JPH1023781A - Power unit for magnetic bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power unit for the magnetic bearing of a motor easy to operate or stop without using a battery and can perform magnetic floating until the revolution of a pump drops to the safe revolution even at power stoppage. SOLUTION: This device is constituted such that the magnetic bearing of a motor 7 whose rotary shaft is borne by a magnetic bearing is supplied with a drive current. In this case, this magnetic bearing power unit possesses a generator 5 for driving the magnetic bearing rotating with the driving force of the rotary shaft of the motor 7, a DC-DC converter 31 for converting the AC power generated by the generator 5 for driving this magnetic bearing into DC power, and a constant voltage circuit 33 for making the output of this DC-DC converter 31 into constant voltage, and this supplies a magnetic bearing driving coil 10 with the output of the constant voltage circuit 33 of this device through a magnetic bearing detecting circuit 8 and a magnetic bearing driving circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing power supply for supplying a drive current to a magnetic bearing of an electric motor in which a rotating shaft used in a turbo molecular pump or the like is supported by a magnetic bearing. .

[0002]

2. Description of the Related Art Conventionally, a turbo molecular pump or the like driven by an induction motor using a magnetic bearing requires a driving operation procedure. Before the pump is driven, a magnetic levitation of a rotating shaft is performed by a bearing unit. At the time of stop, the operation is performed so that the magnetic levitation of the bearing is continued until the rotation stops or the rotation speed of the touch-down bearing decreases to the safe rotation speed. Therefore, when turning off the power of the power supply device, the operator confirms that the pump is stopped, and then operates to turn off the power of the magnetic bearing.

[0003] In such a power supply device, if a power failure occurs due to a power failure or a human error during operation of the pump, the electromagnetic force of the magnetic bearing is suddenly lost. In order to prevent this, a battery is used to supply power from the battery at the time of a power failure, to keep the magnetic bearing floating, to decelerate the pump, and to safely stop the pump.

[0004]

However, in the above-mentioned conventional power supply device, a battery must always be provided as an emergency measure, and a charging device for naturally floating-charging the battery is required. There was a problem. In addition, the battery has a large volume and weight, occupies a considerable amount of space in the pump driving device, has a heavy device weight, and requires regular maintenance and replacement of parts. In addition, if power failures occur frequently in a short period of time, the battery cannot be charged in time and the magnetic bearing cannot float.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and eliminates the above-mentioned problems. Therefore, the operation for stopping the operation is simple without using a battery, and the rotation speed of the pump is reduced to a safe rotation speed even during a power failure. It is an object of the present invention to provide a magnetic bearing power supply device capable of performing magnetic levitation until it lowers.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a magnetic bearing power supply for supplying a drive current to a magnetic bearing of an electric motor whose rotating shaft is supported by a magnetic bearing.
A magnetic bearing driving generator driven by the driving force of the rotating shaft of the motor, a DC-DC converter for converting the generated AC power of the magnetic bearing driving generator into DC power, and a DC-DC converter; A constant-voltage circuit for converting the output to a constant voltage; a constant-voltage circuit for supplying a constant-voltage circuit to the output of the constant-voltage circuit of the magnetic-bearing power supply; It is characterized by having comprised in.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a power supply device for an induction motor using a magnetic bearing according to the present invention. In FIG. 1, reference numeral 7 denotes an induction motor whose rotating shaft is supported by magnetic bearings directly connected to, for example, rotor blades of a turbo molecular pump, and 5 is driven by the rotating shaft of the induction motor 7 (for example, the induction motor 7). (A configuration in which the rotating shaft is directly connected to the rotating shaft).

In FIG. 1, the power switch 1
When the switch 2 is turned on, commercial AC power is supplied from the AC power input terminal to the rectifier circuit 1 through the fuse 13, and AC is converted to DC at the output side and output. Further, the DC output is smoothed by the smoothing capacitor 4 to become a DC voltage with little ripple.

The smoothed DC voltage is supplied to a three-phase inverter circuit 2 composed of transistors Q1, Q2, Q3, Q4, Q5 and Q6, and in accordance with a control pulse signal from the inverter control circuit 6. A three-phase AC is generated at the output of the three-phase inverter circuit 2, and the three-phase AC is applied to the three-phase induction motor 7. As a result, the three-phase induction motor 7 generates a rotating magnetic field corresponding to the frequency of the control signal of the inverter control circuit 6 and rotates. The inverter control method is preferably a PWM (pulse width modulation) method or the like which is hardly affected by the fluctuation of the DC voltage applied to the smoothing capacitor 4.

A pulse generator 14 is directly connected to the three-phase induction motor 7, and a pulse corresponding to the rotation speed of the three-phase induction motor 7 is generated. The pulse signal is converted by a pulse signal conversion circuit 15 into an analog signal. And input to the inverter control circuit 6. The inverter control circuit 6 controls the frequency so that the number of revolutions of the three-phase induction motor 7 becomes equal to the set number of revolutions in comparison with the output signal of the preset setting circuit 32.

The magnetic bearing of the present system is a magnetic levitation bearing that utilizes the power of the magnetic bearing driving generator 5 connected to the three-phase induction motor 7, so that the power of the magnetic bearing driving generator 5 cannot be used at startup. , The three-phase induction motor 7 is supported by a touchdown bearing (not shown) and starts rotating.

