JP3114091B2 - Magnetic bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device, and more particularly to separating and extracting conical mode resonance and parallel mode resonance, and stabilizing an overhang rotor by controlling a radial electromagnet adapted to each resonance. The present invention relates to a magnetic bearing device.

[0002]

2. Description of the Related Art FIG. 4 shows a conceptual configuration diagram of a conventional magnetic bearing device. The magnetic bearing device is incorporated in, for example, a turbo-molecular pump. In FIG. 4, a radial electromagnet 3 and a radial position sensor 5 are disposed above the center of gravity G of the overhang rotor 1. Overhang rotor
1 is, in fact, the central axis and the umbrella section
Composed of multiple rotating blades arranged around a rotating shaft
However, in FIG. 4, for simplicity, only the rotating shaft portion is rod-shaped.
It is represented by abstraction. The overhang rotor 1
Regarding, "Overhang low with gyro effect
Schedule H∞ control of motor and magnetic bearing system ”
Proceedings of the Japan Society of Mechanical Engineers (C) Vol. 63, No. 610 (1997-6)
Familiar with. Radial electromagnet 3 and radial position sensor 5
Are paired in the X and Y directions, respectively. On the other hand, a radial electromagnet 7 and a radial position sensor 9 are disposed below the center of gravity G. Similarly, the radial direction electromagnet 7 and the radial direction position sensor 9 are also paired in the X direction and the Y direction. Here, any arrangement relationship between the radial electromagnet 3 and the radial position sensor 5 may be apart from the center of gravity G. The same applies to the arrangement relationship between the radial direction electromagnet 7 and the radial direction position sensor 9.

Since the overhang rotor 1 is accelerated while levitating in the air, when passing over a resonance point inherent in the turbo-molecular pump, the vicinity of the center of gravity G (not always coincident with the position of the center of gravity). As the center, both the upper runout and the lower runout make conical movement, and the protective bearing 1
The phenomenon of contact with 1 may occur. As a result, the bearings are consumed and vibrations are temporarily generated. As shown in FIG. 5, such a resonance point has a property of varying according to the rotation speed of the overhang rotor 1, but is generally separated into two-directional motion according to the rotation speed with the stationary state being the same starting point. That is, there are a backward movement (precession) opposite to the rotation direction and a forward movement (nutation) in the same direction as the rotation direction. here,
The conical mode resonance points exist at two points: a point where precession resonance overlaps with the rotation speed of the overhang rotor 1 and a point where nutation resonance overlaps with the rotation number of the overhang rotor 1. Further, apart from the resonance in the conical mode, the magnetic bearing device sometimes causes the resonance in the parallel mode due to the translational motion of the overhang rotor 1. The parallel mode resonance may also cause contact with the protective bearing 11 or temporary vibration. In reality, conical mode resonance and parallel mode resonance are often mixed in a complicated manner. Conventionally, the band of the compensator (the frequency band in which the phase must be stabilized by advancing the phase) is widened so as to include the resonance point of the conical mode and the resonance point of the parallel mode. (For example, by advancing the phase from 5 Hz to 300 Hz). The control during this time is shown in FIG.
It will be described based on. The radial position sensor 5 detects the upper radial position, and the radial position sensor 9 detects the lower radial position. The mode separator 12 performs coordinate conversion based on the upper radial position and the lower radial position to calculate the magnitude and phase of resonance in the conical mode and the magnitude and phase of resonance in the parallel mode.
The conical mode resonance signal is output from the conical mode compensator 1.
4 is compensated to suppress conical mode resonance. FIG. 6 shows a gain diagram of the conical mode compensator. The conical mode compensator 14 compensates for a wide band. For this reason, in a high frequency range of several hundred hertz, there is a possibility of exciting the resonance of the structure, and a notch filter is provided.
The parallel mode resonance signal is input to the parallel mode compensator 16 and compensated to suppress parallel mode resonance. Thereafter, the two compensated signals are subjected to coordinate inverse transformation in the mode combiner 18. The compensation signal for the parallel mode and the compensation signal for the conical mode are combined and sent to the upper electromagnet amplifier 20 and the lower electromagnet amplifier 22, respectively. Upper electromagnet amplifier 20 and lower electromagnet amplifier 2
2, the voltage / current is converted and sent to the radial electromagnet 3 and the radial electromagnet 7 . The radial electromagnet 3 controls the upper radial position, while the radial electromagnet 7 controls the lower radial position. That is, the radial electromagnet 3 and the radial electromagnet 7 control all resonance modes.

