JPH0242196A - Power unit for turbo molecular pump - Google Patents

Abstract

PURPOSE:To prevent the discharge of a battery to the utmost by providing the battery and a regenerative power extracting mans utilizing the rotation of a rotor as an auxiliary power source for a magnetic bearing with an electromagnet supporting the rotor and preferentially using the regenerative power when a main power source is stopped. CONSTITUTION:A rotor R is supported in the noncontact state by the magnetic force generated by the excitation to an electromagnet MG of a magnetic bearing in a turbo molecular pump, the rotor R is rotated by a high-frequency motor M at a high speed. In this case, a battery 5 and a regenerative power extracting means 12 utilizing the rotation of the rotor R are provided in addition to a main power source 31 such as a commercial power source as a power unit. When the main power source 31 is stopped, a switch S1 is closed by a power outage detecting circuit 43, the battery voltage Vb is applied to a terminal (b), the regenerative voltage Va is applied to a terminal (a). If Va>Vb, the regenerative power is fed to the load by the excitation of a diode D1, on the other hand if Va<Vb, the battery power is fed to the load by the excitation of a diode D2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply device applied to a turbo-molecular pump employing a magnetic bearing.

[Prior Art] A magnetic bearing uses magnetic force to levitate a rotor from a fixed member on the base side and supports the rotor in a non-contact manner. These magnetic bearings have no mechanical friction or sliding parts, and are completely oil-free.
This type of TMP is gradually becoming established as a very promising one. In particular, those that use electromagnets can vary the magnetic force through a control circuit and actively finely adjust the bearing clearance, so most active types are used in TMPs. ing.

By the way, this type of bearing needs to be kept energized at all times, so if there is a power outage, there is a risk of so-called touchdown (hereinafter abbreviated as T or D) failure, where the rotor comes into solid contact with the fixed member on the base side. There is. To prevent this situation, TMPs are usually equipped with T and D bearings.

However, since this bearing is a dry type that does not use oil, it lacks durability. Therefore, conventionally, in order to keep the magnetic bearing functioning until the rotor comes to a complete stop in the event of a power outage, many machines switch the power source to a battery to continue magnetic levitation.

[Problem to be Solved by the Invention] However, the capacity of a battery is not infinite, and in normal use, a battery that has been charged over a day will normally be completely discharged in less than an hour. therefore,
If a power outage continues for a long time or occurs repeatedly, the battery is likely to become insufficiently charged, and in this case, the magnetic bearing will not be driven sufficiently, putting a heavy burden on the T and D bearings, leading to damage to the T and D. Gender comes out.

Therefore, in the past, in the event of a power outage, either regenerative braking or DC braking was applied to the rotor rotation so that the TMP could be stopped before the battery was completely discharged. There are things that exist. Regenerative braking involves performing negative slip control on a motor to use the motor as a generator, and braking the motor using the negative torque generated at this time. Further, direct current braking is a method in which direct current is applied to the motor to periodically brake the rotation of the rotor.

However, regenerative braking has the problem that the braking force is weak in the low speed range of the rotor, and it takes a long time to come to a complete stop. On the other hand, DC braking has the problem of requiring current to be supplied from the battery, which causes the battery to discharge faster, and also because it lacks braking power in high-speed ranges, it takes a long time to come to a stop.

As described above, it is difficult to stop the TMP quickly in the past, and in the event of a power outage, there is a high possibility that the battery will continue to discharge and the rotor will have to rely on the T and D bearings to support the rotor.

However, in order to prevent T and D damage, it is desirable to keep the magnetic bearing functioning for a certain amount of time.

The present invention has been made with attention to such problems, and an object of the present invention is to realize a TMP power supply device that can effectively supply power to a magnetic bearing during a power outage until the rotor completely stops. It is an object.

[Means for Solving Problem X1] In order to achieve the above object, the present invention employs the following configuration.

That is, the fMP power supply device according to the present invention is applied to a turbo molecular pump that includes an electromagnet that applies magnetic force to a rotor, and an electromagnet control circuit that drives this electromagnet to function as a magnetic bearing. The electromagnet control circuit is capable of supplying power to the electromagnet control circuit, and includes, in addition to the main power source, at least a battery and regenerative power extraction means that can extract regenerative power using rotation of the rotor.
When the main power supply is stopped, if the regenerative voltage is equal to or higher than a reference value, it is applied to the electromagnet control circuit, and if the regenerative voltage is less than the reference value, the battery voltage is applied to the electromagnet control circuit. It is characterized by its composition.

[Function] With this kind of configuration, the magnetic bearing can be driven by regenerative power until the rotor's rotation speed drops to a constant speed, so the battery can not supply power after the rotor's low speed range. It will be done. This makes it possible to reduce dependence on the battery during a power outage and extend the bearing driving time, compared to the conventional system in which power is supplied from the dead battery.

[Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the TMP to which this embodiment is applied includes a high-frequency motor M for driving a rotor R, and an electromagnet MG for applying magnetic force to the motor M.
The motor M is controlled by the motor control circuit 1 of this power supply device.
Further, the electromagnets MG are each driven and controlled by an electromagnet control circuit 2 of this power supply device.

The power supply device uses, for example, a commercial frequency AC power source as the main power source 31, and after once rectifying it through a rectifier 32, it is directly supplied to the motor control circuit 1, and after being stepped down by a DC/DC converter 33, it is supplied to the electromagnet control circuit. Power is supplied to each circuit 2.

The motor control circuit 1 directly inputs count pulses proportional to the rotor rotation speed N from a pulse oscillator PG attached to the high-frequency motor M, and also inputs a detection signal from the rotation detection circuit 41. , positive or negative slip control can be performed depending on the rotor rotational speed N. For this purpose, the motor control circuit 1 has at least D
It has a built-in C/DC converter and an inverter, and is configured to shift the step-down ratio of the former and the modulation ratio of the latter in stages.

In addition, in the electromagnet control circuit 2, a small gap in the magnetic bearing is detected from a displacement sensor DET attached to the electromagnet MG, and this detection signal is amplified to determine the magnitude of the current to be applied to the electromagnet MG. I'm trying to control it.

The operations of these control circuits 1.2 are mainly performed by a sequence control section 11 built into the motor control circuit 1. In the sequence control unit 11, when the start switch SW1 is turned on, positive slip control is started to start up TMP, and when a stop command is input, it is switched to negative slip control and TMP is started.
Add braking to. Stop command is issued by stop switch SW2
It is emitted either during operation, during a power outage, or when an abnormality occurs. The apparatus is provided with a power failure detection circuit 43 and an abnormality detection circuit 44 for this purpose, and these are connected in parallel to the input side of the OR circuit 42 together with the stop switch SW2.

Now, to explain the sequence control when stopping the TMP, in this embodiment, the stopping is performed in two stages: regenerative braking and DC braking. That is, as shown in FIG. 2, when a stop command is issued at t = t, the sequence control unit 11 enters the brake mode and immediately shifts the slip of the motor control circuit 1 to the opposite phase direction, thereby switching off the main power supply. Negative slip control is started using the DC voltage obtained from 31. As a result, the motor M operates as a generator and applies braking torque to the rotation of the rotor.

The regenerated power generated at this time is appropriately dissipated as heat internally. Then, when the rotor rotational speed N decreases and the regenerative braking force weakens, the sequence control unit 11 first sets the oscillation frequency F of the inverter to 0 at a certain point t-t2, and fixes only a specific phase in a conductive state. . As a result, direct current is directly applied to the motor M, and the braking shifts to direct current braking.

In this state, braking is performed efficiently at low speeds,
When the rotor rotation speed N reaches 0 and the rotation detection circuit 41 detects a stopped state, the brake mode of the sequence control section 11 is released.

During this time, the electromagnet control circuit 2 constantly introduces the electric power stepped down to the required voltage via the DC/DC converter 33 to keep the magnetic bearing functioning.

In the above configuration, in this embodiment, in addition to the main power source 31, a battery 5 and a regenerative power extraction means 12 capable of extracting regenerative power are provided, and when the main power source 31 cannot function, these auxiliary power sources can be used. We are trying to cover the necessary power supply by

The battery 5 has an input side connected to a charger 51 and a rectifier 32.
It is connected to the main power supply 31 through a switch S1 and a switch S2, and its output side is connected to a terminal S through a switch S1 and a switch S2. The switch S1 is open during normal operation, and closes its contacts upon receiving a signal from the power failure detection circuit 43 during a power outage.

Further, the switch S2 is closed during normal operation, and the contact is opened by inputting a detection signal related to a stop from the rotation detection circuit 41.

On the other hand, the regenerative power extraction means 12 is configured using a part of the motor control circuit 1 described above, and is configured to appropriately set the slip phase with respect to the inertial rotation of the rotor R when the power supply is stopped. This allows regenerated power to be obtained on the input side of the inverter. The regenerated power extracting means 12 is also equipped with a regulator and the like, so that a constant voltage can be extracted regardless of the level of rotation as long as the rotor rotation speed N is not insufficient. and,
The output from this regenerative power extraction means 12 is
It is connected to terminal a via a C converter 33.

