Base plate, particularly for electrical machines

Details Base plate, particularly for electrical machines Base plate, particularly for electrical machines

1999-09-03

2001-08-14

Enad, Elvin (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S051000, C310S081000, C310S088000, C310S091000

Reexamination Certificate

active

06274956

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an end shield, particularly for electrical machines.
BACKGROUND INFORMATION
Electrical machines and the respective foundations have common natural system frequencies.
Systems composed of an electrical machine and foundation and whose natural system frequencies correspond to the excitation frequencies as rotational frequency and/or, preferably, in the case of 2-pole machines to twice the line frequency, lead to considerable vibration problems. These vibration problems are expressed in excessively high material stresses which lead to material damage if the permissible stress values of the material are exceeded. Moreover, large-scale functional impairments occur when certain deformation limits are exceeded which lead, for example, in the case of rotor vibrations of electric motors, to a bridging of the play between the rotor and housing. Motors which exhibit no vibration objections in acceptance tests where “hard” foundations are present can nevertheless lead to vibration problems for customers with “soft” foundations. It has so far been possible to conform to the vibration requirements of the standards and the customers only by methods which are complicated in terms of design and time-consuming such as, for example, by making changes to the foundation or the rotor (shaft diameter).
A further possibility of meeting these requirements consists in changing the bearing, for example, by changing the bearing span, by using sliding bearings instead of rolling bearings, or vice versa. These approaches entail high costs and lead to unplanned modification periods which lead to a loss of production for the customer.
SUMMARY
It is an object of the invention to be able to make quick and simple on-site changes to the typical natural system frequencies of the machine and foundation.
This object set is achieved according to the present invention by virtue of the fact that the end shield has at least two differently designed sectors. A sector is taken to mean both a circular section and an arbitrary region of the end shield. Different radial stiffnesses in the individual sectors are achieved by such a subdivision of the end shield into at least two differently designed sectors. By rotating the end shields in a plane perpendicular to the motor axis, it is possible to obtain motors of different stiffness, and, thus motors also of different natural frequencies. More than two differently designed sectors render it possible for the natural frequencies of the motors to be set in a stepwise fashion. Rotating the end shields can be performed on site without a large outlay. A substantial cost reduction and minimization of the conversion periods therefore result. The number of the sectors is rationally bounded above by the number of the fastening screws on the circumference of the end shield on the motor housing. If a further subdivision is provided, the sectors must be interconnected at their transition zones in such a way that they withstand the operating loads.


REFERENCES:
patent: Re. 35855 (1998-07-01), Blaettner et al.
patent: 5969447 (1999-10-01), Periyathamby et al.
Patent Abstracts of Japan, JP 08 107655 A, Apr. 23, 1996 (Matsushita Electric Inc. Co. Ltd.)*.*
Patent Abstracts of Japan, JP 02 028542 A, Nov. 6, 1990 (Toshiba Corp.)*.*
Patent Abstract of Japan, JP 57 028542 A, Feb 16, 1982*.

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