[0004]

By the way, the maximum value I of the control current supplied to the radial electromagnets 3 and 7 at the time of rated rotation.
_max is given by _Equation 1.

[0005]

(Equation 1) V _d is the power supply voltage, f is the rotational speed, L ₀ is the inductance of the wound windings radially electromagnet. Where I
_{If the value of max} is small, the current may saturate when error feedback is applied, and control may not be possible. For this reason,
In fact it defines the L ₀ as to become a compromise can I _max. Therefore, L ₀ must be reduced.

Next, the attraction force F generated by the radial electromagnets 3 and 7 is given by equation (2).

[0007]

(Equation 2) N is the number of turns of the winding wound around the radial electromagnet, μ ₀ is the permeability of the core of the radial electromagnet, A is the effective area of the core of the radial electromagnet, and I ₀ is the winding wound around the radial electromagnet. The equilibrium current supplied to the line, δ _0, is the gap. According to Equation 2, if N or I ₀ is increased, the generated suction force F can be increased. However, since I _max is more restricted than _Equation 1, I ₀ is also restricted. Therefore, although it is desired to increase N, L ₀
Is represented as in Equation 3.

[0008]

(Equation 3) L _L is a loss parameter. For this reason, if N is increased, L ₀ is increased and contradicts Equation 1. Eventually, the rigidity of the bearing is reduced due to the constraint of Equation 1 (the resonance frequency in the parallel mode is, for example, about 80 Hz). For this reason, there is a possibility that the device is weakened to external vibration or disturbance. In addition, as shown in FIG. 6, the high-frequency gain of the compensator becomes high, which may excite the resonance of the structure. Therefore, it is necessary to take measures such as using a notch filter. The present invention has been made in view of such conventional problems, and separates and extracts conical mode resonance and parallel mode resonance, and stabilizes the overhang rotor by controlling a radial electromagnet adapted to each resonance. It is an object to provide a magnetic bearing device.

[0009]

SUMMARY OF THE INVENTION To this end, the present invention provides a first radial position sensor disposed above the center of gravity of an overhang rotor for detecting radial runout above the overhang rotor; A second radial position sensor disposed on the side of the overhang rotor for detecting a radial runout below the overhang rotor; and a radial runout detected by the second radial position sensor and the first radial position. Based on the radial run-out detected by the sensor, the resonance of the forward motion of the conical mode inherent to the overhang rotor, conical mode
A mode separation unit that separates and extracts the resonance of the backward motion and the resonance of the parallel mode, a high-frequency compensator that compensates the high-frequency characteristics based on the resonance of the forward motion of the conical mode separated and extracted by the mode separation unit, A high-frequency amplifier for converting the output of the high-frequency compensator into a voltage / current, and a first radial direction improved in response at a high frequency for controlling the radial position based on the current output from the high-frequency amplifier An electromagnet, a low-frequency compensator for compensating for low-frequency characteristics based on resonance of backward movement and parallel-mode resonance of the conical mode separated and extracted by the mode separation unit, and a voltage / A low-frequency amplifier for current conversion; and a second radial electromagnet having increased rigidity at a low frequency for controlling a radial position based on a current output from the low-frequency amplifier. It was constructed Te. The first radial position sensor is disposed above the center of gravity of the overhang rotor, and detects a radial deflection above the overhang rotor. On the other hand, the second radial position sensor is disposed below the center of gravity of the overhang rotor, and detects a radial runout below the overhang rotor. Each of the detected signals is input to the mode separation unit. The mode separation unit calculates the resonance of the forward motion of the conical mode , which is the vibration inherent in the overhang rotor, and the conical mode.
The resonance of the backward motion and the resonance of the parallel mode are separated and extracted. The resonance signal of the forward motion in the conical mode is subjected to voltage / current conversion after compensating for the high frequency characteristics, and controls the first radial electromagnet. Further, the resonance signal of the backward motion of the conical mode and the resonance signal of the parallel mode are subjected to voltage / current conversion after compensating for the low frequency characteristics, and control the second radial electromagnet. Therefore, control of the radial electromagnet adapted to each resonance becomes possible. Since the gain of the high-frequency compensator can be kept low, resonance of the structure can be prevented. Further, the rigidity of the bearing at low frequencies can be increased. Therefore, the overhang rotor can be stabilized.

