JPH06280874A - Feeder of magnetic bearing device - Google Patents

Abstract

PURPOSE:To continue operation of a magnetic bearing device until the rotational frequency of a rotor is lowered enough in a device for continuing operation of a magnetic bearing device by utilizing the regenerative power of a motor at the time of service interruption. CONSTITUTION:When feeding to a motor driver 71 is stopped due to service interruption or the like, regenerative power is generated by coils 61U, 61V, 61W with rotation of a rotor of a DC brushless motor. When the rotational frequency of a rotor is high, a switch circuit 88 is off-state so that regenerative voltage is rectified and smoothed by diodes 86a-86f and condensers 83, 84 according to the ordinary rectifying system and supplied to a magnetic bearing control circuit 77. When the rotational frequency of the rotor is lowered, a voltage doubler rectifier command signal 93 is output from a regenerative voltage lowering detecting circuit 90 and the switch circuit 88 is turned on and change-over to the voltage doubler rectifier system takes place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for supplying power to a magnetic bearing device which magnetically levitates a rotor such as a turbo molecular pump and holds the rotor at a predetermined position.

[0002]

2. Description of the Related Art In a turbo molecular pump capable of obtaining an ultrahigh vacuum, a non-contact type magnetic bearing device is used as a rotor bearing and a mechanical bearing is used for protection, but it is If the power supply to the magnetic bearing device is stopped due to a power failure, etc., in order to prevent wear and damage to the rotor and the protective bearing, the rotor must be replaced with the protective bearing after the rotor speed has decreased sufficiently. Need to make contact. Therefore, conventionally, a backup battery is provided, and in the event of a power failure, power is supplied from the backup battery to the magnetic bearing device to continue operation.

However, since the battery requires maintenance and has a low reliability,
Recently, as disclosed in, for example, Japanese Patent Laid-Open No. 59-23098, a motor that rotates a rotor is used as a generator during a power failure, and regenerative power of this motor is supplied to a magnetic bearing device during a power failure. To eliminate the need for a backup battery, or special features 1
As disclosed in Japanese Unexamined Patent Publication No. 47110, it has been proposed to reduce the battery capacity by supplying regenerative electric power of the motor to the battery during a power failure.

[0004]

However, when the regenerative electric power of the motor is used at the time of power failure as described above, the voltage regenerated from the motor at the time of power failure is substantially proportional to the rotational speed of the rotor, so that the rotational speed decreases. The degree of decrease in the power generation voltage at is decreased below the voltage required for the operation of the magnetic bearing before the mechanical bearing can withstand the low speed. Therefore, it becomes difficult for the magnetic bearing device to operate using the regenerative electric power of the motor.

Therefore, there is a problem that the rotor is lowered onto the protective bearing at a relatively high rotational speed, the rotor and the protective bearing are worn, and the life of these tends to be shortened. The present invention has been made in view of such a problem, and in a device that continues the operation of the magnetic bearing device by utilizing the regenerative power of the motor at the time of power failure, the operation of the magnetic bearing device until the rotation speed of the rotor is sufficiently reduced. It is an object of the present invention to provide a power supply device for a magnetic bearing device, which is capable of continuing.

[0006]

According to a first aspect of the present invention, there is provided a magnetic bearing device for a magnetic bearing device, comprising: a magnetic bearing device which magnetically levitates and holds a rotor which is rotationally driven by a motor acting as a generator when power feeding is stopped. It is used to convert the AC voltage generated from the motor when the power supply is stopped to a DC voltage and supply it to the magnetic bearing device, and the rectification method is a normal rectification method or a double voltage rectification method according to the predetermined operation limit value of the magnetic bearing. A rectifier circuit that can be switched to a different system, and a switching unit that switches the rectification system of the rectifier circuit.

According to a second aspect of the present invention, there is provided a power supply device for a magnetic bearing device, wherein the switching means according to the first aspect of the invention determines that the voltage generated from the motor is below a predetermined value when the power supply to the motor is stopped. It detects and switches the rectification method of the rectification circuit from the normal rectification method to the voltage doubler rectification method.

According to a third aspect of the present invention, there is provided a magnetic bearing device power supply device, wherein the switching means in the first aspect of the invention detects that the number of rotations of the motor has become a predetermined value or less when power supply to the motor is stopped. Then, the rectification method of the rectification circuit is switched from the normal rectification method to the voltage doubler rectification method.

According to a fourth aspect of the present invention, there is provided a magnetic bearing device power supply device in which the switching means in the first aspect of the invention is configured so that the current generated from the motor becomes a predetermined value or more when the power supply to the motor is stopped. It detects and switches the rectification method of the rectification circuit from the normal rectification method to the voltage doubler rectification method.

