JPH0919177A - Controller for motor - Google Patents

Abstract

PURPOSE: To prolong the lives of the touch down bearings of a motor by supplying desired power to magnetic bearing means over a comparatively long time, until the number of revolution of the rotor lowers sufficiently at the stopping time of the motor, and making it possible to noncontact-support the rotor by the magnetic bearing means. CONSTITUTION: The number of revolution of a high-frequency motor 6 having a rotor part 6a provided in a rotor 2 noncontact-supported by magnetic bearing parts 3, 4, 5 and a stator part 6b arranged around it is controlled with an inverter 17, on the basis of a detected number-of-revolution signal from a number-of- revolution sensor 8 for detecting the number-of-revolution of the rotor 2. At the stopping tipe of the motor 6, kinetic energy which the rotor 2 has is converted into power by a converter 18, and the output power of the converter 18 is supplied to a magnetic bearing control circuit 12 and is supplied to the motor 6 through the inverter 17. The frequency of a driving signal outputted by the inverter 17 to the motor 6 so as to make the electric energy of the converter 18 approximately constant, when the motor 6 stops, is gradually made lower than the detected number-of-revolution signal from the number-of- revolution sensor 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device,
More specifically, the present invention relates to a control device for a high-frequency electric motor for driving a rotating body which is supported in a non-contact manner by magnetic bearing means in, for example, a magnetic bearing type vacuum pump.

[0002]

2. Description of the Related Art In a magnetic bearing type vacuum pump, a rotating body which is supported in a non-contact manner by magnetic bearing means is driven to rotate at a high speed by a high frequency electric motor. The electric motor includes a rotor portion provided on the rotating body and a stator portion provided around the rotor portion. Around the rotating body, an electromagnet and a position sensor that form the magnetic bearing means, a rotation speed sensor that detects the number of rotations of the rotating body, and when there is no support by the magnetic bearing means such as during a power failure or when the rotating body is stopped. A touchdown bearing or the like for supporting the rotating body is provided. The electric motor control device includes an inverter for driving the electric motor and controlling the number of revolutions thereof, and a converter for supplying electric power generated by regenerative braking when the electric motor is stopped to the magnetic bearing means and the inverter.
The inverter outputs a drive signal to the stator portion of the electric motor, and controls the frequency of the drive signal based on the rotation speed detection signal from the rotation speed sensor, thereby controlling the rotation speed of the electric motor. Then, when the electric motor is stopped, the inverter controls the frequency of the drive signal to the electric motor based on the rotation speed detection signal from the rotation speed sensor so that the slip amount of the electric motor becomes constant, thereby performing regenerative braking. It is designed to let you. In this specification, the amount of slip means the difference between the actual rotation speed of the rotor of the electric motor and the frequency of the drive signal of the inverter.

When power supply to the electric motor is stopped due to a power failure or the like, the rotating body continues to rotate while slightly decelerating. Meanwhile, the converter converts the rotational kinetic energy of the rotating body into electric power and supplies the electric power to the magnetic bearing means and the inverter. Then, the magnetic bearing means continues the non-contact support of the rotating body by the electric power supplied from the converter. On the other hand, the inverter controls the frequency of the drive signal so that the slip amount becomes constant by the electric power supplied from the converter, continues the regenerative braking, and gradually decelerates the electric motor. When the rotating body is decelerated to some extent and its kinetic energy is reduced, the electric power supplied from the converter to the magnetic bearing means and the inverter is also reduced. When the magnetic bearing means cannot contactlessly support the rotating body by the electric power supplied from the converter, the rotating body is supported by the touchdown bearing, further decelerates, and then stops.

[0004]

The conventional motor control device described above has the following problems because the regenerative braking is performed with a constant slip amount when the motor is stopped.
That is, when the slip amount is constant, as shown in the graph of FIG. 3, the power generation amount is large in a state where the rotation speed of the rotating body is high immediately after the power supply is stopped, and when the rotation speed decreases, the power generation amount significantly decreases. The electric power supplied to the magnetic bearing means at a relatively high rotation speed becomes very small, and the rotating body cannot be supported by the magnetic bearing means in a non-contact manner. Therefore, the rotating body is received by the touchdown bearing at a relatively high rotation speed and touches down, which causes a problem that the life of the touchdown bearing is shortened. In order to avoid this, it is necessary to provide auxiliary power means such as a battery and operate the magnetic bearing means by the auxiliary power means until the rotation speed of the rotating body is sufficiently reduced. The problem of being troublesome arises.

