JPH0628498B2 - Electromagnetic shield used for rotation balance test of turbine generator rotor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electromagnetic shield that prevents a strong magnetic field from diffusing from the rotor to the surroundings in a rotation balance test performed under energization of a turbine generator rotor. Regarding the configuration of.

[Conventional technology]

In a large turbine generator, a phenomenon called vibration, which is called thermal imbalance, may occur in which vibration changes during operation due to excitation of the rotor. This is because, with respect to the exciting coil wound around the rotor of the generator, an increase in the coil temperature due to the exciting current causes local deformation of the rotor or imbalance in mass distribution.

Therefore, in order to confirm the occurrence of thermal imbalance in the completed rotor, it is necessary to pass a current having a value close to the rated current to the coil when performing the rotation balance test. However, if you perform a rotation balance test while the rotor is energized independently, a strong leakage magnetic flux will diffuse to the surroundings due to the magnetomotive force accompanying energization, so it is necessary to shield to prevent this. .

On the other hand, the magnetic shield method has been generally adopted as a means for shielding the magnetic flux leakage from the rotor. This magnetic shield system is one in which the rotor is surrounded by a cylindrical shield body made of laminated iron core having a structure similar to that of a stator core of a turbine generator, and its magnetic path is short-circuited. This is to prevent leakage magnetic flux of the rotor generated by energization during the rotation balance test from leaking outward from the shield body.

Separately from the magnetic shield method, a shield body made of a cylindrical aluminum or copper material is placed around the rotor,
An electromagnetic shield system has also been proposed in which leakage magnetic flux from the rotor is contained inside the shield body by utilizing the eddy current reaction.

[Problems to be solved by the invention]

By the way, in the above-mentioned magnetic shield system, the shield body is large and heavy, and considering the economical aspect, it is too large as a device temporarily used only during the rotation balance test, and the manufacturing cost is expensive. Also in the above-mentioned electromagnetic shield system, the electromagnetic shield body in which the material is changed from iron to aluminum or copper has a drawback that the manufacturing cost is high as in the magnetic shield system.

The present invention has been made in view of the above points, and an object thereof is to provide an electromagnetic shield used for a rotation balance test of a turbine generator rotor, which is inexpensive, lightweight, and has an effective shield performance. To do.

[Means for solving problems]

In order to solve the above-mentioned problems, according to the present invention, a short-circuit ring that surrounds a rotor and is provided at both left and right ends of the rotor, and is composed of a hollow conductor, and a cooling medium flows through the hollow conductor, and the short-circuit ring. The rotor is dispersed and installed so as to surround the outer circumference of the rotor, is composed of a hollow conductor, and includes a plurality of cage bars through which a cooling medium flows.

[Action]

With the above structure, the short-circuit ring and the cage bar form a reaction current loop surrounding the rotor. Further, the short-circuit ring and the cage bar are arranged at optimum positions corresponding to the magnetomotive force distribution on the rotor, and the cage bar is configured with a small arrangement pitch. Therefore, by arranging such a cage type electromagnetic shield so as to surround the rotor during the rotation balance test, the leakage magnetic flux which tends to diffuse from the rotor to the surroundings due to the energization is shielded by the eddy current reaction of the cage type electromagnetic shield. It can be contained inside to prevent leakage to the surrounding area. Moreover, it is cheaper and lighter in weight than the previously proposed electromagnetic shield configured as a cylindrical body of aluminum or copper. In the test actually conducted by the inventor, when a magnetic flux density measuring search coil was placed inside and outside the cage type electromagnetic shield, measurement was performed, and a shielding effect almost comparable to the electromagnetic shield body composed of the cylindrical plate was obtained. It has been confirmed.

In addition, the short-circuit ring and cage bar that compose the cage-type electromagnetic shield are made of hollow conductors, and a cooling medium such as water is made to flow through the interior during the test to effectively generate heat generated in the electromagnetic shield. Can be cooled.

