JPH05180224A - Magnetic bearing controlling device - Google Patents

Abstract

PURPOSE:To reduce working time of a bearing for emergency per work by shortening the speed reduction time of a motor while a magnetic bearing device can not be controlled. CONSTITUTION:When a brake signal is sent to a relay coil 23 through an OR circuit and driver 28, the contacts 24 of a relay are closed, and the current generated by a motor 5 is consumed by the brake resister 20 through the contacts 24, reducing the speed of the motor 5. When the abnormality in a magnetic bearing is detected, a magnetic bearing abnormality signal is sent to a relay coil 22 through a driver 27 and also sent to the relay coil 23 through the OR circuit 26 and driver 28, closing the relay contacts 24 and contacts 25, as a result, the current generated by the motor 5 is consumed by the brake resister 20 and a brake resister 21, rapidly reducing the speed of the motor 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing control device, and more particularly to a magnetic bearing control device for controlling an axial flow pump having rotating blades supported by magnetic bearings.

[0002]

2. Description of the Related Art FIG. 3 is a longitudinal sectional view of a conventional turbo molecular pump and a view showing a control system. In FIG. 3, a turbo molecular pump 10 includes a rotating shaft 1 and a stator 2, and detects a relative position between the rotating shaft 1 and the stator 2 so as to face the lower end side of the rotating shaft 1 and the upper and lower sides of the rotating shaft 1. Position detector 3
a, 3b, 3c are provided, and electromagnets 4a, 4b, 4 for magnetically bearing the rotary shaft 1 are provided above and below the rotary shaft 1.
c and 4d are provided. Further, a motor 5 for rotationally driving the rotary shaft 1 is provided so as to face the central portion of the rotary shaft 1. The rotation of the motor 5 is controlled by the motor controller 7, and the magnetic bearings of the electromagnets 4a to 4d are controlled by the bearing controller 6. The bearing controller 6 and the motor controller 7 are provided outside the pump body. Further, emergency bearings 11 and 12 are provided at the upper and lower ends of the rotary shaft 1. The emergency bearings 11 and 12 support the rotary shaft 1 when the magnetic bearing device becomes out of control. The bearing controller 6, the motor controller 7, and the turbo molecular pump 10 are cables 1
It is electrically connected by 3, 14, and 15.

In the above-mentioned turbo molecular pump 10, the detection signals of the position detectors 3a to 3c are given to the bearing controller 6, and the electromagnets 4a to 4d of the electromagnets 4a to 4d are arranged so that the gap between the rotating shaft 1 and the stator 2 becomes constant. Electromagnetic force is controlled,
The rotation speed of the motor 5 is controlled by the motor controller 7, and the motor 5 is controlled to decelerate when the pump is stopped. When the magnetic bearing device cannot be controlled, an abnormality of the magnetic bearing is detected, the control of the magnetic bearing is turned off, and the motor is supported in the state where the rotary shaft 1 is supported by the emergency bearings 11 and 12 in the same manner as when the pump is normally stopped. The rotating shaft 1 is decelerated by 5.

[0004]

By the way, it is preferable for the use of the turbo molecular pump 10 that the acceleration and deceleration of the rotary shaft 1 by the motor 5 be carried out rapidly with the maximum capacity of the motor 5. However, since the suction force from the motor 5 becomes a disturbance to the rotating shaft 1 and adversely affects the magnetic bearing control, the acceleration / deceleration characteristic of the motor 5, that is, the motor output is limited by the magnetic bearing performance.

On the other hand, as the emergency bearings 11 and 12 which operate when the magnetic bearing device is out of control, vacuum bearings are used which are lubricated by a solid lubricant from the environment of use. However, the vacuum bearing is inferior in durability to a bearing lubricated with oil or grease used for general industries, and thus the number of times of operation of the emergency bearings 11 and 12 is limited. Is.

Therefore, a main object of the present invention is to provide a magnetic bearing control device capable of shortening the deceleration time of the motor to reduce the operating time per emergency bearing when the magnetic bearing device cannot be controlled. That is.