The present invention also provides a first radial position sensor disposed above the center of gravity of the overhang rotor and detecting a radial runout above the overhang rotor, and an overhang disposed below the center of gravity. A second radial position sensor for detecting a radial runout on the lower side of the rotor; a radial runout detected by the second radial position sensor; and a radial direction detected by the first radial position sensor shake overhang rotor-specific forward movement resonance of the conical mode based on the a mode separator unit for separating extract a resonance co <br/> vibration and the parallel mode of reverse movement of the conical mode, it is separated and extracted by the mode separator unit A high-frequency compensator for compensating high-frequency characteristics based on resonance of a forward motion in a conical mode; An amplifying unit, a first radial electromagnet having improved responsiveness at a high frequency for controlling a radial position based on a current output from the high frequency amplifying unit, and a conical mode separated and extracted by the mode separating unit. A first low-frequency compensator that compensates for low-frequency characteristics based on the resonance of the backward movement, a first low-frequency amplifier that converts the output of the first low-frequency compensator into a voltage / current, A third radial electromagnet which suppresses resonance of backward movement of the conical mode at a low frequency for controlling a radial position based on a current outputted from the first low frequency amplifying unit, and is separated by the mode separating unit; A second low-frequency compensator for compensating for low-frequency characteristics based on the extracted parallel-mode resonance, and a second low-frequency amplifier for converting the output of the second low-frequency compensator into a voltage / current signal And the second low-frequency amplifier A fourth radial electromagnet having increased rigidity at a low frequency for controlling the radial position based on the current output from the motor, and the fourth radial electromagnet was disposed at the position of the center of gravity. The low-frequency compensator, the low-frequency amplifier, and the radial electromagnet are separated into those corresponding to the conical mode resonance and the parallel mode resonance, respectively. Then, a fourth radial electromagnet corresponding to the resonance in the parallel mode is disposed at the position of the center of gravity. As a result, the fourth radial electromagnet for supporting the overhang rotor when the magnetic bearing device is leveled at a low frequency and the third radial electromagnet for suppressing conical movement can be separated in terms of function. Control with good stability can be performed.

Here, the arrangement positions of the first radial electromagnet, the second radial electromagnet, and the third radial electromagnet are as follows:
As long as it satisfies the function of suppressing conical movement, it can be at any position upward and downward with respect to the center of gravity,
The second radial electromagnet is disposed near the center of gravity of the overhang rotor, and the first radial electromagnet is disposed on the opposite side of the center of gravity from the second radial electromagnet or the third radial electromagnet. You can do it. The second radial electromagnet is desirably disposed at the same position as the center of gravity in consideration of supporting the overhang rotor when the magnetic bearing device is horizontal. However, in consideration of the fact that it also has a function of suppressing conical motion that occurs simultaneously in the low frequency region, it is arranged at a position close to the center of gravity. On the other hand, it is desirable that the first radial electromagnet is separated from the center of gravity by a predetermined distance in order to suppress conical movement in a high frequency region. Therefore, any of the first radial electromagnet, the second radial electromagnet, or the third radial electromagnet can be disposed above the center of gravity. If the first radial electromagnet is disposed on the opposite side of the center of gravity from the second radial electromagnet or the third radial electromagnet, the magnetic bearing device can be configured in substantially the same space as in the related art. In addition, a method of increasing the control power supply voltage in order to improve the responsiveness of the radial electromagnet at a high frequency, and a method of increasing an effective area in order to improve the rigidity at a low frequency are also possible. The number of turns of the coil of the first radial electromagnet is greater than the number of turns of the coil of the second radial electromagnet.
Small Kusuru it is also possible. The number of turns of the coil of the first radial electromagnet is determined by the number of turns of the coil of the second radial electromagnet.
Ri small By Kusuru, responsiveness of the inductance becomes small high-frequency coil of the first radial electromagnet is improved. Further, the number of turns of the coil of the second radial electromagnet is set to the first number .
By having more than the number of turns of the radial electromagnet coil ,
The inductance of the coil of the second radial electromagnet increases, and the rigidity can be improved. Thus, a stable operation of the overhang rotor can be ensured with a simple configuration in which the number of turns of the coil is devised.