〔Example〕

1 and 2 show the structure of a cage type electromagnetic shield based on an embodiment of the present invention, in which 1 is a rotor of a turbine generator, 2 is a shaft, 3 is between magnetic poles of a rotor coil. The crossover portion 4 is a slip ring for supplying power to the rotor coil,
Reference numeral 5 denotes an exciting power source, and in such a rotor, a shaft 2 is supported on a bearing 6 in a rotation balance test, and a test is conducted by driving the rotor at a high speed by a driving device (not shown) while energizing a coil. .

On the other hand, in the above rotation balance test, in order to prevent the strong leakage magnetic flux from the rotor from diffusing to the surroundings, the cage type electromagnetic shield 7 is provided so as to surround the periphery of the rotor. This cage type electromagnetic shield 7
The configuration is such that the short-circuit rings 8 made of a conductive material are disposed at the left and right ends of the rotor so as to face the inter-magnetic pole span portion 3 of the rotor coil.
9 and the rotor 1 straddling between the short-circuit rings 8 and 9.
As an assembly with a cage bar 10 consisting of a number of straight conductors surrounding the circumference of the.

The shorting rings 8 and 9 and the cage bar 10 are both made of hollow conductors, and
Both ends of 10 are connected to the internal space of the short-circuit rings 8 and 9 and are connected to each other. Further, for example, a water cooling type cooling system 14 including an insulating hose 11, a pump 12, and a cooler 13 is connected between the short-circuit rings 8 and 9, and between the cooling system 14 and the cage type electromagnetic shield 7. A refrigerant circulation path is formed through the hollow short-circuit rings 8 and 9 and the cage bar 10.

By arranging the cage type electromagnetic shield 7 having such a configuration so as to surround the rotor 1 during the rotation balance test, the magnetic flux generated by the magnetomotive force due to the energization of the rotor rotating at high speed and the electromagnetic shield 7 are linked. Thereby forming a reaction current loop between the cage bar 10 and the short-circuit rings 8, 9. Further, in this case, the current flowing in the electromagnetic shield flows so as to compensate the magnetomotive force of the rotor coil. As a result, the leakage magnetic flux from the rotor 1 is contained inside the electromagnetic shield, and diffusion to the surroundings is prevented. Further, with respect to the magnetomotive force generated in the magnetic pole crossing portion 3 of the rotor coil, the short-circuiting rings 8 and 9 surrounding the magnetomotive force exert an electromagnetic shield effect. The Joule heat generated in the electromagnetic shield itself by this operation is removed by the cooling medium flowing through the electromagnetic shield 7 through the external cooling system 14, thereby preventing abnormal overheating of the device.

〔The invention's effect〕

As described above, according to the present invention, the electromagnetic shield used in the rotation balance test, the short-circuit ring that surrounds the rotor and is provided at the left and right ends of the electromagnetic shield, and the outer circumference of the rotor across the short-circuit ring. Since the cage bar is composed of a plurality of cage bars that are distributed and installed so as to surround the electromagnetic shield, it is possible to provide an electromagnetic shield that is lightweight, inexpensive, and has a high shielding effect.

[Brief description of drawings]

1 and 2 are a side view and a sectional view showing the structure of an electromagnetic shield according to an embodiment of the present invention shown together with a rotor. In each figure, 1: rotor, 2: axis, 3: magnetic pole crossing portion of rotor coil, 4: slip ring, 5: excitation power supply, 7: electromagnetic shield, 8, 9: short-circuit ring, 10: cage bar, 14: Cooling system.

Claims (2)

[Claims] 1. An electromagnetic shield for use in a rotation balance test of a turbine generator rotor under energization, which is provided on both left and right ends of the rotor so as to surround the rotor, and is made of a hollow conductor, and is internally cooled. A short-circuit ring for allowing the medium to flow therethrough, and a plurality of cage bars that are laid across the short-circuit ring so as to be dispersed and installed so as to surround the outer periphery of the rotor and that are made of hollow conductors and that allow the cooling medium to flow therethrough. An electromagnetic shield used for a rotational balance test of a turbine generator rotor, which is characterized by comprising 2. An electromagnetic shield according to claim 1, wherein the short-circuit ring is arranged in the peripheral region of the rotor coil so as to face the portion between the magnetic poles of the rotor coil. Electromagnetic shield used for rotation balance test of child.