JPH01253591A - Motor for turbo-molecular pump - Google Patents

Abstract

PURPOSE:To surely and quickly stop a rotor by preventing the power feed of the charge energy stored in a smoothing capacitor to a control power circuit from being cut off until the slip of an induction motor is switched from positive to negative when the power outage is detected. CONSTITUTION:The commercial alternating current (a) is rectified by a rectifying circuit 10 and converted into the DC voltage, then it is fed to an induction motor 40 connected to a turbo-molecular pump via a DC-DC converter 20 and an inverter circuit 30. When the power outage is detected by a power outage detecting circuit 61, the charge energy of the smoothing capacitor 12 of the rectifying circuit 10 and the regenerative power of the induction motor 40 serve as a power source to feed the power from a control power circuit 65. In this case, a prohibiting circuit 62 forcibly stopping the operation of the converter 20 or the inverter circuit 30 during the period required for the slip of the induction motor 40 to be changed from positive to negative is provided. The feed of the charge energy to the control power circuit 65 is prevented from being quickly cut off.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor for a turbomolecular pump installed, for example, in a vacuum evacuation system of a semiconductor device.

Traditionally, oil diffusion pumps have been adopted as standard equipment in the vacuum pumping systems of semiconductor equipment, which are reliable and inexpensive because they do not have mechanical mechanisms. Very expensive turbo-molecular pumps are gradually being adopted in order to meet the demands of ultra-high vacuum and cleaner vacuum evacuation equipment, which are extremely demanding. The feature of this turbomolecular pump is that the rotor, which is driven by an induction motor whose primary frequency is controlled, rotates at an extremely high speed (50,000 to 70,000 rpm). Therefore, even if the power is turned off while maintaining the vacuum state, it will take a considerable amount of time for the rotor to stop. In particular, turbomolecular pump motors equipped with magnetic bearings in place of the rotor's oil lubrication mechanism can achieve a very high level of cleanliness, but the above-mentioned disadvantages become even more pronounced, causing problems in terms of worker waiting time. Of course, this also poses a problem in that the mechanical life is shortened due to vibration of the rotating mechanism at the resonance point through which the speed passes before stopping. Therefore,
A typical turbo molecular pump motor is designed to stop the rotor in a short time by switching the induction motor to a regenerative braking state.

FIG. 3 shows a simplified electrical configuration diagram of a conventional turbo molecular pump motor.

There, the input commercial alternating current a is converted into a rectifier circuit 10,
- The DC converter 20 converts the DC voltage into a DC voltage, and the inverter circuit 30 switches the resulting DC voltage to create a high-frequency current, which drives an induction motor 40 connected to a turbo molecular pump (not shown) at high speed. It has a basic configuration.

Note that a speed detector 50 is connected to the induction motor 40 to detect this rotational speed.

To explain in more detail, a power outage detection circuit 61 is connected to the input stage of the rectifier circuit 10, which detects a power outage of commercial AC a and outputs the detection result as a power outage detection signal 611. A regenerative resistor 68 that consumes regenerative power supplied from the induction motor 50 in a regenerative braking state is connected to the output stage 20 . This DC
The -DC converter 20 and the inverter circuit 30 are circuits that adjust the primary voltage and -order frequency of the induction motor 40, respectively, and are both placed under the control of the motor control circuit 30. In other words, the motor control circuit 30 controls the DC-DC converter 20 and the inverter circuit 30 so that the rotational speed of the induction motor 40 matches the rotational speed setting value of the speed setting device 63, and thereby constant speed control of the induction motor 40 is performed. It is about to be done. Moreover, when the power outage detection circuit 61 detects a power outage, the rotational speed setting value of the speed setter 63 is set to a value suitable for bringing the induction motor 40 to an emergency stop, thereby causing the induction motor 40 to enter the regenerative braking state. The structure is as follows.

By the way, the motor control circuit 66 is powered by a control power supply circuit 65 like the speed setter 63 and the speed detector 50, and the power input to the control power supply circuit 65 is extracted from the output stage of the rectifier circuit 10. Therefore, even if a power outage occurs, it is necessary to operate the motor control circuit 66 and the like before the induction motor 40 completely stops. Therefore, at the beginning of a power outage, the smoothing capacitor 12 of the rectifier circuit 10
The electric charge energy stored in the motor 40 is used as a power supply source, and the regenerative power supplied from the induction motor 40 brought into a regenerative braking state is used as a power supply source until the motor stops. There is.