Further, according to the present invention, the low-frequency compensator, the first low-frequency compensator and the second low-frequency compensator advance the phase around 0 to one hundred and several tens of hertz, and The compensator advances the phase around one hundred and several tens hertz to several hundred hertz. When applying a magnetic bearing device to a turbo molecular pump,
It is preferable that the control be divided into two controls for low frequency and high frequency around one hundred and several tens of hertz. By separating the signal into two, a high-frequency gain can be suppressed, a notch filter or the like becomes unnecessary, and a compensator with a small order can be realized.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall conceptual diagram of the first embodiment of the present invention. The radial position sensor 5 detects a radial run-out above the center of gravity of the overhang rotor 1, and corresponds to a first radial position sensor. Also,
The radial position sensor 9 detects a radial runout below the center of gravity of the overhang rotor 1, and corresponds to a second radial position sensor. The mode separation section 42 separates and extracts a conical mode resonance signal and a parallel mode resonance signal, which are vibrations unique to the overhang rotor 1. The high-frequency compensator 44 includes the mode separation unit 4
The high frequency characteristics are compensated based on the resonance signal of the forward movement of the conical mode separated and extracted in step 2. The high-frequency amplifier 50 converts the signal output from the high-frequency compensator 44 into voltage / current. The radial electromagnet 33 controls the upper radial position of the overhang rotor 1 based on the voltage / current converted signal. The low-frequency compensator 46 compensates for low-frequency characteristics based on the resonance signal of the backward movement of the conical mode and the resonance signal of the parallel mode separated and extracted by the mode separation unit 42. The low-frequency amplifier 48 converts the signal output from the low-frequency compensator 46 into voltage / current. The radial electromagnet 37 controls the lower radial position of the overhang rotor 1 based on the voltage / current converted signal.

Next, a control method according to the first embodiment of the present invention will be described. In FIG. 1, the radial position sensor 5
And the radial position sensor 9 detect the upper radial position and the lower radial position of the overhang rotor 1, respectively. The detected signal is subjected to coordinate conversion by the mode separation unit 42, and is separated and extracted into a conical mode resonance signal and a parallel mode resonance signal. The resonance signal of the forward movement in the conical mode is compensated for the high frequency characteristics by the high frequency compensator 44. The gain diagram of the compensator has the characteristic indicated by (a) in FIG. That is, since the phase advances only in the high-frequency portion, it is possible to suppress the resonance of the conical mode at the high frequency. Further, since the phase is advanced from around one hundred and several tens of hertz, a notch filter in a high frequency region is not required. Further, since the stable control of the overhang rotor 1 can be performed with the gain lowered, resonance of the structure can be prevented. The output signal of the high-frequency compensator 44 is subjected to voltage / current conversion by the high-frequency amplifier 50 and then controls the radial electromagnet 33. The radial electromagnet 33 is desirably disposed at a distance from the center of gravity G in order to suppress resonance in a conical mode around the center of gravity G. It is also desirable to reduce the number of turns in order to reduce inductance, suppress saturation of the control current, and facilitate control at high frequencies.

On the other hand, the resonance signal of the backward movement of the conical mode and the resonance signal of the parallel mode are added by the mode separation section 42 and sent to the low frequency compensator 46. The low-frequency compensator 46 compensates for the low-frequency characteristic based on the resonance signal of the backward motion of the conical mode and the resonance signal of the parallel mode. The gain diagram of the compensator has the characteristic shown by (b) in FIG. That is, since the phase advances only in the low frequency part,
It is possible to suppress the resonance of the backward motion of the conical mode and the resonance of the parallel mode at a low frequency. The output signal of the low frequency compensator 46 is supplied to a low frequency
After the current conversion, the radial electromagnet 37 is controlled. The radial electromagnet 37 is desirably disposed away from the center of gravity G in consideration of conical mode resonance, but is desirably disposed near the center of gravity G in consideration of parallel mode resonance. Accordingly, the radial electromagnet 37 is disposed immediately below the center of gravity G. This is advantageous for horizontal levitation. However, the disposition positions of the radial electromagnet 33 and the radial electromagnet 37 are either above or below the center of gravity G, considering that the purpose is to suppress the resonance in the conical mode and the resonance in the parallel mode. May be. In addition, if the space is not considered, or if the radial electromagnet can be configured in a small space, the radial electromagnet 33 and the radial electromagnet 37 may be disposed only in one of the upper and lower directions. .

