JPH09322437A - Rotating machine core and rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotating machine core and a rotating machine having low loss and small temperature rise by providing an Si content of an electromagnetic steel plate constituting the core lower than a specified amount, providing a mean crystal grain size larger than a specified size, or providing an average number of crystal grains in a plate thickness direction lower than a specified number. SOLUTION: Si content of an electromagnetic steel plate constituting a core 1 is made lower than 1wt.%, average grain size of electromagnetic steel plate is more than 0.1mm, or the average number of grains in a plate thickness direction is less than 4. This core 1 comprises a rotating machine core, and the plate thickness of the electromagnetic steel plate is desired to be less than 0.4mm. Also in the rotating machine, the exciting frequency for the core 1 is desired to be less than 100Hz for a time period more than 80% of the driving time for the rotating machine. In this way, by inhibiting the Si content of the electromagnetic steel plate, saturated magnetization can be increased. Also, by increasing the average crystal grain size of the electromagnetic steel plate or reducing the average number of the crystal grains in the plate thickness direction, the magnetic permeability of the electromagnetic steel plate can be increased and the loss of a core exciting winding (no-load copper loss) can be reduced.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a stator of a rotating machine or a core of a rotor.

[0002]

2. Description of the Related Art Non-oriented electrical steel sheets are generally used for the core of rotating machines. In a small motor or the like, since the non-oriented electrical steel sheet is required to have a high magnetic flux density, the Si content is reduced and the saturation magnetization is increased. Since the electrical steel sheet having a low Si content has low electric resistance and large eddy current loss, the ratio of hysteresis loss to iron loss is small. Therefore, in the electrical steel sheet with a low Si content, it is not necessary to increase the crystal grain size of the electrical steel sheet that affects the hysteresis loss. For this reason, it is generally desirable for the electrical steel sheet having a low Si content that the crystal grain size is small from the viewpoint of workability. For a rotating machine requiring high efficiency, an electromagnetic steel sheet having a high Si content and a large crystal grain size is used in order to reduce iron loss.

Recently, rotary machines have been reduced in size and weight centering on servomotors. The decision to reduce the size and weight is
Drive current. To increase the output and reduce the size and weight, it is necessary to pass as much drive current as possible. The limit of this drive current is determined by the temperature rise of the rotating machine, which is related to the temperature limit of the windings through which the current flows and the sensor, and the temperature rise at which thermal expansion is a problem. In order to suppress this rise in temperature, it is important to suppress iron loss and copper loss as well as to remove the heat generated by these losses. The core contributes significantly to heat removal from the rotating machine. Therefore, in order to improve the performance of the rotating machine, a core with low loss and good heat dissipation is required.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rotary machine core and a rotary machine with low loss and small temperature rise.

[0005]

The rotating machine core of the present invention has a magnetic steel sheet forming the core having a Si content of 1% by weight or less, and an average steel grain size of 0.1 mm or more. Alternatively, it is characterized in that the average number of crystal grains in the plate thickness direction is 4 or less.

In the above rotary machine core, it is preferable that the thickness of the electromagnetic steel sheet is 0.4 mm or less.

The rotating machine of the present invention is characterized in that the core is the rotating machine core. In the above rotating machine, it is preferable to set the excitation frequency of the core to 100 Hz or less for a time of 80% or more of the rotating machine drive time. Further, it is preferable that the core is made of an electromagnetic steel plate having a plate thickness of 0.2 mm or less and the excitation frequency of the core is 300 Hz or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The rotating machine according to the present invention is an electric motor or a generator, and the core is an armature core or a field yoke (or a field core) of these rotating machines. The core material is an electromagnetic steel plate, and is mainly composed of pure iron, extremely soft steel, silicon steel plate or other iron. In the present invention, in order to improve heat removal, an electromagnetic steel sheet having high heat conductivity is used. Pure iron has the highest thermal conductivity, but in the present invention, S
The i content is set to 1% by weight or less, and the thermal conductivity is set to about 1/2 or more of that of the ultra-soft steel. Magnetic steel sheets having a Si content of 1% by weight or less are relatively easy to manufacture.

