JPH11307354A - High efficiency and high speed rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high efficiency and high speed rotary machine by that the core of at least the rotor or stator comprises an Si steel sheet having an Si concn. higher by specified wt.% or more in a surface layer than in the sheet thickness center and rotation speed is specified rpm or more. SOLUTION: The rotary machine has a rotation speed of 7000 rmp or more, the core of at least the rotor or stator comprises an Si steel sheet having an Si concn. higher by 0.3 wt.% or more in a surface layer than in the sheet thickness center and rotation speed is specified rpm or more. To provide an Si concn. gradient in the sheet thickness direction, such a method is used as e.g. the surface of an Si steel sheet is coated with an Si paste and it is thermally diffused, Si ion is deposited by the PVD and thermally diffused, or high temp. gas of SiCl4 . etc., is blown on the steel, sheet to deposit Si and it is thermally diffused by the thermal VCD, and the mean Si content is pref. about 6 wt.% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter-driven high-speed rotating machine used in fields such as home appliances, information, automobiles, industrial equipment, and electric power.

[0002]

2. Description of the Related Art In recent years, permanent magnets have been used as rotor magnets, or SPMs containing a magnet in a part of the rotor.
(Surface Permanent Magnet) motor and IPM (Interior
or Permanent Magnet) motors, or reluctance motors whose rotors do not include magnets (switched reluctance (SR) motors, synchronous (synchronous) reluctance motors, homopolar (bipolar) motors), and the like have been put into practical use.

[0003] In these motors, various improvements and
Development has been carried out, but all of these efforts have been focused on optimal switching and inexpensive sensing technology, as well as on motor structure design that maximizes efficiency by suppressing copper loss, mechanical loss, noise, etc. Despite being a major component of the motor, little has been considered.

Further, recently, a number of high-speed rotating motors and generators have been studied for the purpose of downsizing and labor saving of the apparatus, but they are still in practical use and have various problems. .

For example, high-speed generators are being put to practical use with SPM, but NdFeB is used as a permanent magnet for the rotor.
A magnet is considered to be one of the most suitable materials, and it is necessary to suppress the rotor temperature to about 100 ° C. in order to exhibit its magnetic properties. To that end, select an iron core material with a small iron loss for the stator. There is a need.

[0006] Among SR motors that use reluctance torque, it is effective to increase the speed of the SR motor in order to reduce the size of the motor. this is,
This is because bearing accuracy and heat generation (iron loss) from the iron core are serious problems, and motor efficiency is poor.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to provide a high-efficiency high-speed rotating machine.

[0008]

SUMMARY OF THE INVENTION The present inventors have investigated the current of such a high-speed rotating machine such as a high-speed motor or a generator in order to reduce iron loss which accounts for a large weight of the loss. Generally, in the case of a high-speed rotating machine of about 10,000 to 100,000 rpm, the fundamental frequency is about 150 Hz to 5 kHz, depending on the type and the number of poles of the rotating machine, and a multiple of the harmonic and ripple current due to switching are reduced. Superimpose.

According to the results of the study by the present inventors, it has been found that a conventional high-grade non-oriented silicon steel sheet is not sufficient to improve the efficiency of such a high-speed rotating machine. Si
When the content is increased, the electric resistance increases, the eddy current is suppressed, and high-frequency iron loss can be reduced.
wt. % Silicon steel sheet is considered to be one of the most suitable iron core materials, but is somewhat inferior to the conventional non-oriented silicon steel sheet in workability and saturation magnetic flux density.

In the case of high-speed rotation, the magnetic flux density is not always high because the motor is used at a low torque, and the influence of the saturation magnetic flux density is considered to be considerably smaller than that of a normal (medium-low speed) rotating machine. It is desirable that the saturation magnetic flux density be high at the edge because the effective area is small.

Therefore, the high-frequency iron loss is low and 6.5 w
t. As a result of studying an iron core material capable of improving the defect of the% silicon steel sheet, formation of a Si concentration gradient in the sheet thickness direction, more specifically, 0.3 wt. It has been found that, by increasing the percentage by% or more, the high-frequency iron loss caused by the high-frequency current can be significantly reduced as compared with the conventional silicon steel sheet, and the saturation magnetic flux density is high and the workability is also good.

The present invention has been made on the basis of such findings. At least one of the cores of the rotor and the stator has a surface layer whose Si concentration is 0.3 wt. % Or more silicon steel plate, and rotation speed is 7
A high-efficiency high-speed rotating machine characterized by being at least 000 rpm.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The rotating machine targeted by the present invention has a rotation speed of 700.
0 rpm or more, and at least one core of the rotor and the stator has a surface layer whose Si concentration is 0.3 wt. % Or more.

