JP2001124076A - Thrust magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To save the electric power of a thrust magnetic bearing device, and to reduce the capacity and the size of a power amplifier. SOLUTION: Filter circuits 15-a, 15-b for removing PWM carrier frequency component are mounted on the output parts of PWM power amplifiers 14-a, 14-b, and the current is supplied to thrust electromagnets 3-a, 3-b through the filter circuits to reduce the carrier frequency component of a power amplifier included in the electric current flowing in the thrust electromagnets, and reduce the eddy current flowing to electromagnetic cores 4-a, 4-b. As a result, the power used in the device can be saved, the heat produced by the thrust electromagnets can be reduced, which simplifies a cooling mechanism, and reduces an amount of the electric current to be supplied to the electromagnet thereby reducing the capacity, the size and the cost of the power amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thrust magnetic bearing device which stably supports a rotating shaft in a non-contact manner in the axial direction by magnetic attraction of an electromagnet, and more particularly to a thrust magnetic bearing using a PWM power amplifier. Related to the device.

[0002]

2. Description of the Related Art A conventional thrust magnetic bearing device using a PWM power amplifier will be described with reference to FIG. FIG. 5 shows an axial section and a control circuit of a general thrust magnetic bearing device. In FIG. 5, reference numeral 1 denotes a rotating shaft, on the end of which a thrust disk 2 made of a magnetic material is fixed. Electromagnets 3-a and 3-b are provided at predetermined positions at positions facing each other with the thrust disk 2 sandwiched in the axial direction. These electromagnets 3-a and 3-b use solid magnetic materials as iron cores 4-a and 4-b, respectively, and have annular grooves 5 provided in the respective electromagnetic cores. Concentrically wound electromagnet coil 6-a,
6-b is inserted. The electromagnets 3-a and 3-b are firmly fixed to the frame 7.
Reference numeral 8 denotes a displacement sensor, which is attached to the frame 7 to detect the axial displacement of the shaft end of the rotating shaft 1.

Reference numeral 9 denotes a touch bearing composed of a ball bearing, a roller bearing, or the like. The touch bearing 9 is spaced from the rotary shaft 1 in the axial direction and the radial direction by a bearing bracket 10 with a smaller gap than the air gap of the magnetic bearing device. 7 is fixed. Reference numeral 11 denotes an amplifier for the displacement sensor signal, and the rotation axis 1 detected by the displacement sensor 8
Is converted into an electric signal. A control device 12 receives an output signal of the signal amplifier 11 and generates a control signal for stably supporting the rotating shaft 1. Reference numeral 13 denotes a phase inverter, which inverts the phase of the output signal from the control device 12. Reference numerals 14-a and 14-b denote PWM power amplifiers, which amplify the power of the output signal of the control device 12 and the output signal of the phase inverter 13, and output the thrust electromagnets 3-a and 3-b.
A current is supplied to each of the electromagnet coils 6-a and 6-b.

[0004] The conventional thrust magnetic bearing device having the above configuration operates as follows. The axial displacement of the rotating shaft 1 is detected by a thrust displacement sensor 8 and converted into an electric signal by a signal amplifier 11. The converted electric signal of the axial displacement is converted into a control signal for stably supporting the rotating shaft 1 by the control device 12, and one control signal is directly transmitted as it is, and the other control signal is transmitted through the phase inverter 13. hand,
The power is amplified by the power amplifiers 14-a and 14-b, respectively, and supplied to the electromagnet coils 6-a and 6-b of the thrust electromagnets 3-a and 3-b as current signals. Each of the thrust electromagnet 3-a and the thrust electromagnet 3-b is
A magnetic attraction force corresponding to the input control current is generated on the thrust disk 2, and the rotating shaft 1 is rotatably stably supported in a non-contact manner.

Thus, the power amplifiers 14-a, 14-
By adopting a PWM type as b, power loss in the power amplifiers 14-a and 14-b is minimized, energy saving is achieved, and the power amplifiers 14-a and 14-b are used.
-B is also made compact.