[0007]

SUMMARY OF THE INVENTION The present invention includes a magnetic bearing control including a detecting means for detecting an abnormality of a magnetic bearing, the rotating shaft being supported by an emergency bearing according to the detection output of the detecting means, and the motor being decelerated. The device is configured to rapidly decelerate the motor with a motor deceleration characteristic different from that during normal motor deceleration, in response to detection of an abnormality in the magnetic bearing by the detection means.

[0008]

According to the magnetic bearing control device of the present invention, when the abnormality of the magnetic bearing is detected, the motor is rapidly decelerated with a motor deceleration characteristic different from that during normal motor deceleration, so that the emergency bearing can be operated once. The operating time of can be reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an electric circuit diagram of a motor controller according to an embodiment of the present invention. Referring to FIG. 1, a chopper circuit 71 controls the motor 5 by a chopper, and the chopper circuit 71 includes a transistor Tr.
1 to Tr6 and diodes D1 to D6, the motor 5
A control circuit 72 formed of an inverter for controlling the drive frequency of is connected. Further, the relay contact 24 and the braking resistor 20 are connected in series between the output of the chopper circuit 71 and the ground, and the relay contact 25 and the braking resistor 21 are connected between the connection point of the relay contact 24 and the braking resistor 20 and the ground. A series circuit is connected. These braking resistors 20 and 21 are provided to consume the energy generated by the motor 5 when decelerating the motor. A magnetic bearing abnormality signal is applied to the relay coil 22 via the driver 27 from the detector that detects the abnormality of the magnetic bearing, and is also applied to the relay coil 23 via the OR circuit 26 and the driver 28. A brake signal for frequency-braking the motor 5 is also given to the relay coil 23 via the OR circuit 26 and the driver 28.

FIG. 2 is a diagram showing the motor current and the spindle speed during normal deceleration and the motor current and the spindle speed during abnormal magnetic bearings. Next, the operation of the embodiment of the present invention will be described with reference to FIGS. When a brake signal for braking the motor 5 by the number of frequencies is given from the OR circuit 26 to the relay coil 23 via the driver 28,
The relay contact 24 is closed. In this state, the generated current generated by the motor 5 during frequency braking is consumed by the braking resistor 20. The deceleration characteristic of the motor 5 in this state is as shown by the solid line in FIG. Next, a magnetic bearing abnormality signal is sent from the detector for detecting abnormality of the magnetic bearing to the driver 2
Is given to the relay coil 22 via
When applied to the relay coil 23 via the R circuit 26 and the driver 28, the relay contacts 20 and 21 are closed.
In this state, the motor 5 is frequency-braked,
The generated current generated by the motor 5 is the braking resistance 20,
21 is consumed, so that the consumption rate of the generated energy is increased and the braking performance is improved as compared with the case where the braking resistor 25 is simply connected. Motor 5 in this case
The deceleration characteristic of is shown by the dotted line in FIG.

In the above embodiment, the braking resistor 20,
21 is constant regardless of the number of rotations of the motor 5, but is not limited to this, and a variable resistor or the like may be used to
The braking resistance value may be continuously changed in accordance with the number of revolutions.

[0012]

As described above, according to the present invention, when the abnormality of the magnetic bearing is detected, the motor is rapidly decelerated due to the motor deceleration characteristic different from the normal motor deceleration. It is possible to shorten the deceleration time of the motor, reduce the operating time per emergency bearing, and prolong the service life.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a motor controller according to an embodiment of the present invention.

FIG. 2 is a diagram showing a motor current and a spindle speed during normal deceleration and a motor current and a spindle speed during a magnetic bearing abnormality.

FIG. 3 is a vertical sectional view of a conventional turbo molecular pump and a diagram showing a control system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating shaft 2 stator 3a-3c position detector 4a-4d electromagnet 5 motor 7 motor controller 20,21 braking resistance 22,23 relay coil 24,25 relay contact 26 OR circuit 27,28 driver 71 chopper circuit

Claims (1)

[Claims] 1. A magnetic bearing control device including a detection means for detecting abnormality of a magnetic bearing, wherein a rotating shaft is supported by an emergency bearing according to a detection output of the detection means, and a motor is decelerated. A magnetic bearing control device characterized in that, in response to detecting an abnormality in the magnetic bearing, the motor is rapidly decelerated with a motor deceleration characteristic different from that during normal motor deceleration.