However, in the case of the above conventional example, the induction motor 40 is in the rated operation state, that is, the smoothing capacitor 1
If a power outage occurs while the induction motor 2 has sufficient charge energy stored, the rotor will surely and quickly stop without any problem. However, if a power outage occurs while the induction motor 40 is running, Before the induction motor 40 switches to the regenerative braking state, most of the charge energy stored in the smoothing capacitor 12 is supplied to the induction motor 40, although insufficiently, and the power supply to the control power supply circuit 65 is interrupted. As a result, the induction motor 40, that is, the rotor, becomes free.
There is a problem that it becomes a run state. As mentioned above, this can lead to problems with worker waiting time and shortened bearing life, but especially in turbomolecular pump motors equipped with magnetic bearings, the rotor floats in the event of a power outage. Even though a fail-safe design is implemented using backup power sources such as batteries, there is still a risk that the free-running rotor may be damaged.

As a countermeasure for this inconvenience, it is conceivable to add a new battery for power outage to the control power supply circuit 65, but this increases the cost commensurately with this, so it cannot be said to be very practical.

The present invention has been devised in view of the above circumstances, and provides a motor for a turbo molecular pump that can reliably and quickly stop a rotor even if a power outage occurs at any timing by making a few changes. With the goal.

The turbo molecular pump motor according to the present invention is connected to a rectifier circuit that rectifies input commercial alternating current and converts it into a direct current voltage using a smoothing capacitor, and an input stage of the rectifier circuit. ,
A power outage detection circuit that detects a commercial AC power outage and outputs the detection result as a power outage detection signal, a DC-DC converter connected to the output stage of the rectifier circuit, and a switching system for the DC voltage derived from the DC-DC converter. An inverter circuit that supplies current to an induction motor connected to a turbo molecular pump, and a circuit that provides a rotation speed setting value for the induction motor, which is used to set the rotation speed to stop the induction motor when a power outage detection signal indicates a power outage. A speed setter that provides a value, a speed detector that detects the rotation speed of the induction motor, and voltage amplitude control of the DC-DC converter and inverter control based on the detection result of the speed detector and the rotation speed setting value of the speed setter. In order to operate the motor control circuit that controls the switching frequency of the circuit, the speed setter, the speed detector, and the motor control circuit, power is supplied from commercial AC during normal times, while at the beginning of a power outage Well,
A control power supply circuit that receives power from the charge energy stored in the smoothing capacitor, and also receives power from the regenerative power when the induction motor is in a regenerative braking state after a power outage, and a speed detection circuit. a circuit for forcibly stopping the operation of the DC-DC converter or inverter circuit for a period required for the slip of the induction motor to change from positive to negative when the signal indicates a power outage; The regenerative resistor is connected to the input side of the induction motor and consumes regenerated power from the induction motor.

When the power failure detection circuit detects a commercial AC power failure, the rotational speed setting value in the speed setting device is set to a value that brings the induction motor into a regenerative braking state, and at the same time, the DC-D
The operation of the C converter or inverter circuit is forcibly stopped by the prohibition circuit. This forced stop is maintained only for a period required for the slip of the induction motor to change from positive to negative, which is caused by the rotational speed set value being set as described above.

On the other hand, before a power outage, power is supplied to the control power supply circuit using commercial alternating current, but when a power outage is detected, power is first supplied using the charge energy stored in the smoothing capacitor. In this state, the charge energy supplied from the smoothing capacitor is blocked by the forcedly stopped DC-DC converter or inverter circuit and is not supplied to the induction motor, and the motor control circuit that controls the speed of the induction motor etc. will be the only power supply source.

And when the slip of the induction motor changes from positive to negative,
When the DC-DC converter or inverter circuit resumes operation, the induction motor enters a regenerative braking state, and the generated regenerative power is consumed by the regenerative resistor, causing the induction motor to stop rotating. .

Practical Benefits (1) Hereinafter, one embodiment of a turbo-molecular pump motor according to the present invention will be described with reference to the drawings. FIG. 1 is an electrical configuration diagram of a turbo molecular pump motor, and FIG. 2 is a timing chart of main signals, etc. for explaining the operation of the turbo molecular pump motor.