In general, as the amount of Si in iron is increased, the soft magnetic properties are improved, and 6.5 wt. %, But the difference in Si concentration between the surface layer and the center is 0.3 wt. % Or more,
A difference appears between the magnetic permeability of the surface layer and the magnetic permeability of the central part. In the case of a uniform Si material, an eddy current flows over the entire surface perpendicular to the direction of the magnetic flux. Therefore, the eddy current loss varies greatly depending on the plate thickness. However, if there is a difference in the magnetic permeability between the surface layer and the center to some extent, the magnetic flux is likely to be confined in the surface layer, and the eddy current flows dispersedly at two places on the front and back surfaces.
An effect as if sandwiched between sheets is obtained. For this reason, it can be considered that iron loss is reduced.

The difference in Si concentration between the surface layer and the center is 0.3 wt.
%, The effect of reducing such iron loss cannot be sufficiently obtained. Therefore, in the present invention, the Si concentration in the surface layer is 0.3 wt.
% Or more. When the Si concentration difference was 4 wt.
%, The hysteresis loss increases extremely,
4 wt. % Or less is preferable.

Several methods are conceivable for forming a Si concentration gradient in the thickness direction. For example, by depositing a Si ions by a method or PVD performing thermal diffusion after coating the Si paste on the surface of the pure iron or silicon steel sheet, a method to likewise thermally diffused or by blowing hot gas such as SiCl ₄ in the steel sheet, Si CVD after thermal diffusion
(Silicone method). In particular, the last thermal CVD method is the most practical method. FIG. 1 shows the Si concentration distribution in the thickness section of the steel sheet prepared by the thermal CVD method. At this time, the steel plate had a thickness of 0.1 mm and an iron loss W1 / 10k (10 kHz, 0.1 kHz).
Iron loss value at 1 T) was 7.2 W / kg. As shown in this figure, it can be seen that a concentration gradient of Si is formed in the thickness direction by thermal CVD. Note that this Si distribution is
Electron probe microanalyzer (EPM
A) can be grasped.

In any of the above methods, a high silicon steel sheet having a uniform Si concentration in the thickness direction, for example, 6.5 wt. % Silicon steel sheet requires thermal diffusion, which requires a longer furnace line length, a lower line speed, or a combination of both. However, when the Si concentration gradient is formed in the thickness direction as in the present invention, the diffusion is stopped in the middle, so that such a disadvantage is solved. Therefore, the uniform 6.
5 wt. It has a cost advantage over the% silicon steel sheet.

The switching frequency has a different driving range and ripple frequency depending on the switching element such as IGBT, GTO, MOS-FET, etc., but the motor to which the present invention is applied exhibits its effect at 1 kHz or more.

As the average Si content is increased, the high-frequency iron loss is suppressed and the motor efficiency is improved. However, the workability is deteriorated and the saturation magnetic flux density is reduced. % Or less is preferable. From the viewpoint of punching properties, when a material having a high surface Si concentration and a low center Si concentration is used as the core material as in the present invention, the center has ductility, so that cracks are unlikely to occur, and the surface layer is hard. Burrs generated at the time of punching can be reduced.

[0020]

[Embodiment] Capacity 10 kW, rated speed 100,000 rpm
m, a generator was produced using an NdFeB magnet for the two-pole rotor and a core material shown in Table 1 for the stator, and the production cost and the stator temperature (corresponding to the efficiency) under the same load conditions were grasped. . Incidentally, the switching frequency of the power supply was 20 kHz. The evaluation criteria for the production cost are based on the processing cost of a 3% silicon steel plate (0.1t) for press punching and caulking, and the same as ◎, the cost increase within 10% is ○, and the cost increase is 1
0% or more and 50% or less △, cost increase is 50% or more and 1
A value of 00% or less was evaluated as x.

[0021]

[Table 1]

As shown in Table 1, a generator using a silicon steel sheet having a Si concentration difference defined in the present invention as a core of a stator has a low stator temperature, therefore has a high efficiency and a low production cost. confirmed.

[0023]

As described above, according to the present invention,
A high-efficiency high-speed rotating machine with high efficiency and low production cost can be obtained.

[Brief description of the drawings]

FIG. 1 shows Si in a thickness direction of a silicon steel sheet used in the present invention.
The figure which shows a density distribution.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Katsushi Kasai 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd.

Claims (1)

[Claims] 1. The method according to claim 1, wherein at least one of the cores of the rotor and the stator has a surface layer whose Si concentration is 0.3 wt. % Or more silicon steel plate, and the rotation speed is 70
A high-efficiency, high-speed rotating machine characterized by being at least 00 rpm.