In order to suppress the temperature rise of the rotating machine, it is necessary to reduce iron loss as well as high thermal conductivity. In the present invention, the hysteresis loss is suppressed by setting the average crystal grain size of the magnetic steel sheet to 0.1 mm or more or the average number of crystal grains in the plate thickness direction to 4 or less. The average crystal grain size is the average value of the crystal grain size with respect to volume or cross-sectional area. Since the larger the average crystal grain size is, the smaller the hysteresis loss is, the larger the average grain size, the better. The average crystal grain size of the electromagnetic steel sheet is 0.
If it is 1 mm or more, the hysteresis loss is 1 for Si content.
It can be set to 1/2 or less of the hysteresis loss of the conventional main electrical steel sheet which is less than or equal to wt%.

When the plate thickness is 0.1 mm or less, iron loss rapidly increases due to the influence of the surface. Moreover, when the average number of crystal grains in the plate thickness direction exceeds 4, the influence of the crystal grains becomes larger than the influence of the surface of the electrical steel sheet. By setting the average number of crystal grains to 4 or less, iron loss can be reduced.

The thickness of the conventional main magnetic steel sheet having a Si content of 1% by weight or less is 0.5 mm. Plate thickness 0.4
If it is less than or equal to mm, the eddy current loss can be reduced to about 2/3 or less of that of the above-mentioned main magnetic steel sheets.

As described above, the saturation magnetization B _S is increased by suppressing the Si content of the electromagnetic steel sheet. Further, if the average crystal grain size of the electromagnetic steel sheet is increased or the average number of crystal grains in the plate thickness direction is reduced, the magnetic permeability of the electromagnetic steel sheet increases and the loss of the core excitation winding (copper loss without load) decreases.

The rotating machine of the present invention uses the core configured as described above as the field core or the armature core. In order to improve the heat removal property, the core of the present invention is used as the core that plays an important role in heat dissipation. For example, in the case of an inner rotor, the core of the present invention is used for the outer stator core or yoke. For the outer rotor,
The core of the invention is used for the outer rotor core or yoke.

In a rotating machine operating at low speed, the ratio of hysteresis loss to iron loss is high. In the rotating machine of the present invention, using the core, the time is 80% or more of the driving time of the rotating machine,
The excitation frequency of the core is 100 Hz or less. Generally, the hysteresis loss is proportional to the excitation frequency, and the eddy current loss is proportional to the square of the excitation frequency. With commercially available magnetic steel sheets,
The hysteresis loss and the eddy current loss are substantially equal at the excitation frequency of 100 Hz, and the hysteresis loss becomes larger than the eddy current loss at the excitation frequency of less than 100 Hz. Although the eddy current loss increases with a low Si content magnetic steel sheet, the excitation frequency is 10
By setting it to 0 Hz or less, the total iron loss becomes small.
The excitation frequency of a low-speed rotating machine is generally 200 to 30.
It is 0 Hz. At 200 Hz, which is twice as high as 100 Hz, the iron loss becomes about 3 times. As described above, when the excitation frequency is 100 Hz or less for 80% or more of the rotating machine driving time, the increase in iron loss can be suppressed within 50%. As a low-speed motor, for example, there is a drive motor for an electric vehicle.

The eddy current loss ratio (= eddy current loss / hysteresis loss) is approximately proportional to the square of the plate thickness × frequency. Therefore, the eddy current loss ratio is high in a rotating machine operating at high speed. In this invention, the exciting frequency of the core is a high-speed rotating machine of 300 Hz or more, and the thickness of the electromagnetic steel sheet is 0.2 mm or less. Since the eddy current loss ratio is approximately proportional to the square of the plate thickness x frequency, the eddy current loss ratio of the high-speed rotating machine configured as described above is a standard core (plate thickness 0.5 m
Made of electromagnetic steel sheet of m, the excitation frequency is almost equal to the eddy current loss ratio at the commercial frequency of 50 Hz). Examples of high-speed motors include servo motors and compressor drive motors.

[0016]

【Example】

(Example 1) In the brushless DC motor shown in FIG. 1, the armature core 1 was changed in material and tested. The characteristics of the electromagnetic steel sheet in each test are shown in Table 1 together with the performance of the armature core 1. The rotor 3 is made of a cylindrical permanent magnet.