The turbo molecular pump motor shown here is a magnetically levitated type in which a rotor (not shown) is levitated by a magnetic bearing.The rotor is rotated at an ultra-high speed by a speed-controlled induction motor 40, and can be used as a vacuum pump. The configuration is such that it provides the following functions.

The power supply circuit connected to the induction motor 40 will be described in detail below.

A commercial alternating current a is introduced into this power supply circuit, and the input commercial alternating current a is converted into a direct current voltage by a rectifier circuit 10 consisting of a diode bridge 11 and a smoothing capacitor 12.

At the output stage of the rectifier circuit 10, there is a DC-DC converter 20 that converts the converted DC voltage into a higher DC voltage.
is connected to the output stage of the DC-DC converter 20, and the induction motor 40 is connected to the output stage of the DC-DC converter 20 by switching the obtained DC voltage (hereinafter referred to as inverter voltage E).
An inverter circuit 30 is connected to generate a primary current to be applied to the inverter circuit 30 . Note that a shunt resistor 67 is provided between the DC-DC converter 20 and the inverter circuit 30 to detect the magnitude of the current supplied from the DC-DC converter 20.
is connected, and the detection result is output as a voltage as a signal 671.

Connected to the input stage of the inverter circuit 30 is a regenerative resistor 68 that consumes regenerative power flowing backward through the inverter circuit 30 from the induction motor 40 in a regenerative braking state. This regenerative resistor 68 is a combination circuit including a resistor, a switching element, etc., and is designed to cause regenerative power to be consumed by the built-in resistor only when a regenerative braking signal 6612, which will be described later and which is derived from the motor control circuit 66, is active. The structure is as follows. Note that a speed detector 50 for detecting the rotational speed of the rotor, that is, the induction motor 40, is provided on the magnetic bearing of the rotor (not shown). The rotational speed data, which is the detection result of the speed detector 50, is introduced via a signal 51 to a motor control circuit 66 that controls both the DC-DC converter 20 and the inverter circuit 30.

To explain in more detail, a power outage detection circuit 61 is connected to the input stage of the rectifier circuit 10, which compares the voltage value obtained by rectifying the commercial AC a with a preset reference value, and uses the comparison result as a power outage detection signal. Speed setter 6, which will be described later as 611
3. They are each led to an inhibition circuit 62.

The speed setter 63 is a circuit that includes a variable frequency oscillator, an F/V converter, etc., and outputs the rotational speed setting value of the induction motor 40 as a voltage as a signal 631. Here, the rotational speed of the rotor can be freely varied. Since there is no need to do so, it is of a semi-fixed type, but the configuration is such that the rotation speed setting value can be varied depending on the information indicated by the power failure detection signal 611 and the signal 641 from the start/stop switch 64. . Among them, a power outage detection signal 6 that causes a power outage of commercial AC a.
11 becomes active, the speed setter 63 outputs a rotational speed setting value that brings the induction motor 40 into a braking state as a signal 631 to the motor control circuit 66. In addition to the signals 631 and 51 described above, the motor control circuit 66 also includes a power failure detection signal 6.
A reset signal 621 is introduced which is signal-processed by an inhibition circuit 62 (described later).

This prohibition circuit 62 is a circuit that latches the power failure detection signal 611 for a prohibition period T. To explain this prohibition time T, if the power failure detection signal 611 becomes active, the rotational speed setting value of the speed setting device 63 will change, but the timing of this change and the actual slip S of the induction motor 40 will change. There is a time delay between the timing of the change from positive to negative because there is a delay element in the motor control circuit 66. The prohibited time T is set between this time delay and the road. In this embodiment, the prohibition circuit 62 is a latch circuit, but the reset signal 6
Depending on the circuit configuration of the motor control circuit 66 to which the signal 21 is sent, it may be replaced with a circuit such as a delay circuit.

The motor control circuit 66 is a main circuit in a feedback control system that controls the rotational speed of the induction motor 40, and converts a signal 631 corresponding to the rotational speed setting value from the speed setting device 63 into a target value signal and F/V. The configuration is such that a signal 6651 corresponding to the rotational speed of the induction motor 40 that has passed through the converter 665 is used as a feedback signal to control the DC-DC converter 20 and the inverter circuit 30.