[0006]

However, in the conventional thrust magnetic bearing device having the above-described structure, the power amplifiers 14-a and 14-b employ the PWM method, and the thrust electromagnets 3-a and 3-b are not used. Since solid magnetic materials are used for the electromagnet cores 4-a and 4-b, the eddy current of the carrier frequency components of the power amplifiers 14-a and 14-b in the thrust electromagnets 3-a and 3-b is reduced. The flow caused eddy current loss in the electromagnet cores 4-a and 4-b, causing the thrust electromagnets 3-a and 3-b to generate heat and unnecessary power consumption.

The present invention has been made in view of such a conventional problem. A filter circuit is provided at the output of a power amplifier, and a current is supplied to the thrust electromagnet through the filter circuit. The carrier frequency component of the power amplifier included in the flowing current is reduced, the eddy current flowing through the electromagnet core is reduced, and as a result, the power consumption of the device can be reduced, and the heat generated by the thrust electromagnet can be reduced, simplifying the cooling mechanism. It is another object of the present invention to provide a thrust magnetic bearing device capable of reducing the amount of current supplied to the electromagnet and reducing the capacity, size, and cost of the power amplifier.

[0008]

According to a first aspect of the present invention, an annular groove is formed in an iron core attached to a frame casing, and a concentrically wound coil is inserted into the groove to form a thrust electromagnet. Then, the thrust electromagnet and another thrust electromagnet formed in the same manner are opposed to each other with a thrust disk firmly fixed to a rotating shaft between the thrust electromagnet and the thrust electromagnet sandwiched therebetween, and the rotation detected by the displacement sensor. The control unit converts the axial displacement signal of the shaft into a control signal for stably supporting the rotary shaft, converts the control signal into a current by a PWM power amplifier, supplies the current to the coil of the thrust electromagnet, and fixes the current to the rotary shaft. A thrust magnetic bearing device for stably supporting a thrust disk in the axial direction.
A filter circuit for removing a carrier frequency component in a current is provided between the power amplifier and the thrust electromagnet.

In the thrust magnetic bearing device according to the first aspect of the present invention, a displacement sensor detects an axial displacement signal of the rotating shaft, and the control device converts the displacement signal into a control signal for stably supporting the rotating shaft. The signal is converted into a current by a PWM power amplifier and supplied to the coil of the thrust electromagnet, thereby stably supporting the thrust disk fixed to the rotating shaft in the axial direction.
Then, the current from the PWM power amplifier is passed through a filter circuit, thereby removing a PWM carrier frequency component contained in the current.

Thus, the eddy current flowing through the electromagnet core of the thrust electromagnet is reduced, and the heat generated by the thrust electromagnet is also reduced.

According to a second aspect of the present invention, in the thrust magnetic bearing device of the first aspect, a band elimination filter circuit for removing only the carrier frequency component is used as the filter circuit. A circuit removes a PWM carrier frequency component from the current supplied from the PWM power amplifier to the thrust electromagnet.

According to a third aspect of the present invention, in the thrust magnetic bearing device of the first aspect, a high frequency inductance filter circuit is used for the filter circuit, and the high frequency inductance filter circuit supplies a thrust electromagnet from a PWM power amplifier. The PWM carrier frequency component is reduced from the current to be applied.

According to a fourth aspect of the present invention, in the thrust magnetic bearing device of the first to third aspects, the PWM circuit bypasses the filter circuit in a transient state such as acceleration or deceleration or a load change.
The output current of the power amplifier is directly supplied to the thrust electromagnet.
A changeover switch for switching the output current of the WM power amplifier to be supplied to the thrust electromagnet is provided. In a load situation requiring large power, the output of the PWM power amplifier is directly supplied to the thrust electromagnet, In a stable load situation, the output of the PWM power amplifier is supplied to the thrust electromagnet via the filter circuit.