The object of the present invention is to solve the above problems,
Provided is a control device for an electric motor, which is capable of supplying a desired electric power to a magnetic bearing means for a relatively long time until the rotational speed of the rotating body is sufficiently reduced when the electric motor is stopped so that the magnetic bearing means can support the rotating body in a non-contact manner. Especially.

[0006]

A control device for an electric motor according to the present invention is a high frequency electric motor having a rotor portion provided on a rotating body which is supported by a magnetic bearing means in a non-contact manner and a stator portion arranged around the rotor portion. Is controlled by an inverter based on a rotation speed detection signal from a rotation speed sensor that detects the rotation speed of the rotating body, and when the electric motor is stopped, the kinetic energy of the rotating body is converted into electric power by the converting means. In the controller of the electric motor which converts the electric power to the magnetic bearing means and supplies the output electric power of the converting means to the electric motor through the inverter, the converting means converts the electric power to the magnetic bearing means when the electric motor stops. Of the drive signal output to the electric motor so that the output electric power of the It is characterized in that Kusuru.

[0007]

When the electric motor is stopped, as shown in FIG. 2, the inverter reduces the slip amount when the rotational speed of the rotating body is high immediately after the stop of energization and reduces the slippage as the rotational speed of the rotating body decreases. By gradually increasing the amount, the frequency of the drive signal to the electric motor is controlled so that the output power amount of the conversion means becomes substantially constant. Therefore, a constant amount of power generation is obtained for a relatively long time until the rotation speed of the rotating body becomes sufficiently low, and this is supplied to the magnetic bearing means so that the rotating body does not operate at the sufficiently low rotation speed by the magnetic bearing means. Contact supported.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows a main part of a magnetic bearing type vacuum pump.

The vacuum pump comprises a casing (1) and a shaft-shaped rotating body (2) vertically arranged inside the casing (1). The rotating body (2) is contactlessly supported by the axial magnetic bearing portion (3) provided in the casing (1) and the upper and lower radial magnetic bearing portions (4) and (5), and the built-in high-frequency motor
(6) allows high speed rotation. Electric motor (6) is a rotating body
The rotor part (6a) provided in (2) and the stator part (6b) provided in the casing (1) around the rotor part (6a) are provided, and the stator part (6b) serves as the motor control device (7). It is connected.
Also, a rotation speed sensor (8) for detecting the rotation speed of the rotating body (2).
Is provided in the casing (1), and a rotation speed detection signal from this is input to the motor control device (7). Rotating body (2) with magnetic bearings (3), (4), and (5) at two locations above and below the casing (1)
Touchdown bearings (10) (11) are provided to receive the rotating body (2) when the support of the bearing is lost. The touchdown bearings (10) and (11) are, for example, angular contact ball bearings.

The axial magnetic bearing portion (3) is composed of a rotating body (2).
For supporting the axial direction (vertical direction) of the rotating body (2), and a pair of annular electromagnets (axial electromagnets) arranged so as to sandwich the flange portion (2a) in the middle of the rotating body (2) from both upper and lower sides. (3a) is provided. The upper and lower axial electromagnets (3a) attract the flange portion (2a) of the rotating body (2) by magnetic force to support the rotating body (2) in the axial direction in a non-contact manner.The magnetic bearing control circuit (12) It is connected to the. The casing (1) is provided with an axial position sensor (13) for detecting the position of the rotating body (2) in the axial direction. The sensor (13) is connected to the rotating body position detection circuit (14). The radial magnetic bearings (4) (5)
It is for supporting (2) in the radial direction (horizontal direction). The upper radial magnetic bearing (4) is
Is provided with four electromagnets (radial electromagnets) (4a) arranged so as to be sandwiched from two sides in the radial direction orthogonal to each other. The lower radial magnetic bearing portion (5) also includes four similar radial electromagnets (5a). The radial electromagnets (4a) and (5a) are for attracting the rotating body (2) by magnetic force and supporting it in the radial direction in a non-contact manner, and are connected to the magnetic bearing control circuit (12) described above. Two pairs of radial position sensors (15) are provided near the upper radial magnetic bearing portion (4) for detecting two positions in the upper radial direction of the rotating body (2) which are orthogonal to each other in the radial direction. Two pairs of radial position sensors (16) are provided near the lower radial magnetic bearing section (5) for detecting two positions in the lower radial direction of the rotating body (2) which are orthogonal to each other. . These radial position sensors (15) (16) are connected to the above-mentioned rotary member position detection circuit (14). Magnetic bearings (3) (4) (5)
, Position sensor (13) (15) (16), rotating body position detection circuit (14)
The magnetic bearing control circuit (12) constitutes magnetic bearing means for supporting the rotating body (2) in a non-contact manner.

