JP2001248639A - Stator unit of magnetic bearing and control type magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stator unit of a magnetic bearing reducing eddy current loss and a control type magnetic bearing. SOLUTION: A coil 4 for control current and a coil 5 for bias current are provided on an electromagnet 3. When a rotary body 1 rotates stably, a bias current is reduced, and a magnetic field generated by the coil 5 for bias current is weakened to reduce eddy current loss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic bearing.

[0002]

2. Description of the Related Art In a power storage device that stores power by rotation of a flywheel, a control type magnetic bearing is used to support a rotating body that is integral with the flywheel in a non-contact manner. Conventionally, in such a control type magnetic bearing, an electromagnet of the magnetic bearing is controlled by a current obtained by adding or subtracting a control current to or from a predetermined bias current. For example, when a bias current Io and a control current Ic are applied to a pair of electromagnets of a radial magnetic bearing arranged in the radial direction of the rotating body, a current Io + Ic is supplied to one of the electromagnets.
The current Io-Ic is supplied to the other electromagnet. Therefore,
The total current consumed by the pair of electromagnets is always 2Io regardless of the magnitude of the control current. It has also been considered that a magnetic field corresponding to the above-described bias current is provided by a permanent magnet.

[0003]

In the conventional control type magnetic bearing as described above, the pair of electromagnets consumes a certain amount of power based on the bias current even when the rotating body rotates stably and its swing is very small. are doing. Therefore, a relatively large eddy current loss based on the magnetic flux of the bias current occurs. This is the same even when a permanent magnet is used. When the eddy current loss occurs, the rotating body receives a negative torque, and the rotation speed gradually decreases. Therefore, even if the rotation speed of the rotating body is increased by the surplus power at night, the rotation may not be able to be continued until daytime.

[0004] In view of the above-mentioned conventional problems, an object of the present invention is to provide a stator unit of a magnetic bearing and a control type magnetic bearing that reduce eddy current loss.

[0005]

According to the present invention, a stator unit of a magnetic bearing includes a stator housing disposed around a rotating body, and a circumferential direction opposed to the rotating body by being supported by the stator housing. A plurality is arranged,
Each of them is provided with an electromagnet having a control current coil and a bias current coil (claim 1).
In the stator unit of the magnetic bearing configured as described above, since the bias current coil is provided separately from the control current coil, the bias current can be arbitrarily changed. Therefore, the bias current can be reduced according to the rotation state of the rotating body.

[0006] In the stator unit of the magnetic bearing, the electromagnet may be arranged so that an inner end face facing the rotating body is continuously arranged in a circumferential direction. In this case, the magnetic field generated by the electromagnet is continuous without interruption in the circumferential direction. Therefore, the change in the magnetic field is reduced.

Further, the control type magnetic bearing of the present invention has a plurality of electromagnets for supporting the rotating body in a non-contact manner, each electromagnet having a control current coil and a bias current coil; Based on the displacement of the body, the control current and the bias current are supplied to the control current coil and the bias current coil, respectively, to control the position of the rotating body, and reduce the bias current when the rotation of the rotating body is stabilized. A control device is provided (claim 3). In the control type magnetic bearing configured as described above, since the bias current coil is provided separately from the control current coil, the bias current can be arbitrarily changed separately from the control current. When the rotation of the rotating body is stabilized, the control device reduces the bias current.

[0008]

FIG. 1 is a plan view of a main structure of a stator unit of a magnetic bearing according to a first embodiment of the present invention, as viewed from an axial end of a rotating body 1. FIG. This rotating body 1
Is integrated with a flywheel (not shown) of the power storage device. In the figure, a cylindrical stator housing 2 arranged around a rotating body 1 has a homopolar electromagnet 3 constituting a radial magnetic bearing with respect to the rotating body 1.
Are two (in this example, two axes (X, Y), a total of four (X1,
X1 ', Y1, Y1')). Each electromagnet 3 is provided with a control current coil 4 and a bias current coil 5 separately.

FIG. 2 is a block diagram showing a configuration of a control type magnetic bearing employing the above-described stator unit. The control device of the magnetic bearing includes a displacement sensor 6, an A / D converter 7, a DSP (digital signal processor). 8, D /
A converter 9, amplifiers 10, 11 and rotation sensor 12
It has. Note that only one pair of the electromagnets 3 is shown. In the figure, the displacement (the amount of whirling) of the rotating body 1 during rotation is detected by a displacement sensor 6. The analog displacement signal output from the displacement sensor 6 is converted by the A / D converter 7 into a digital displacement signal,
Is input to The DSP 8 outputs a control signal for controlling the electromagnet together with the bias signal based on the input digital displacement signal. The control signal is converted into an analog value by the D / A converter 9 and supplied to the amplifier 10. The amplifier 10 applies control currents + Ic, -Ic having different signs to each other to the pair of coils 4 by forward / inverting amplification. On the other hand, the bias signal is converted into an analog value by the D / A converter 9 and supplied to the amplifier 11. The amplifier 11 amplifies the bias current Io.
Is given to the pair of coils 5. As a result, a magnetic field corresponding to the current Io + Ic is generated on one side of the electromagnet 3, and a magnetic field corresponding to the current Io-Ic is generated on the other side. Thereby, the position of the rotating body 1 is controlled so as to reduce the displacement. The rotation speed of the rotator 1 is detected by the rotation sensor 12 and a pulse signal corresponding to the rotation speed is output from the DSP 8.
Is input to