[0010]

In the power feeding device of the magnetic bearing device of the present invention, when the power feeding to the motor is stopped, the AC voltage generated from the motor is converted into the DC voltage by the rectifying circuit and the DC voltage is supplied to the magnetic bearing device. Here, the rectifying circuit can switch between a normal rectifying system and a double voltage rectifying system according to a predetermined operation limit value of the magnetic bearing, and the rectifying system is switched by the switching means. The switching means changes the rectification method of the rectification circuit from the normal rectification method to a voltage doubler when the voltage generated from the motor becomes less than a predetermined value or when the rotation speed of the motor becomes less than a predetermined value. Switch to rectification method. As a result, it becomes possible to continue the operation of the magnetic bearing device until the rotational speed of the rotor is sufficiently reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a power feeding device for a magnetic bearing device of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows an overall configuration of a turbo molecular pump device to which this embodiment is applied.

The turbo-molecular pump device 1 is installed in, for example, a semiconductor manufacturing device, and discharges process gas from a chamber or the like. In this example, a flange 11 is formed on the upper end of the outer casing 10 formed in a cylindrical shape, and is connected to the semiconductor manufacturing apparatus by a bolt or the like.

A plurality of stator blades 12 are provided inside the outer casing 10.
Are arranged, and a plurality of rotor blades 14 are arranged between the respective stator blades 12. The rotor blades 14 are provided on the outer peripheral wall of the rotor 15, and the rotor 15 is fixed to the rotor shaft 18 with bolts 19 so as to rotate in conjunction with the rotor shaft 18 made of a magnetic material.

The rotor 15 uses a so-called magnetic bearing, and two pairs of radial electromagnets 20 are arranged above the rotor shaft 18 so as to face each other with the rotor shaft 18 interposed therebetween. They are arranged so as to be orthogonal to each other. Adjacent to the radial electromagnet 20, the rotor shaft 18
Two pairs of radial sensors 22 are provided so as to face each other across the pair.

Similarly, two pairs of radial electromagnets 24 are arranged under the rotor shaft 18, and the radial electromagnets 24 are also provided with two pairs of radial sensors 26 adjacent to each other. By supplying an exciting current to the radial electromagnets 20 and 24, the rotor shaft 18 is magnetically levitated in the radial direction. This exciting current is controlled in response to the position detection signals from the radial direction sensors 22 and 26 during magnetic levitation, whereby the rotor shaft 18 is held at a predetermined radial position.

A DC brushless motor 30 is arranged between the radial direction sensor 22 and the radial direction sensor 26 inside the outer casing 10. When the DC brushless motor 30 is energized, the rotor shaft 18 and the
The rotor blades 14 fixed to this are adapted to rotate.

A disc-shaped metal disk 31 made of a magnetic material is fixed to the lower portion of the rotor shaft 18, and a pair of axial electromagnets 32 and 34 are arranged so as to sandwich the metal disk 31 and face each other. Has been done. Further, an axial sensor 36 is arranged so as to face the cut end of the rotor shaft 18.

The exciting currents of the axial electromagnets 32 and 34 are controlled in accordance with the position detection signal from the axial sensor 36, so that the rotor shaft 18 is levitated and held at a predetermined axial position. There is. Also, this rotor shaft 1
A rotation sensor 38 for detecting the number of rotations of the rotor shaft 18 is arranged at the lower end of the rotor 8.

An exhaust port 52 for exhausting a process gas or the like from the semiconductor manufacturing apparatus is arranged in the lower portion of the exterior body 10 of the turbo molecular pump device. Further, a temperature sensor 50 such as a thermistor is arranged near the exhaust port 52. Further, the turbo molecular pump device is connected to the controller 45 via the connector 44 and a cable.

FIG. 2 is a block diagram showing the electrical construction of essential parts of the turbo molecular pump device 1 and the controller 45.
As shown in this figure, the turbo molecular pump device 1 includes a DC brushless motor 30 as a motor that acts as a generator when power supply is stopped, and an electromagnet 6 that constitutes a magnetic bearing device.
2 (radial electromagnets 20 and 24 and axial electromagnet 3
Represent 2,34. ) And a position sensor 63 (representing the radial sensors 22, 26 and the axial sensor 36).

The controller 45 also includes a motor driver 71 for driving the DC brushless motor 30, a switching amplifier 72 for supplying an exciting current to the electromagnet 62,
A servo controller 73 that controls the switching amplifier 72 based on the output signal of the position sensor 63 to hold the rotor shaft 18 at a predetermined position, a microcomputer 74 that controls the turbo molecular pump device as a whole, and an AC power from an AC power supply. A power supply circuit 75 that rectifies the voltage to generate a DC voltage to supply power to the motor driver 71, a DC voltage from the power supply circuit 75 is stabilized, and a switching amplifier 72, a servo controller 73, and a microcomputer 74.
And a switching regulator 76 that supplies power to the. Switching amplifier 72 and servo controller 73
Constitute a magnetic bearing control circuit 77. Note that the power supply device 75 may also be provided with a switching regulator.