Next, FIG. 3 shows an overall conceptual diagram of a second embodiment of the present invention. The same elements as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The mode separation unit 52
A conical mode resonance signal and a parallel mode resonance signal, which are vibrations unique to the overhang rotor 1, are separated and extracted. The low-frequency compensator 56 compensates for the low-frequency characteristic based on the resonance signal of the backward movement of the conical mode separated and extracted by the mode separation unit 52. The low-frequency amplifier 60 converts the signal output from the low-frequency compensator 56 into voltage / current. The radial electromagnet 47 controls the lower radial position of the overhang rotor 1 based on the voltage / current converted signal. Further, the low frequency compensator 58 compensates for the low frequency characteristic based on the parallel mode resonance signal separated and extracted by the mode separation unit 52. The low-frequency amplifier 64 converts the signal output from the low-frequency compensator 58 into voltage / current. Radial electromagnet 49
Controls the radial position of the center of gravity of the overhang rotor 1 based on the voltage / current converted signal.

Next, a control method according to a second embodiment of the present invention will be described. When FIG. 3 is compared with FIG. 1, which is the first embodiment of the present invention, the following differences are made in terms of functions. That is,
The resonance of the backward motion of the conical mode and the resonance of the parallel mode at low frequency are controlled separately and independently. For this reason, the low frequency compensator 56 and the low frequency amplifier 6
A low-frequency compensator 58, a low-frequency amplifier 64, and a radial electromagnet 49 are provided as controls for parallel mode resonance. The gain diagrams of the low-frequency compensator 56 and the low-frequency compensator 58 have the characteristics shown in FIG. That is, since the phase advances only in the low frequency portion, it is possible to suppress the resonance in the conical mode and the resonance in the parallel mode at the low frequency. The radial electromagnet 49 is used for the overhang rotor 1.
It is arranged at the position of the center of gravity G to improve the rigidity while maintaining the balance. In order to control the radial electromagnet 49 in a low frequency range, the number of turns can be increased. The parallel mode resonance is compensated by the low frequency compensator 58. The radial electromagnet 47 is desirably disposed away from the position of the center of gravity G for the purpose of preventing resonance in the conical mode. Electromagnet for low frequency is replaced with radial electromagnet 4
7 and the radial electromagnet 49 are separated and independent, so that the stability of the control system is further improved.

[0018]

As described above, according to the present invention, the resonance of the conical mode and the resonance of the parallel mode are separated by the mode separation section, and the resonance of the forward motion of the conical mode at a high frequency is compensated by the high-frequency compensator. Since the parallel mode resonance and the conical mode backward motion resonance at the low frequency are configured to be compensated by the low frequency compensator, it is possible to control the radial electromagnet adapted to each resonance. Also,
Since the gain of the high-frequency compensator can be kept low, resonance of the structure can be prevented. Further, the rigidity of the bearing at low frequencies can be increased. Therefore, stable control of the overhang rotor can be achieved.

Further, according to the present invention, the parallel mode resonance and the conical mode backward motion resonance at low frequencies are each compensated by the independent low frequency compensator, so that rigidity is well balanced at low frequencies. , The cone motion can be suppressed efficiently, and more stable control can be performed.

Further, according to the present invention, the arrangement of the first radial electromagnet, the second radial electromagnet, and the third radial electromagnet is devised, thereby improving the rigidity and preventing the resonance in the conical mode. I can do it. Further, the magnetic bearing device can be configured in substantially the same space as that of the related art.

Furthermore, according to the present invention, the responsiveness at high frequencies can be improved and the rigidity can be improved by devising the number of turns of the coil of the first radial electromagnet and the number of turns of the coil of the second radial electromagnet. Can be improved. Therefore, stable operation of the overhang rotor can be ensured.

Further, according to the present invention, since the control is divided into two controls for low frequency and high frequency around one hundred and several tens of hertz, the gain of high frequency can be suppressed, and a notch filter or the like becomes unnecessary. , A compensator with a small order can be realized.

[0023]

[Brief description of the drawings]

FIG. 1 is an overall conceptual diagram of a first embodiment of the present invention.

FIG. 2 is a gain diagram of a compensator.

FIG. 3 is an overall conceptual diagram of a second embodiment of the present invention.

FIG. 4 is a conceptual configuration diagram of a conventional magnetic bearing device.