To explain in more detail, the deviation signal 6671 derived from the fJii calculator 667 that compares the voltages of the signal 631 and the signal 6651 is divided into a system that controls the inverter control circuit 30 and a system that controls the DC-DC converter 20. I'm here.

The former system includes a slip control signal 66 corresponding to the slip S of the induction motor 40 generated through a dead band circuit 661.
11 and a signal 665 corresponding to the induction motor 400 rotation speed.
1, and an oscillator 663 that generates two-phase oscillation according to the added voltage value of the adder 662. The oscillator 663 outputs a three-phase switching signal that causes the inverter circuit 30 to vary the switching frequency. 66
31 is output. In addition to the signal 6621, the dead band circuit 661 outputs a regenerative braking signal 6612 that indicates that the slide S of the induction motor 40 has changed to negative at a predetermined interval.

On the other hand, the latter system includes a subtracter 665 that subtracts the signal 6641 generated through the dead band circuit 664 and the signal 671 corresponding to the output current from the DC-DC converter 20.
and a current controller 666 that performs two-phase oscillation according to the subtraction result of the subtracter 665, and the current controller 666 changes the conduction angle of the DC-DC converter 20 to vary the inverter voltage E. A two-phase switching signal 6661 is output for this purpose. This current controller 666 is configured such that it does not operate while the reset signal 621 is active. In this way, a current feedback loop is provided in the system that controls the DC-DC converter 20 from the viewpoint of stability of the system.

In addition, dead band circuits 661 and 66 provided in each system
4 is based on the fact that the induction motor 40 does not electrically follow even if the signal 631, which is the target signal of the feedback system, suddenly changes.

The motor control circuit 66 described above, the power failure detection circuit 61,
Prohibition circuit 62, speed setting device 63, start/stop switch 64
, a regenerative resistor 68, a speed detector 50, etc., are controlled by a control power supply circuit 65, which will be described later, to stop the induction motor 40 not only in normal circumstances but also in the event of a power outage of the commercial AC a. Power can be supplied to each of them for a limited period of time.

This control power supply circuit 65 is a DC-D
The circuit is a combination of C converters and the like, and the power supply sources necessary to drive the circuits are introduced from two systems, one from the output stage of the rectifier circuit 10 and the other from the output stage of the DC-DC converter 20. It has become. In other words, when the commercial AC a is normal, the commercial AC a is transferred to the rectifier circuit 10.
Energy is supplied from the rectified DC voltage.On the other hand, if the commercial AC a is out of power,
The structure is such that power is supplied mainly by charge energy stored in the smoothing capacitor 12 or regenerative energy generated from the induction motor 40 during regenerative braking.

The operation of the turbo molecular pump motor configured as described above will be explained with reference to FIG. 2. In addition, the dashed-dotted line shown in the figure is a graph in the case of the conventional example.

When the start/stop switch 64 is turned on, the commercial alternating current a is turned on and at the same time, the speed setting value of the speed setting device 63 changes, so that the induction motor 40 is started. In this state, circuits such as a motor control circuit that controls the speed of the induction motor 40 are supplied with power by the commercial alternating current a like the induction motor 40.

If a power outage occurs at time t1 while the induction motor 40 reaches its rated operating state, the power outage detection circuit 6
A pulse appears in the power failure detection signal 611 of No. 1, and at the same time, the rotational speed setting value in the speed setting device 63 changes to the induction motor 40.
The value is set to perform regenerative braking. Moreover, the reset signal 621 of the inhibiting circuit 62 also rises, the two-phase oscillation of the current controller 666 is stopped, and the operation of the DC-DC converter 20 is forcibly stopped. This forced stop will be maintained until time t2 when the reset signal 621 falls. This is because the charge energy stored in the smoothing capacitor 12 is transferred to the induction motor 4 in the starting state because the DC-DC converter 20 is forcibly stopped.
This means that power is not supplied to the motor control circuit 66, etc., which needs to operate until a power outage occurs and the induction motor 40 enters the regenerative braking state. obtain.

Next, the process by which the induction motor 40 reaches the regenerative braking state will be described. When the induction motor 40 is set to a rotation speed that brings it into a regenerative braking state at time 11, this set value change is caused by the dead band circuit 661 and the oscillator 66.
3, and as a result, the slope S of the induction motor 40 changes from positive to negative. Mainly, the oscillator 663 includes an integral element in order to stabilize this system. Therefore, this signal transmission will be delayed.

