Electricity: motive power systems – Automatic and/or with time-delay means – Speed or rate-of-movement
Reexamination Certificate
2000-05-25
2001-09-11
Ip, Paul (Department: 2837)
Electricity: motive power systems
Automatic and/or with time-delay means
Speed or rate-of-movement
C318S779000, C318S801000, C318S807000, C318S808000, C323S318000, C323S344000, C323S351000, C417S356000
Reexamination Certificate
active
06288510
ABSTRACT:
TECHNICAL FIELD
This invention concerns a drive control device for controlling a motor driven high-speed rotor unit and a discriminating method used in the drive control device to discriminate among different types of rotor units which are to be controlled. More specifically, it concerns a drive control device for controlling the drive applied to a high-speed rotor unit with magnetic bearings such as that in a turbo molecular pump, a compressor or turbine, or applied to the spindle in a rotor tool unit, and the discriminating method used in the drive control device to discriminate among these different types of rotor units.
TECHNICAL BACKGROUND
Magnetic bearings experience less loss than traditional hydrodynamically lubricated bearings. Being dry, they can be used in a clean atmosphere. They are also particularly practical for use in a vacuum state. For these reasons, magnetic bearings have come to be widely used to support the rotating parts of high-speed rotor units driven directly by motors, such as the rotors in turbo molecular pumps.
A high-speed rotor unit supported by magnetic bearings, such as a turbo molecular pump, would typically have the configuration shown in FIG.
9
. Pump unit A and power supply unit B are electrically connected via cables
40
. On side A are the pump itself; motor
29
, which is directly connected to the pump; magnetic bearings
9
, which maintain the position of the rotor of the motor
29
and the rotating portion of the pump connected directly to that rotor; and position sensors
24
, which detect the gaps between the bearings and the rotor.
Power supply unit B comprises motor drive circuit
34
(a power supply circuit which possibly includes an inverter circuit) for driving motor
29
, which is directly connected to the rotor; magnetic bearing control circuit
32
and magnetic bearing drive circuit
33
, which receive the signals from the aforementioned position sensors
24
and control the drive voltages to magnetic bearings
9
(electromagnets) so as to keep the rotor centered; and magnetic bearing power supply
31
, which supplies power to drive the magnetic bearings. Units A and B are connected by cables
40
A through
40
C.
Each of the control and drive circuits,
32
and
33
, in power supply unit B configured as described above must be adjusted or set according to the type of pump unit used.
Magnetic bearing Control circuit
32
controls the magnetic bearings to keep the rotor centered in one embodiment of this invention which will be discussed shortly. This magnetic bearing control circuit comprises, as shown in
FIG. 4
(A), a PID control circuit
62
equipped with a comparator element, an integrator element and a differentiator element; a phase compensator circuit
63
, which stabilizes the vibrations with a plurality of dimensions resulting from the configuration of the rotor; filter circuit
61
(a notch filter, a low pass notch filter, a low pass filter or a phase filter); and a bias circuit
65
, which applies bias current in order to assure that magnetic bearings
9
can rigidly bear the static load imposed by the rotor. Each of these circuits must be adjusted by setting different constants depending on the type of rotor unit being driven.
Also in motor drive circuit
34
, if the inverter is to be operated such that V/f remains constant, not only the constants needed to control rotation by maintaining the rated voltage and frequency, but also various additional constants must be set to protect the rotor unit from overvoltage, overcurrent, overload and excessively high frequency inputs.
For this purpose, limit element circuit cards
32
A to
34
A are built into control circuit
32
and drive circuits
33
and
34
in power supply unit B for each type of rotor unit.
In prior devices, then, the pump unit A for a given type of rotor unit must be matched with a particular power supply unit B. The proper units A and B must be selected during assembly, and a power supply unit B and pump unit A selected for one type of rotor unit cannot be used for another type. Thus a different power supply unit must be selected for the pump unit used for each type of rotor unit. This severely compromises productivity. Such variation also poses a problem in terms of aftermarket administration and troubleshooting. If a number of different types of turbo molecular pumps are used, it becomes difficult to design the layout for the rotor units and the plant in which they are used. The installation will occupy a great deal of space, and maintenance will be troublesome.
To address these shortcomings, the present applicant proposed in Japanese patent application 8-317876 that the circuits in the power supply unit B be designed so as to limit the number of rotor unit types for which unit B would be applicable. According to the proposed design, which can be seen in FIG.
8
. element circuit cards
32
A through
34
A for each type of rotor unit are provided in pump unit A for bearing control circuit
32
and bearing and motor drive circuits
33
and
34
. Although this design allows power supply unit B to be used generally, it requires that each circuit such as bearing control circuit
32
and motor drive circuit
34
, be built into the unit for each type of rotor unit, which limits the interchangeability of pump unit A,. This raises the production cost and increases the size of the hardware which constitutes pump unit A, which prevents the entire device from being streamlined. Another problem is that turbo molecular pumps are sometimes placed in the vicinity of equipment used in the production of semiconductors, particularly equipment where reactive substances are present such as vacuum containers (or chambers). The equipment or countermeasures required to maintain reliability when such circuit boards are installed in such a location are very costly.
DESCRIPTION OF THE INVENTION
An object of this invention is to provide a drive control device for controlling the drive applied to a high-speed rotor unit which would have no circuits in either its pump unit A or its power supply unit B that would limit the use of the device with various types of rotor units, which could easily be used with various types of rotor units, and whose power supply unit B could be used generally; and to provide a discriminating method for discriminating among different types of rotor units which could be used in the drive control device.
Another object of this invention is to provide a drive control device for controlling the drive applied to a high-speed rotor unit in a pump unit or the like which would not have any control boards in the pump unit, and to provide a discriminating method for discriminating among different types of rotor units which could be used in the drive control device. This would simplify the configuration of the unit, improve productivity, simplify aftermarket service, and enable a single type of power supply to be used with a number of different pump units. It will make it easier to design a device or a plant in which the pump unit is used. The device or plant will be smaller and easier to maintain.
In order to address the shortcomings outlined above, the present invention is designed as follows. The drive control device for controlling a high-speed rotor unit has a high-speed rotor unit and a power supply unit B. The high-speed rotor unit is equipped with magnetic bearings comprising electromagnets at the rotor or the stator. The rotor is supported in mid-air by the magnetic force of the bearings as it is made to rotate at high speed, and the specified load function is implemented. The power supply unit B is equipped with a magnetic bearing control means to control the electric power applied to the magnetic bearings according to signals from position sensors in the high-speed rotor unit, and a motor drive control means to control the drive power applied to the rotor and stator of a motor.
This drive control device is distinguished by the configuration that the power supply unit contains a set of tables of constants needed to control the various types of rotor u
Crowell & Moring , L.L.P.
Ip Paul
Leykin Rita
Mitsubishi Heavy Industries Ltd.
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