According to a fifth aspect of the present invention, in the thrust magnetic bearing device of the fourth aspect, the changeover switch switches according to a fluctuation level of an output signal of the displacement sensor. The output of the PWM power amplifier is directly supplied to the thrust electromagnet, and the output of the PWM power amplifier is supplied to the thrust electromagnet via the filter circuit in a situation where the axial fluctuation of the rotating shaft is small.

According to a sixth aspect of the present invention, in the thrust magnetic bearing device of the fourth aspect, the changeover switch is switched according to a fluctuation level of an output signal of the control device, and the axial fluctuation of the rotary shaft is large. In a situation where the fluctuation level of the output signal of the control device is large, the output of the PWM power amplifier is directly supplied to the thrust electromagnet, and in a situation where the fluctuation level of the rotation signal in the axial direction is small and the fluctuation level of the output signal of the control device is small, the PWM power The output of the amplifier is supplied to a thrust electromagnet via a filter circuit.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment of a receiving device for a thrust magnetic bearing according to the present invention. In this thrust magnetic bearing device, reference numerals 1 to 14 denote the same components as those of the conventional example shown in FIG. 5, and function in the same manner to stably support the rotary shaft 1 in the axial direction. I do.

The features of the first embodiment are as follows:
a, 15-b. These filter circuits 15-a and 15-b are band elimination filter circuits having the filter circuit characteristics shown in FIG.
The output signals of the PWM power amplifiers 14-a and 14-b are input, and only the PWM carrier frequency (fc) component included in the current output of the power amplifiers 14-a and 14-b is removed. a, 3-b electromagnet coil 6
-A, 6-b.

In the thrust magnetic bearing device according to the first embodiment, the basic structure of the rotary shaft 1 and the thrust electromagnets 3-a and 3-b is basically the same as that of the conventional example.
The original function of the thrust magnetic bearing device works in the same manner as in the prior art.

Then, the PWM power amplifiers 14-a, 14
-B Filter circuits 15-a, 1 provided for each output
By 5-b, the PWM carrier frequency component included in the output of the power amplifier is removed, and the electromagnet coils 6-a and 6-b are removed.
b is supplied with a high-frequency free current. Thus, the current flowing through the electromagnet coils 6-a and 6-b has almost no PWM carrier frequency component of the power amplifiers 14-a and 14-b, and almost no eddy current flows through the electromagnet cores 4-a and 4-b. The heat generation due to eddy current can be reduced. Therefore, power saving and simplification of the cooling mechanism can be achieved with respect to the conventional thrust magnetic bearing device, and the current contained in the thrust electromagnets 3-a and 3-b is reduced. Compactness and cost reduction can be achieved.

The above filter circuits 15-a, 15-
The same operation and effect can be achieved by using a high frequency inductance filter circuit that can suppress the passage of the carrier frequency (fc) component for -b.

Next, a thrust magnetic bearing device according to a second embodiment of the present invention will be described with reference to FIG. The second embodiment is characterized in that the input connections to the electromagnet coils 6-a and 6-b are different from the first embodiment shown in FIG. 1 in that the PWM power amplifiers 14-a and 14-b Switches 17-a and 17-b for switching between the direct output of the filter circuit 15-a and the output of the filter circuits 15-a and 15-b, and the output of the displacement sensor 8 for switching these switches 17-a and 17-b. Switching device 16 which performs according to the fluctuation level of the signal
And the addition of

In the thrust magnetic bearing device of the second embodiment, as in the first embodiment, the basic structure such as the configuration and arrangement of the rotating shaft 1 and the thrust electromagnets 3-a and 3-b is the same as that of the first embodiment. As in the example, the original function of the thrust magnetic bearing device operates in the same manner as in the related art.