[0017]

[Table 1]

With low rotational speed driving, the eddy current is small. Therefore, the electromagnetic steel sheet having a thickness of 0.35 mm according to the present invention (Example A of the present invention in Table 1) has a conventional thickness of 3% Si of 0.3%.
Since the saturation magnetization is higher than that of the 5 mm electromagnetic steel sheet (conventional example F in Table 1), the exciting current is small and the thermal conductivity that determines the heat removal property is high. The hysteresis loss is almost the same as that of the conventional core. If the temperature rise affects only the thermal conductivity of the armature core, the temperature rise can be 1/3 or less. Explaining with FIG. 1, even if the winding loss due to the drive current flowing through the armature winding 2 is constant, the heat generated by the winding loss passes through the armature core 1 and the case 4 to the outside as indicated by reference numeral 6 in the figure. As it is released, the temperature rise will be lower. The heat generated by the core iron loss is naturally radiated to the outside through the armature core 1 and the case 4 as indicated by reference numeral 7 in the figure. Of the iron loss, the hysteresis loss is the same in the present invention example A and the conventional example F, and therefore the temperature rise is low with respect to the heat generation due to the hysteresis loss.
In general, eddy current loss is inversely proportional to electrical resistivity, and thermal conductivity is proportional to electrical conductivity (= 1 / electrical resistivity), that is, thermal conductivity is proportional to eddy current loss. In the case of low rotation driving, the eddy current loss is small, but even if the thermal conductivity is low, the temperature rise hardly changes. Conventional 0.3% Si plate thickness 0.5 m
In the case of the m 2 electromagnetic steel sheet (conventional example G in Table 1), the thermal conductivity is high, but the hysteresis loss is large, so the temperature rise is higher than in the invention example B.

(Embodiment 2) At high speed rotation, eddy current loss increases. In the electromagnetic steel sheet having a plate thickness of 0.2 mm according to the present invention (Example B of the present invention in Table 1), the conventional plate thickness of 3% Si is 0.1.
Compared with the case of 2 mm electromagnetic steel sheet (conventional example E in Table 1), the eddy current loss is large, but the thermal conductivity is high. It is considered that there is no difference in the temperature rise due to the eddy current loss, but if the winding loss (copper loss) due to the drive current is the same, the invention sample B has a high thermal conductivity, so the temperature rise is low.

[0020]

According to the present invention, since the magnetic permeability of the rotating machine core is high and the hysteresis loss is also low, the exciting current can be kept low compared with the conventional core using the low Si electromagnetic steel sheet, and the temperature rise can be prevented. small. Further, the rotating machine core of the present invention has a high thermal conductivity and is excellent in heat removal, so that the temperature rise is small. Therefore, when the rotating machine core of the present invention is used, if the limiting temperature is constant, a large amount of drive current can be passed or the magnetic flux density of the core can be increased, so that the output of the rotating machine can be improved or the size can be reduced. .

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a rotating machine in which the present invention is implemented.

[Explanation of symbols]

 1 Armature core 2 Armature winding 3 Rotor (field) 4 Case 6 Flow of heat generated by armature winding current (driving current) 7 Flow of heat generated by core loss

Claims (5)

[Claims] 1. The electromagnetic steel sheet constituting the core has a Si content of not more than 1% by weight, and the electromagnetic steel sheet has an average crystal grain size of 0.
A rotating machine core characterized by having a size of 1 mm or more or an average number of crystal grains in the plate thickness direction of 4 or less. 2. The rotating machine core according to claim 1, wherein the electromagnetic steel sheet has a thickness of 0.4 mm or less. 3. A rotating machine, wherein the rotating machine core comprises the core according to claim 1. 4. The rotating machine according to claim 3, wherein the excitation frequency of the core is 100 Hz or less in a time of 80% or more of the rotating machine drive time. 5. The rotating machine according to claim 3, wherein the core is formed of an electromagnetic steel plate having a plate thickness of 0.2 mm or less, and the excitation frequency of the core is 300 Hz or more.