FIG. 3 is a circuit diagram showing the configurations of the power supply circuit 75 and the motor driver 71 in FIG. The power supply circuit 75 includes a rectifier 82 that rectifies the AC voltage from the AC power supply 81, and two smoothing capacitors 83 and 84 that are provided in series between the output terminals of the rectifier 82.

The motor driver 71 includes six transistors 85a to 85f provided between output terminals of the rectifier 82.
And six diodes 86a-86f.
Transistors 85a, 85b, Transistors 85c, 8
5d and transistors 85e and 85f are respectively connected in series and provided between the output terminals of the rectifier 82.
In addition, the diodes 86a, 86b, the diode 86c,
86d and diodes 86e and 86f are also connected in series and provided between the output ends of the rectifier 82.

The pair of transistors 85a and 85b, the pair of transistors 85c and 85d, the pair of transistors 85e and 85f, and the diodes 86a and 86.
The pair of b, the pair of diodes 86c and 86d, and the pair of diodes 86e and 86f are connected in parallel, respectively.

Each of the diodes 86a to 86f has a cathode on the positive electrode side of the rectifier 75. Connection points of transistors 85a and 85b and diodes 86a and 86
The connection point of b is connected to one end of the U-phase winding 61U of the DC brushless motor 30 via the motor cable 87. The connection point of the transistors 85c and 85d and the connection point of the diodes 86c and 86d are connected to one end of the V-phase winding 61V of the DC brushless motor 30 via the motor cable 87. The connection point of the transistors 85e and 85f and the connection point of the diodes 86e and 86f are the motor cable 8
W-phase winding 61W of the DC brushless motor 30 via
Is connected to one end of the switch circuit 88 as switching means. Switch circuit 8
The other end of 8 is connected to the connection point of capacitors 83 and 84. The U-phase winding 61U, the V-phase winding 61V, and the W-phase winding 61W are star-connected. Each transistor 85
The motor drivers of a to 85f are controlled to be turned on and off by the microcomputer 74 to drive the DC brushless motor 30. Diode 86a
˜86f and capacitors 83 and 84 form a rectifier circuit that rectifies the regenerated voltage.

Further, in this embodiment, there is provided a regenerative voltage drop detection circuit 90 and an AND gate 91 which are composed of a comparator having hysteresis. One input end of the regenerative voltage drop detection circuit 90 is connected to the positive side of the rectifier 82, and a predetermined reference value 92 is input to the other input end. The regenerative voltage drop detection circuit 90 outputs a voltage doubler rectification command signal 93 when the regenerative voltage from the windings 61U, 61V, 61W of the DC brushless motor 30 becomes a reference value 92 or less. Regenerative voltage drop detection circuit 90
The output of is input to one input terminal of the AND gate 91,
A regenerative power generation command signal 94 from a sequence circuit (not shown) is input to the other input terminal of the AND gate 91. Further, the ON / OFF of the switch circuit 88 is controlled by the output signal of the AND gate 91.

Next, the operation of this embodiment will be described.
In normal times, power is supplied from the power supply circuit 75 to the motor driver 71, and the motor driver 71 drives the DC brushless motor 30. Further, power is supplied from the power supply circuit 75 and the switching regulator 76 to the magnetic bearing control circuit 77, and the rotor is magnetically levitated.

When power supply to the motor driver 71 is stopped due to a power failure or the like, a regenerative power generation command signal 94 is output from a sequence circuit (not shown). Further, as the rotor of the DC brushless motor 30 rotates, the windings 61U, 61V,
A regenerative voltage is generated from 61W. When the number of rotations of the rotor is high, the regenerative voltage drop detection circuit 90 does not output the voltage doubler rectification command signal 93, so the switch circuit 88 is in the OFF state, and the diodes 86a to 86f and the capacitors 83 and 84 cause normal switching. The regenerated voltage is rectified and smoothed by the rectification method, and the magnetic bearing control circuit 77 is supplied with power to continue the operation of the magnetic bearing device.

4A to 4C respectively show the winding 61.
The voltage generated in U and 61V, the voltage generated in windings 61V and 61W, and the voltage generated in windings 61U and 61W are shown. In the case of the normal rectification method, the voltage across both ends of the capacitors 83, 84, that is, the voltage between AB in FIG. 3 is as shown in FIG. 4 (d). The broken line indicates the smoothed DC voltage.

After that, when the number of rotations of the rotor decreases, the regenerative voltage decreases, and the voltage becomes necessary to increase it,
Double voltage rectification command signal 93 from regenerative voltage drop detection circuit 90
Is output, the output of the AND gate 91 becomes high, and the switch circuit 88 is turned on. This switches to the voltage doubler rectification method. At this time, the voltage across the capacitor 83 is as shown in FIG. 4 (e), and the voltage across the capacitor 84 is as shown in FIG. 4 (f).
The voltage between both ends of 84, that is, the voltage between AB in FIG. 3 is shown in FIG.
As shown in, it becomes twice as much as that at the time of normal rectification.