Then, the displacement sensor 8 is switched by the switch 16.
Are switched to the direct output sides of the power amplifiers 14-a and 14-b when the fluctuation level of the displacement amount of the rotating shaft 1 detected by the switch is large, and when the fluctuation level is small to some extent, the changeover switch 17-a or 17-b is switched. −a,
17-b is switched to the output side of the filter circuits 15-a and 15-b.

As a result, the outputs of the power amplifiers 14-a, 14-b are changed over by the changeover switches 17-a, 17-b when the rotation of the rotary shaft 1 rises and falls, or when a large control force is required due to a disturbance force. b, the electromagnetic coils 6-a, 6-
Since the voltage is directly supplied to b, high-speed response control is possible without affecting the frequency response of the control system. During a relatively long stable period in which high-speed response control is not required, the changeover switches 17-a and 17-b are connected to the filter circuit 15
-A and 15-b are switched so as to be supplied to the electromagnet coils 6-a and 6-b.
a, 14-b, the current in which the PWM carrier frequency component has been reduced or removed from the output current is the electromagnet coil 6-a,
6-b, and the electromagnet cores 4-a, 4
-B eddy current is reduced. As a result, eddy current loss is reduced, power saving and simplification of the cooling mechanism become possible, and the time required for high-speed response control is relatively short. In addition, the power amplifiers 14-a and 14-b can be reduced in capacity, size, and cost.

Next, a third embodiment of the thrust magnetic bearing device of the present invention will be described with reference to FIG. The feature of the third embodiment lies in that the fluctuation level of the output of the control device 12 is used for the switching signal of the switch 16 as compared with the second embodiment shown in FIG. All other components are common to the second embodiment.

In the third embodiment, the switch 16 switches the switches 17-a and 17-b in accordance with the fluctuation level of the output signal of the control device 12, and the power amplifiers 14-a and The PWM carrier frequency of 14-b is set lower or higher than other bearings, for example, a radial magnetic bearing (not shown), so as not to affect the control.

Thus, in the thrust magnetic bearing device according to the third embodiment, a large control force is required when the rotation of the rotary shaft 1 rises and falls or when a disturbance force is applied, as in the second embodiment. Power amplifiers 14-a, 14-b
Are directly supplied to the electromagnet coils 6-a and 6-b by the changeover switches 17-a and 17-b, thereby enabling high-speed response control without affecting the frequency response of the control system. In a relatively long stable period in which high-speed response control is not required, the changeover switches 17-a and 17-b switch the output of the filter circuits 15-a and 15-b to the electromagnetic coil 6-a.
a, 6-b, and the current from which the PWM carrier frequency component is reduced or removed from the output current of the power amplifiers 14-a, 14-b is supplied to the electromagnet coils 6-a, 6-b. As a result, the eddy current of the electromagnet cores 4-a and 4-b decreases. In addition, in the case of the third embodiment, the power amplifiers 14-a, 14-
If the PWM carrier frequency of b is set lower than that of the other bearings, the electromagnet coils 6-a and 6-6 can be used even if the changeover switches 17-a and 17-b are switched to the direct outputs of the power amplifiers 14-a and 14-b. The PWM carrier frequency component flowing to -b can be made smaller. Conversely, if the PWM carrier frequency is set higher than other bearings, the constants of the filter circuits 15-a and 15-b can be small.

Accordingly, in the third embodiment, power saving and simplification of the cooling mechanism can be achieved in the same manner as in the second embodiment. The power amplifiers 14-a and 14-b and the filter circuits 15-a and 1
5-b, selector 16 and selector switch 17-a, 1
7-b can be constituted by one unit, and the circuit can be simplified and compact.

Further, power amplifiers 14-a and 14-b
The eddy current flowing through the thrust electromagnets 3-a and 3-b can be reduced without passing through the filter circuits 15-a and 15-b by setting the PWM carrier frequency of the other bearings lower than that of the other bearings. Power saving and simplification of the cooling mechanism can be achieved. Conversely, P of the power amplifiers 14-a and 14-b
By setting the WM carrier frequency higher than that of the other bearings, the constants of the filter circuits 15-a and 15-b can be reduced, power saving and simplification of the cooling mechanism can be achieved. a, 15-b can be reduced in size and cost.