The bias current Io is not a constant value,
It is a variable value controlled by the DSP 8. DSP8
Indicates that the rotating speed of the rotating body 1 has reached a predetermined value or more and the whirling amount of the rotating body 1 is equal to or less than a predetermined threshold value, that is, it is recognized that the rotating body 1 is rotating stably. In this case, the bias signal is changed so as to reduce the bias current Io so that the whirling amount does not exceed the threshold value. In this case, since the stable rotation state has already been established, the stable rotation state can be maintained even if the bias current Io decreases. The power consumption decreases due to the decrease in the bias current Io. In addition, the decrease in the bias current Io reduces the eddy current loss, and the negative torque acting on the rotating body 1 decreases. As a result, the rotating body 1 continues to rotate with low power consumption for a long time without substantially reducing the rotating speed. Therefore, by increasing the rotation speed of the rotating body 1 using the surplus power at night, the rotation can be continued until daytime. Although FIG. 2 shows a configuration in which the bias current Io is applied to the pair of coils 5, other control axes exist in the control-type magnetic bearing (normally, there are five axes), and the control-type magnetic bearings have these axes. Bias current Io
Are equal to each other, if all the coils are connected in series and a current is supplied from one amplifier 11, the power consumption can be further reduced.

FIG. 3 is a diagram showing a simplified cross section along the axial direction of the rotating body 1 in the stator unit of the magnetic bearing according to the embodiment. As shown in the figure, the homopolar electromagnet 3 has coils 4, 5 on a horseshoe-shaped core 3a.
Is wound. A target 1a made of a magnetic material having higher specific resistance than a silicon steel plate is provided on a portion of the rotating body 1 facing the core 3a. The magnetic pole is connected to the core 3a
Assuming that the upper side is N and the lower side is S, a magnetic path A passing through the core 3a and the target 1a is formed as shown. The magnetic configuration of the electromagnet 3 is the same for all four electromagnets 3 shown in FIG. Therefore, the change of the magnetic field H of the target 1a when the rotating body 1 makes one rotation is as shown in FIG. Such a change in the magnetic field H has a large fluctuation range between the peak value and 0, and thus eddy current loss occurs. The next embodiment is to reduce the eddy current loss.

FIG. 5 is a plan view of the main configuration of the stator unit of the magnetic bearing according to the second embodiment, as viewed from the axial end of the rotating body 1. The difference from the first embodiment is that the inner end faces of the core of the electromagnet 3 are arranged without any gap in the circumferential direction. The rest is the same as the first embodiment, and the configuration of the control type magnetic bearing using this stator unit is also the same as the first embodiment. With the above-described arrangement without gaps, the magnetic field generated by the electromagnet 3 is continuous in the circumferential direction. As a result, the magnetic field H of the target 1a has a waveform with little change as shown in FIG.
Therefore, the occurrence of eddy current loss due to the change in the magnetic field H is reduced.

In each of the above embodiments, the homopolar electromagnet 3 has been described. However, the same configuration can be adopted for a heteropolar electromagnet.

[0014]

The present invention configured as described above has the following effects. According to the stator unit of the magnetic bearing of the first aspect, the bias current can be arbitrarily changed, so that the bias current is reduced according to the rotation state of the rotating body, thereby weakening the magnetic field generated by the bias current coil. Eddy current loss can be reduced.

According to the stator unit of the magnetic bearing of the present invention, since the magnetic field generated by the electromagnet is continuous without interruption in the circumferential direction, the change in the magnetic field is reduced, and the eddy current loss is reduced.

According to the control type magnetic bearing of the third aspect, the bias current can be arbitrarily changed independently of the control current, and the controller reduces the bias current when the rotation of the rotating body is stabilized. Therefore, the magnetic field generated by the bias current coil is weakened, and eddy current loss is reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a main configuration of a stator unit of a magnetic bearing according to a first embodiment of the present invention, as viewed from an axial end of a rotating body.

FIG. 2 is a block diagram illustrating a configuration of a control type magnetic bearing employing the stator unit.

FIG. 3 is a diagram showing a simplified cross section along the axial direction of a rotating body in the stator unit of the magnetic bearing according to the embodiment.

FIG. 4 is a graph showing a change in a magnetic field in the rotating body.

FIG. 5 is a plan view of a main configuration of a stator unit of a magnetic bearing according to a second embodiment, viewed from an axial end of a rotating body.

FIG. 6 is a graph showing a change in a magnetic field in the rotating body of the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotating body 2 Stator housing 3 Electromagnet 4 Control current coil 5 Bias current coil 6 Displacement sensor 7 A / D converter 8 DSP 9 D / A converter 10, 11 Amplifier 12 Rotation sensor

Claims (3)

[Claims] 1. A stator housing arranged around a rotating body, and a plurality of stator housings are circumferentially arranged to be opposed to the rotating body by being supported by the stator housing, each of which is:
A stator unit for a magnetic bearing, comprising: an electromagnet having a control current coil and a bias current coil. 2. The stator unit for a magnetic bearing according to claim 1, wherein said electromagnet has an inner end face facing said rotating body continuously arranged in a circumferential direction. 3. A magnetic bearing having a plurality of electromagnets for supporting a rotating body in a non-contact manner, each electromagnet having a control current coil and a bias current coil; and performing the control based on a displacement of the rotating body. A control device that supplies a control current and a bias current to the current coil and the bias current coil, respectively, to control the position of the rotating body, and that reduces the bias current when the rotation of the rotating body is stabilized. And control type magnetic bearing.