The rotating body position detection circuit (14) detects the position of the rotating body (2) in the axial direction based on the output of the axial position sensor (13), and the upper and lower radial position sensors (15) (16). It is for detecting the position of the rotating body (2) in the radial direction based on the output of. Magnetic bearing control circuit (12), based on the output of the rotor position detection circuit (14),
The axial electromagnet (3a) and the radial electromagnets (4a) (5a) are controlled so that the position of the rotating body (2) becomes a predetermined target position.

The electric motor control device (7) comprises an inverter (17) and a converter (conversion means) (18). The rotation speed detection signal that is the output of the rotation speed sensor (8) is
7) and the inverter (17) controls the frequency of the drive signal to the electric motor (6) so that the output electric energy of the converter (18) becomes almost constant when the electric motor (6) is stopped.
It is designed to be gradually lower than the rotation speed detection signal from (8). Others are the same as in the case of the conventional example.

When the power supply to the electric motor (6) is stopped due to a power failure or the like, the rotor (2) is supported by the magnetic bearings (3), (4) and (5) in a non-contact manner as in the case of the conventional example. With the
Continue to rotate while gradually decelerating. When the electric power supplied from the converter (18) to the magnetic bearing control circuit (12) becomes very small and the magnetic bearings (3), (4) and (5) stop working, the rotating body (2 ) Is the touchdown bearing (10) (11)
Supported by and will eventually stop. In this case, the inverter (1
As shown in Fig. 2, 7) shows that when the rotation speed of the rotating body (2) is high immediately after the power supply is stopped, the slip amount is reduced and the rotating body (2)
By gradually increasing the amount of slippage as the rotation speed decreases, the frequency of the drive signal to the electric motor (6) is controlled so that the output power amount of the converter (18) becomes substantially constant. Therefore, a constant amount of power generation is obtained for a relatively long time until the rotation speed of the rotating body (2) becomes sufficiently low, and the rotating body (2) keeps the magnetic bearing parts (3) (4) at a sufficiently low rotation speed. ) (5) Non-contact supported. And since the rotating body (2) touches down after the rotating speed of the rotating body (2) becomes sufficiently low,
The life of the touchdown bearings (10) (11) is extended and damage to the pump can be prevented.

[0015]

According to the motor control device of the present invention,
As described above, when the electric motor is stopped, a desired electric power is supplied to the magnetic bearing means for a relatively long time until the rotation speed of the rotor is sufficiently reduced, and the rotor is supported by the magnetic bearing means in a non-contact manner. You can Therefore, when the rotating body is received by the touchdown bearing, the rotation speed of the rotating body is sufficiently small, and the life of the touchdown bearing is extended.
Since the magnetic bearing means can be operated by the electric power supplied from the converting means until the rotational speed of the rotating body becomes sufficiently small, it is not necessary to provide an auxiliary electric power means such as a battery, and maintenance for that is unnecessary. Is.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a main part of a magnetic bearing type vacuum pump showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the number of rotations of a rotating body, the amount of slip, and the amount of power generation in the controller for the electric motor of the embodiment of FIG.

FIG. 3 is a graph showing the relationship between the number of rotations of a rotating body and the amount of slippage and the amount of power generation in a conventional motor control device.

[Explanation of symbols]

 (2) Rotating body (3) Axial magnetic bearing (4) (5) Radial magnetic bearing (6) High frequency motor (6a) Rotor (6b) Stator (7) Motor controller (8) Rotation speed sensor ( 10) (11) Touchdown bearing (12) Magnetic bearing control circuit (13) Axial position sensor (14) Rotating body position detection circuit (15) (16) Radial position sensor (17) Inverter (18) Converter (Conversion means)

Claims (1)

[Claims] 1. The number of revolutions of a high frequency electric motor having a rotor portion provided on a rotor which is supported by a magnetic bearing means in a non-contact manner and a stator portion provided around the rotor, and the number of revolutions of the rotor is detected. Based on the rotation speed detection signal from the rotation speed sensor, when the motor is stopped, the kinetic energy of the rotating body is converted into electric power by the converting means, and the output power of the converting means is converted to the magnetic field. In a controller for an electric motor that supplies the electric power to the bearing means and supplies the electric power to the electric motor through the inverter, the inverter controls the output electric power of the conversion means to be substantially constant when the electric motor stops. A control device for an electric motor, wherein a frequency of a drive signal output to the electric motor is gradually made lower than a rotational speed detection signal from the rotational speed sensor.