the conductor forming the flow path of the induced current is reduced by shortening the flow path.

According to this embodiment, leakage magnetic flux is reduced and induced current is increased.

Note that by providing multiple slits in the teeth of the gear-shaped thin iron plate, the effect is slightly reduced even if the teeth are not twisted in the axial direction, but it is still useful for improving electrical characteristics. Not even.

〔Effect of the invention〕

According to the present invention, leakage magnetic flux is reduced and effective magnetic flux is increased,
Since the secondary resistance is reduced and the induced current is increased, the generated torque is increased and the efficiency is improved, which is effective in improving the electrical characteristics of the induction motor.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an induction motor according to an embodiment of the present invention;
FIG. 2 is a partially cutaway perspective view of a block-shaped rotor according to the present invention;
FIG. 3 is a partially enlarged view of the magnetic thin iron plate that composes the current-carrying outer sheath. DESCRIPTION OF SYMBOLS 1... Stator, 2... Rotor, 4... Stator core, 5... Stator winding, 6... Rotating shaft, 7... Rotor core, 8... Electrifying outer skin, 11... gear-shaped thin iron plate,
12... Conductor, 13... Inner diameter bottom of gear-shaped thin iron plate,
14... Outer diameter tooth portion of gear-shaped thin iron plate.

Claims (1)

[Scope of Claims] 1. A stator including a stator core and a stator winding, a rotating shaft rotatably supported within the stator, and a rotating shaft disposed on the rotating shaft and together with the rotating shaft. The rotor core includes a rotor core that rotates, and a current-carrying outer skin fixed to the outer peripheral surface of the rotor core, and the current-carrying outer skin is made of a magnetic material such that its magnetic permeability is larger in the radial direction than in the circumferential direction. An induction motor equipped with a magnetically anisotropic rotor characterized in that it is made of a magnetically anisotropic material that is a composite material with a non-magnetic material. 2. The current-carrying outer skin is formed by laminating gear-shaped thin iron plates and using a non-magnetic material with good conductivity filled between adjacent spaces between the gear-shaped thin iron plates. Induction motor with magnetically anisotropic rotor. 3. An induction motor equipped with a magnetically anisotropic rotor according to claim 2, wherein a plurality of slits are provided in the teeth of the gear-shaped thin iron plate constituting the current-carrying outer skin. 4. An induction device equipped with a magnetically anisotropic rotor according to claim 2 or 3, characterized in that the teeth of the gear-shaped thin iron plates constituting the current-carrying outer skin are twisted and laminated. Electric motor.