Furthermore, the inhibition circuit 6
The reset signal 621 output from the DC-DC converter 20 falls, and the two-phase oscillation of the current controller 666 starts to operate, and the DC-DC converter 20 resumes operation, causing the induction motor 40 to regenerate. It becomes a braking state. This means that regenerative power is generated in the induction motor 40 that is in a free running state. The regenerated power thus generated at time t2 is transferred to the control power supply circuit 65 instead of the charge energy stored in the smoothing capacitor 12.
As long as the power supply to the control power supply circuit 65 does not become unstable, it will also be consumed by the regeneration resistor 68, but after time t2, until the induction motor 40 completely stops. This means that it can be used as a power supply source.

Therefore, in the case of this embodiment, even if a power outage occurs while the induction motor 40 reaches its rated operating state, the magnetic bearing will not be damaged (and the rotor can be stopped reliably and quickly). Moreover, it does not require major equipment changes such as installing a power outage battery, and only requires adding a small amount of electronic circuitry, so it has great advantages not only in terms of cost but also in terms of reliability. , therefore, it has great significance in promoting performance improvement of turbomolecular pumps.

Note that the turbo molecular pump motor according to the present invention is not limited to the above-mentioned embodiment, and the discharge of the charge energy stored in the smoothing capacitor is not prevented by stopping the operation of the DC-DC converter, but by stopping the operation of the DC-DC converter, for example. It is also possible to adopt a form in which the operation is stopped.

More than anything, if you use a real turbo molecular pump motor,
By simply adding a simple inhibit circuit, a power outage is detected and
The structure is such that the electric charge energy stored in the smoothing capacitor does not cut off the power supply to the control power supply circuit until the slip of the induction motor changes from positive to negative, so there is no possibility of a power outage occurring at any time. Even if this happens, the rotor can be stopped quickly and reliably.

Therefore, there is a great advantage in further promoting cost and performance of a motor for a turbomolecular pump.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of an embodiment of the turbo-molecular pump motor according to the present invention, in which FIG. 1 is an electrical configuration diagram of the turbo-molecular pump motor, and FIG. 2 is an electrical configuration diagram of the turbo-molecular pump motor. This is a timing chart of main signals, etc. for explaining the operation of the motor, and FIG. 3 is a simplified electrical configuration diagram of a conventional turbo molecular pump motor. a... Commercial AC equipment 0... Rectifier circuit 12... Smoothing capacitor 20... DC-DC converter 30... Inverter circuit 40... Induction motor 50... Speed setter 61... Power failure detection circuit 611...Power failure detection signal 62...Prohibition circuit 63...Speed setter 65...Control power supply circuit 66...Motor control circuit 68...Regeneration resistor

Claims (1)

[Claims] (1) A rectifier circuit that rectifies input commercial AC and converts it into DC voltage using a smoothing capacitor, and is connected to the input stage of the rectifier circuit, detects a power outage of the commercial AC, and uses this detection result as a power outage. A power failure detection circuit that outputs a detection signal, a DC-DC converter connected to the output stage of the rectifier circuit, and a DC voltage derived from the DC-DC converter are switched to supply current to an induction motor connected to a turbo molecular pump. an inverter circuit for supplying the inverter circuit, a circuit for providing a rotational speed setting value of the induction motor, the speed setting device providing a rotational speed setting value for stopping the induction motor when the power failure detection signal indicates a power outage; a speed detector that detects the rotational speed of the induction motor; voltage amplitude control of the DC-DC converter and switching frequency control of the inverter circuit based on the detection result of the speed detector and the rotational speed setting value of the speed setter. In order to operate the motor control circuit, the speed setter, the speed detector, and the motor control circuit, power is supplied from the commercial alternating current during normal times, while at the initial stage of a power outage, power is supplied. is a control power supply that receives power supply from the charge energy stored in the smoothing capacitor, and further receives power supply from regenerative power when the induction motor is in a regenerative braking state after a power outage occurs. circuit and
When the speed detection signal indicates a power outage, a prohibition circuit for forcibly stopping the operation of the DC-DC converter or the inverter circuit for a period required for the slip of the induction motor to change from positive to negative at this timing. and a regeneration resistor connected to an input side of the induction motor and consuming regenerated power from the induction motor.