FIG. 5 is a diagram showing resonance characteristics of a conical mode and a parallel mode.

FIG. 6 is a gain diagram of a conventional compensator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Overhang rotor 3, 7, 33, 37, 47, 49 Radial electromagnet 5, 9, Radial position sensor 11 Protective bearing 42, 52 Mode separation part 44 High frequency compensator 50 High frequency amplifier 46, 56, 58 Low frequency Compensator 48, 60, 64 Low frequency amplifier

Claims (5)

(57) [Claims] A first radial position sensor disposed above the center of gravity of the overhang rotor for detecting a radial run-out above the overhang rotor; and a lower position sensor disposed below the center of gravity and located below the overhang rotor. A second radial position sensor for detecting a radial runout of the second radial position sensor, based on a radial runout detected by the second radial position sensor and a radial runout detected by the first radial position sensor. Of the forward motion of the conical mode inherent to the overhang rotor
A mode separation unit that separates and extracts resonance , resonance of backward motion of conical mode, and resonance of parallel mode, and a high-frequency compensator that compensates high-frequency characteristics based on resonance of forward motion of conical mode separated and extracted by the mode separation unit When,
A high-frequency amplifier for converting the output of the high-frequency compensator into a voltage / current, and a first radius having improved responsiveness at a high frequency for controlling a radial position based on the current output from the high-frequency amplifier. A directional electromagnet, a low-frequency compensator for compensating for low-frequency characteristics based on the resonance of the backward motion and the parallel-mode resonance of the conical mode separated and extracted by the mode separation unit, and a voltage output from the low-frequency compensator. / A low-frequency amplifier for current conversion, and a second radial electromagnet having increased rigidity at a low frequency for controlling the radial position based on the current output from the low-frequency amplifier. Magnetic bearing device. 2. A first radial position sensor disposed above the center of gravity of the overhang rotor for detecting radial runout above the overhang rotor, and a lower side of the overhang rotor disposed below the center of gravity. A second radial position sensor for detecting a radial runout of the second radial position sensor, based on a radial runout detected by the second radial position sensor and a radial runout detected by the first radial position sensor. Of the forward motion of the conical mode inherent to the overhang rotor
A mode separation unit that separates and extracts resonance , resonance of backward motion of conical mode, and resonance of parallel mode, and a high-frequency compensator that compensates high-frequency characteristics based on resonance of forward motion of conical mode separated and extracted by the mode separation unit When,
A high-frequency amplifier for converting the output of the high-frequency compensator into a voltage / current, and a first radius having improved responsiveness at a high frequency for controlling a radial position based on the current output from the high-frequency amplifier. A directional electromagnet; a first low-frequency compensator for compensating low-frequency characteristics based on resonance of backward movement of the conical mode separated and extracted by the mode separation unit;
A low-frequency amplifier for converting the output of the low-frequency compensator into a voltage / current, and a low-frequency amplifier for controlling the radial position based on the current output from the first low-frequency amplifier. A third radial electromagnet for suppressing the resonance of the backward movement of the conical mode, and a second for compensating the low-frequency characteristics based on the resonance of the parallel mode separated and extracted by the mode separation unit.
A low-frequency compensator, a second low-frequency amplifier for converting the output of the second low-frequency compensator into a voltage / current, and a current output from the second low-frequency amplifier. A magnetic bearing device, comprising: a fourth radial electromagnet whose rigidity is increased at a low frequency for controlling a radial position based on the fourth radial electromagnet, wherein the fourth radial electromagnet is disposed at the position of the center of gravity. 3. The second radial electromagnet is disposed near a center of gravity of an overhang rotor, and the first radial electromagnet is opposite to the second radial electromagnet or the third radial electromagnet across the center of gravity. The magnetic bearing device according to claim 1, wherein the magnetic bearing device is disposed on a side of the magnetic bearing device. 4. The number of turns of the coil of the first radial electromagnet is smaller than the number of turns of the coil of the second radial electromagnet.
Roast magnetic bearing device according to claim 1, 2 or 3, wherein the. 5. The low-frequency compensator, the first low-frequency compensator, and the second low-frequency compensator advance the phase around 0 to one hundred and several tens of Hertz, and the high-frequency compensator has a hundred 5. The magnetic bearing device according to claim 1, wherein the phase is advanced around ten to several hundred hertz.