[0030]

As described above, according to the first to third aspects of the present invention, the current from the PWM power amplifier is passed through the filter circuit to remove or reduce the frequency component of the PWM carrier contained in the current. By doing so, the eddy current flowing through the electromagnet core of the thrust electromagnet can be reduced, and the heat generated by the thrust electromagnet can be reduced.
The cooling mechanism can be simplified and the current contained in the thrust electromagnet can be reduced, so that the power amplifier can be reduced in capacity, size and cost.

According to the invention of claims 4 to 6, claims 1 to 1
In addition to the effects of the third aspect, the switching operation of the changeover switch directly supplies the output of the PWM power amplifier to the thrust electromagnet in a load situation requiring large power, and outputs the output of the PWM power amplifier in a stable load situation. Since the thrust electromagnet is supplied via the filter circuit, the output of the power amplifier is directly supplied to the electromagnet coil when the rotation of the rotating shaft rises and falls and when a large control force is required due to disturbance force. High-speed response control is possible without affecting the frequency response of the control system, and during a relatively long stable period when high-speed response control is not required, the output of the filter circuit is supplied to the electromagnetic coil and the power amplifier The current in which the PWM carrier frequency component has been reduced from the output current is supplied to the electromagnet coil, and the eddy current of the electromagnet core is reduced. Rukoto can, eddy current loss is reduced,
Power saving and simplification of the cooling mechanism are possible, and the time required for high-speed response control is relatively short. Miniaturization and cost reduction are possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a graph showing characteristics of a filter circuit employed in the embodiment.

FIG. 3 is a block diagram showing a configuration according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotation axis 2 Thrust disk 3-a, 3-b Thrust electromagnet 4-a, 4-b Electromagnet core 5 Annular groove 6-a, 6-b Electromagnet coil 7 Frame 8 Displacement sensor 11 Signal amplifier 12 Control device 13 Phase inverter 14-a, 14-b Power amplifier 15-a, 15-b Filter circuit 16 Switch 17-a, 17-b Switch

Claims (6)

[Claims] An annular core is provided in an iron core attached to a frame casing, and a coil wound concentrically is inserted into the groove to form a thrust electromagnet. Another thrust electromagnet, and a thrust disk firmly fixed to the rotating shaft between them is opposed to each other with the thrust disk sandwiched in the axial direction, and the axial displacement signal of the rotating shaft detected by the displacement sensor is transmitted to the control device by the control device. The control signal is converted into a control signal for stably supporting the rotating shaft, and the control signal
In a thrust magnetic bearing device which converts the current into a current by a power amplifier and supplies the current to the coil of the thrust electromagnet, and stably supports a thrust disk fixed to the rotating shaft in the axial direction, between the PWM power amplifier and the thrust electromagnet A thrust magnetic bearing device comprising a filter circuit for removing a carrier frequency component in a current. 2. The thrust magnetic bearing device according to claim 1, wherein the filter circuit is a band elimination filter circuit that removes only the carrier frequency component. 3. The thrust magnetic bearing device according to claim 1, wherein the filter circuit is a high-frequency inductance filter circuit. 4. In a transient state such as acceleration or deceleration or a load change, the output current of the PWM power amplifier is directly supplied to the thrust electromagnet by bypassing the filter circuit, and the PWM is supplied via the filter circuit during stable rotation. The thrust magnetic bearing device according to any one of claims 1 to 3, further comprising a changeover switch for switching an output current of a power amplifier to be supplied to the thrust electromagnet. 5. The thrust magnetic bearing device according to claim 4, wherein the changeover switch switches according to a fluctuation level of an output signal of the displacement sensor. 6. The thrust magnetic bearing device according to claim 4, wherein the changeover switch switches according to a fluctuation level of an output signal of the control device.