As described above, according to this embodiment, the operation of the magnetic bearing device can be continued until the rotational speed of the rotor is sufficiently reduced. Therefore, after the rotor is braked, the rotor is touched down to the protective dry bearing. Also, the wear of the rotor and the bearing can be reduced, and the service life can be extended.

Further, the impact at the time of touchdown is reduced, and the device using the pump is less likely to be adversely affected. Instead of the regenerative voltage drop detection circuit 90 in FIG. 3, as shown in FIG. 5, the rotation sensor 3 in FIG.
An F / V conversion circuit 97 for inputting a pulse 96 for each rotation from 8 for frequency-voltage conversion (F / V conversion);
A rotation speed reduction detection circuit 95 that compares the output voltage of the / V conversion circuit 97 with a reference value 92 that is set in advance corresponding to the rotation speed at which the regenerative voltage becomes a predetermined value or less may be provided. In this rotation speed decrease detection circuit 95, the rotation speed of the rotor is the reference value 9
When the number of rotations drops below 2 corresponding to 2, the double voltage rectification command signal 93 is output.

Further, in the configuration of FIG. 3, the duty of the regenerative current flowing through the diodes 86a to 86f in the voltage doubler rectification method is about 1/3 of that in the normal rectification method, so that the peak current value becomes high. If the motor cable 87 is long, the voltage drop due to the resistance of the cable is about three times that of the conventional one, and the actual voltage drops.
As a countermeasure, as shown in FIG.
The 86f and the capacitors 83 and 84 may be arranged in the immediate vicinity of the motor.

In the above embodiment, an example in which there is no backup battery is shown, but the present invention can also be applied to a device that has a battery and supplies the regenerative voltage of the motor to the battery during a power failure.

[0035]

As described above, according to the first to third aspects of the invention, the AC voltage generated from the motor when the power supply to the motor is stopped is rectified and supplied to the magnetic bearing device, and the operation of the magnetic bearing is performed. A predetermined limit value, for example, when the voltage generated from the motor is below a predetermined value, or when the rotation speed of the motor is below a predetermined value, or the current generated from the motor is above a predetermined value. At this time, the rectification method can be switched from the normal rectification method to the voltage doubler rectification method, and there is an effect that it is possible to continue the operation of the magnetic bearing device until the rotational speed of the rotor is sufficiently reduced. The life of the touchdown bearing can be extended and the battery can be downsized.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a turbo molecular pump device to which an embodiment of the present invention is applied.

FIG. 2 is a block diagram showing an electrical configuration of main parts of a turbo molecular pump device and a controller in FIG.

3 is a circuit diagram showing a configuration of a power supply device and a motor driver in FIG.

FIG. 4 is a waveform diagram for explaining the operation of the circuit of FIG.

5 is a block diagram showing a modified example of the circuit of FIG.

FIG. 6 is a circuit diagram showing another modification of the circuit of FIG.

[Explanation of symbols]

 15 rotor 18 rotor shaft 30 DC brushless motor 71 motor driver 77 magnetic bearing control circuit 83, 84 capacitors 86a to 86f diode 88 switch circuit 90 regenerative voltage drop detection circuit

Claims (4)

[Claims] 1. A magnetic bearing device for magnetically levitating and holding a rotor that is rotationally driven by a motor acting as a generator when power supply is stopped, and converts AC voltage generated from the motor when power supply is stopped into DC voltage. Rectifier circuit that can be switched between a normal rectifying method and a double voltage rectifying method while supplying the rectifying method to the magnetic bearing device, and the rectifying method of this rectifying circuit is switched according to the predetermined operating limit value of the magnetic bearing. A power feeding device for a magnetic bearing device, comprising: a switching unit. 2. The switching means detects, when power supply to the motor is stopped, that the voltage generated from the motor has become a predetermined value or less, and doubles the rectification method of the rectification circuit from the normal rectification method. The power supply device for a magnetic bearing device according to claim 1, wherein the power supply device is switched to a voltage rectification system. 3. The rectifying method of the rectifying circuit is changed from a normal rectifying method to a double voltage rectifying method by detecting that the number of rotations of the motor has become a predetermined value or less when power supply to the motor is stopped. The power feeding device for a magnetic bearing device according to claim 1, wherein the method is switched to a system. 4. The switching means detects, when power supply to the motor is stopped, that the current generated from the motor has exceeded a predetermined value, and doubles the rectification method of the rectification circuit from the normal rectification method. The power supply device for a magnetic bearing device according to claim 1, wherein the power supply device is switched to a voltage rectification system.