JPS60496Y2 - Magnetic bearing control device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to thrust control of a magnetic bearing during startup of a water turbine generator.

The idea of using a magnetic bearing device in a vertical water turbine generator to lift the rotor and appropriately reducing the load burden on the thrust bearing to facilitate startup has been known for a long time.

Generally, during operation, the electromagnetic winding of the magnetic bearing device is kept constantly excited.

However, when upward thrust is generated on the rotor due to fluctuations in the thrust of the water turbine, over-lifting may occur.

The purpose of the present invention is to prevent such over-lifting phenomenon at the time of startup.

The over-lifting phenomenon at startup occurs, for example, when the shaft of a water turbine cools and shrinks while the water turbine is out of operation, and the water turbine attached to the shaft is displaced upward with respect to the water turbine casing.

When started from this state, the water from when the kite vane is opened flows around the floating bottom of the water wheel, exerting upward pressure from the bottom of the water wheel, and is connected to the water wheel through the shaft. A phenomenon in which the rotor is pushed up can be seen.

Once the rotor is pushed up, the thrust of the excitation winding of the magnetic bearing is further enhanced, resulting in overlift.

Therefore, in order to prevent the above-mentioned over-lifting phenomenon, this invention has a magnetic bearing consisting of an armature provided on a shaft that rotates together with the water turbine and the generator rotor, and an excitation device facing the armature, and a thrust shaft fixed to the shaft. runner, a mechanical downward thrust bearing that constantly shares and supports part of the shaft's downward thrust load that is applied during operation through this thrust runner, and an upward water thrust that detects the load of the downward thrust bearing and causes the downward load to act on the water turbine. A control device for a magnetic bearing is comprised of a load detection element that detects a decrease in the magnetic bearing, and a control circuit that inputs a signal from the load detection element to control demagnetization of the excitation device of the magnetic bearing.

The configuration will be described below based on the drawings.

A shaft 2 to which a water turbine 1 is attached is connected to a shaft 2' on the generator side via a coupling 3, and a rotor 4 of the generator is provided on the shaft 2'.

A stator 5 is provided which is arranged concentrically with the rotor 4.

An armature 6 of a magnetic bearing 17 is provided on the shaft 2' of the rotor 4 on the side opposite to the water wheel.

An excitation device 7 facing the armature 6 is supported by the upper frame 8.

The upper frame 8 is supported by a frame and is loosely fitted to the shaft 2', and a thrust runner 11 is fixed to the shaft 2'.

In this way, in order to bear the upward thrust of the rotor 4 that occurs when the thrust fluctuates, the guide bearing metal 13 supported by the fixed part 9 provided on the upper frame 8 prevents the bearing from lateral vibration, and the upward thrust bearing 14 and ordinary downward thrust bearing 12
A thrust bearing 20 is configured.

Therefore, the disc spring 15 under the pad of the downward thrust bearing 12
A load detection element 16, such as a strain gauge, is disposed at.

The disc spring 15 deflects in proportion to the load, causing the load detection element 16 to produce a signal change.

A device A for converting and amplifying this signal into an electric signal, and a control device B for controlling and demagnetizing the input current of the excitation device 7 in response to the signal are provided.

Upon startup, an upward thrust is generated as shown in curves a (water thrust) and b (rotation speed) in FIG. 2.

In this case, the direction of the upward thrust is opposite to the downward axial thrust based on the weight of the water turbine and rotor, and the thrust load on the downward thrust bearing is reduced.

The load on the downward thrust bearing 12 at this time is detected by a load detection element such as a strain gauge, and the signal is sent to the amplifier circuit A.
While the input signal is present, the input current of the excitation device 7 is reduced to maintain a balance between the upward thrust and the downward thrust via the control circuit B.

As described above, the over-lifting phenomenon at the time of startup of the water turbine generator is detected by a detection element that detects the displacement of the disc spring 15 provided on the downward thrust bearing 12, for example, a known strain gauge, and the amount control circuit B in which the over-lifting state continues. The input current to the excitation device 7 is reduced to adjust the thrust.

Therefore, the device is extremely simple, and thrust adjustment can be easily and appropriately performed in a short time at startup.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the overall configuration of the water turbine generator, and FIG. 2 is a characteristic diagram. 1: Water turbine, 2, 2': Shaft, 3: Coupling, 4: Rotor, 5: Stator, 6: Armature, 7: Excitation device, 8: Upper frame, 9: Fixed part, 11 Nislast runner , 12: Downward thrust bearing, 13: Guide bearing metal, 14: Upward thrust bearing, 15: Disc spring, 16: Load detection element, 17: Magnetic bearing, 20 Nilus thrust bearing.

Claims (1)

[Scope of utility model registration request] A magnetic bearing consisting of an armature provided on a shaft that rotates together with the water turbine and generator rotor and an excitation device facing the armature, a thrust runner fixed to the shaft, and a downward direction of the shaft that is applied during operation through this thrust runner. A mechanical downward thrust bearing that always shares and supports part of the thrust load, a load detection element that detects the load of the downward thrust bearing and detects that it has been reduced by the upward water thrust acting on the downward loaded water turbine, and load detection. 1. A control device for a magnetic bearing, comprising a control circuit that inputs a signal from an element to control demagnetization of the excitation device for the magnetic bearing.