Then, this terminal a and the above-mentioned terminal A are connected at their respective output sides via a diode D1 and a diode D2, and this is connected to the motor control circuit 1 and the electromagnet control circuit 2.
The signal is inputted to an appropriate drive terminal of the device. In other words, since the battery voltage vb is applied to the terminal at the time of a power outage, this voltage vb becomes the reference value, and the larger one of them is used for power supply depending on the magnitude relationship with the regenerative voltage Va applied to the terminal a. The smaller one has its associated diode D1 or D2 reverse biased to prevent current from flowing. Here, the regenerative voltage Va, which is slightly higher than the battery voltage Vb, is set to appear at the terminal a constantly as long as the rotor rotational speed N is not insufficient. Note that the diode D3 is used for bias to compensate for the motor M momentarily falling into a non-driving state during a power outage using battery power.

Next, the operation of this embodiment at the time of power outage will be explained. Main power supply 31
When there is a power outage, the power supply to the motor control circuit 1 and the electromagnet control circuit 2 is cut off, and at the same time, the power outage detection circuit 43 closes the switch S1 and the battery voltage V is applied to the terminal.
b appears, and D from the regenerative power extraction means 12
Regenerative voltage V is applied to terminal a via C/DC converter 33.
a is introduced. Assuming that rotor R was rotating at a medium speed range or higher before the power outage, regenerative voltage Va > battery voltage Vb
Therefore, diode D1 becomes conductive and regenerated power is supplied to motor control circuit 1 and electromagnet control circuit 2, and diode D2 becomes reverse biased to prevent power consumption of battery 5. In addition, in parallel with the above, the power outage detection circuit 43 issues a power outage command to the sequence control unit 11 via the OR circuit 42 at the same time as the power outage, so the sequence becomes the brake mode and 1=1 in FIG. ．． Regenerative braking corresponding to the time has started.

When the rotor rotational speed N decreases and the regenerative voltage Va falls below the battery voltage vb, the diode D2 is now forward biased and conductive, and the battery 5 is connected to the motor control circuit 1 and the electromagnet control circuit 2. electricity will be supplied. On the other hand, diode D1
is reverse biased, so the regenerated power is transferred to the motor control circuit 1.
Heat is dissipated within.

When the rotor rotational speed N further decreases and the regenerative braking weakens,
At a time point corresponding to 1=12 in FIG. 2, the motor control circuit 1 shifts to DC braking and continues forced braking to the rotor R. When the rotor R finally stops completely, the switch S2 is opened by a signal from the rotation detection circuit 41, the battery 5 is disconnected, and the brake mode of the sequence control section 11 is released. Also, here the rotor R reaches the T and D states.

Therefore, with the above configuration, it is possible to reduce the dependence on the battery until the TMP stops, and it is also possible to stop the TMP more quickly. In other words, at medium speeds and above, regenerative braking and electromagnetic drive can be covered by regenerative power, and the battery 5 does not need to consume power.When the regenerative power is switched to the battery 5, regenerative braking is switched to DC braking. This is because braking can be carried out in an effective range at all times by suitably taking over the braking process.

As a result, even if a power outage occurs for a long time or repeatedly, the battery 5 will not run out of charge, reducing the burden on the T and D bearings and effectively avoiding the risk of T and D damage. At the same time, it becomes possible to ensure smooth stopping operation. Further, with such a structure, even if the battery 5 is undercharged for some reason, the brake operation will be performed reliably to extend the life of the T and D bearings. Furthermore, battery 5
However, it can be made small, which also contributes to cost reduction. Furthermore, since this device does not require a program circuit such as a timer in the sequence control system for stopping the TMP, troubles such as malfunctions and failures caused by this type of circuit can be avoided.

Although one embodiment of the present invention has been described above, the circuit configuration and the like are not limited to those of the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] As described above, the present invention has a configuration in which a part of the power supply is covered by regenerative power, thereby reducing dependence on the battery during power outages and preventing discharge as much as possible. It is possible to provide a power supply device that can efficiently supply power to the magnetic bearing and reliably drive the magnetic bearing until the TMP is stopped.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a circuit diagram, and FIG. 2 is a circuit diagram.
The figure is an explanatory diagram of the action.

Claims (1)

[Claims] This is applied to a turbo molecular pump comprising an electromagnet that applies a magnetic force to a rotor, and an electromagnet control circuit that drives the electromagnet to function as a magnetic bearing, and the electromagnet control circuit is supplied with power. What can be done is to install at least a battery in addition to the main power supply and a regenerative power extraction means that can extract regenerative power using the rotation of the rotor, so that even if the main power supply stops, even if the regenerative voltage is higher than the reference value, A power supply device for a turbo molecular pump, characterized in that the battery voltage is applied to the electromagnet control circuit, and when the regenerative voltage is less than a reference value, the battery voltage can be applied to the electromagnet control circuit.