When the generator 5 for driving the magnetic bearing reaches a certain number of revolutions, it generates enough power for the magnetic bearing to operate sufficiently, and this power is supplied via terminals A and B to the DC-DC converter.
The magnetic bearing power supply device 3 includes a motor 31, a setting circuit 32, and a constant voltage circuit 33. As soon as the generated power is supplied from the magnetic bearing drive generator 5 to the DC-DC converter 31 of the magnetic bearing power supply 3, a constant voltage is immediately supplied from the constant voltage circuit 33 to the magnetic bearing detection circuit 8 and the magnetic bearing drive circuit 9. , And an exciting current is supplied from the magnetic bearing drive circuit 9 to the magnetic bearing drive coil 10, and the rotor of the three-phase induction motor 7 immediately magnetically levitates.

The magnetic bearing detection circuit 8 detects the magnetic levitation of the rotor of the three-phase induction motor 7 by the magnetic bearing detection coil 11, and amplifies the detection signal. The magnetic bearing drive circuit 9 supplies a current proportional to the detection signal amplified by the magnetic bearing detection circuit 8 to the magnetic bearing drive coil 10, and magnetically levitates the rotating shaft to an appropriate position.

When the three-phase induction motor 7 is stopped, the power is turned off when the power switch 12 is opened, and the rotational driving torque of the three-phase induction motor 7 is lost and the number of rotations is reduced. The generator 5 continues to rotate and continues to generate power. This generated power is DC-
It is supplied to the magnetic bearing detection circuit 8 and the magnetic bearing drive circuit 9 via the DC converter 31 and the constant voltage circuit 33,
The magnetic bearing continues the magnetic levitation operation. Since the power generated by the magnetic bearing drive generator 5 is consumed by the magnetic bearing power supply 3, the three-phase induction motor 7 is braked and the rotation speed is reduced faster than in the free run.

When the three-phase induction motor 7 is braked and decelerated, the voltage generated by the generator 5 for driving the magnetic bearing naturally drops. Until the number decreases, the rotation shaft is set so as to supply sufficient electric power for magnetic levitation.

At the time of rated rotation of the three-phase induction motor 7, since the input voltage of the constant voltage circuit 33 is high, a voltage dividing circuit (not shown) is provided and the voltage is reduced and input. When the number of rotations decreases to a certain value, an internal switch (not shown) is switched to operate so as to keep the voltage of the constant voltage circuit 33 constant.

With the above configuration, the generator 5 for driving the magnetic bearings
Is supplied to the magnetic bearing power supply device 3, and the stabilized DC voltage is supplied to the magnetic bearing detection circuit 8 and the magnetic bearing drive circuit 9 to continue the magnetic levitation of the bearing. Even when the pump is stopped, the magnetic bearing power supply device 3 supplies power stably to the magnetic bearing drive circuit 9 until the rotation speed of the pump decreases to the safe rotation speed. It does not matter. Therefore, normal operation of starting and stopping can be easily performed only by the power switch 12.

In the power supply device having the above configuration, the magnetic bearing driving generator 5, the magnetic bearing unit having the magnetic bearing driving coil 10, the magnetic bearing detecting circuit 8, and the magnetic bearing driving circuit 9 are formed as independent units. A power supply device that is compact, easy to use, and requires no maintenance can be provided.

In the above-described embodiment, the three-phase induction motor 7 has been described as an example in which the rotating shaft is supported by magnetic bearings, and the motor is not limited to the three-phase induction motor. Naturally, any electric motor may be used as long as the electric machine 5 can be driven by the driving force of the rotating shaft of the electric motor. In the above example, the three-phase induction motor 7 and the rotating shaft of the magnetic bearing driving generator 5 are directly connected. However, the magnetic bearing driving generator 5 is driven by the driving force of the rotating shaft of the three-phase induction motor 7. Any configuration may be used.

In the above embodiment, an example in which the three-phase induction motor 7 is driven by the output of the three-phase inverter circuit 2 controlled by the inverter control circuit 6 has been described. It is needless to say that the motor is not limited to the motor, and the motor may not be driven by the output of the inverter circuit.

[0021]

As described above, according to the present invention, the following excellent effects are expected. (1) Since the power supplied to the magnetic bearing drive coil of the bearing power supply device is the power generated by the magnetic bearing drive generator driven by the driving force of the rotating shaft of the motor, the operation for normally stopping the pump operation is easily performed. Can be performed, and even if power failures occur frequently in a short time, there is no problem.

(2) A battery and a charger, which were conventionally required, become unnecessary, and a magnetic bearing drive generator, a magnetic bearing unit having a magnetic bearing drive coil, a magnetic bearing detection circuit, and a magnetic bearing drive circuit are independent. By providing a unit, a great deal of merit can be expected, such as being compact and easy to use, and requiring no maintenance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a magnetic bearing power supply device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectifier circuit 2 Three-phase inverter circuit 3 Magnetic bearing power supply unit 4 Smoothing capacitor 5 Magnetic bearing drive generator 6 Inverter control circuit 7 Three-phase induction motor 8 Magnetic bearing detection circuit 9 Magnetic bearing drive circuit 10 Magnetic bearing drive Coil 11 Magnetic bearing detection coil 12 Power switch 13 Fuse 14 Pulse generator 15 Pulse signal conversion circuit 31 DC-DC converter 32 Setting circuit 33 Constant voltage circuit

Claims (1)

[Claims] 1. A magnetic bearing power supply device for supplying a drive current to a magnetic bearing of a motor whose rotating shaft is supported by a magnetic bearing, comprising: a magnetic bearing driving generator driven by a driving force of the rotating shaft of the motor; A DC-DC converter for converting AC power generated by the generator for driving the magnetic bearing into DC power;
A bearing power supply device having a constant voltage circuit for converting the output of the C converter to a constant voltage is provided, and the output of the constant voltage circuit of the bearing power supply device is driven by a magnetic bearing detection circuit and a magnetic bearing drive circuit via a magnetic bearing drive circuit. A magnetic bearing power supply device characterized in that it is configured to supply to a coil.