Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-11-30
2001-05-29
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S059000, C310S058000, C310S052000
Reexamination Certificate
active
06239522
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of electrical generators. It relates to a generator with a cooling system which draws in, from the generator, cooling medium heated by the heat-generating elements of the generator and which guides the hot cooling medium to at least two cooling units, which cooling units operate in parallel, and in which cooling system the cooling units cool the cooling medium before it is led back to the heat-generating elements of the generator.
BACKGROUND OF THE INVENTION
In generators, the problem generally arises that the ventilation work carried out on the cooling medium, the rotor surface friction and, in particular, the electrical losses in the conductor windings and the stator laminae lead to a large development of heat. This demands efficient cooling of the central components of the generator.
In the current increasingly widespread high performance generators, the ventilation losses in particular increase because of the increasing peripheral velocities and this makes careful design of the cooling systems essential. In such cooling systems, a cooling medium—usually air or another gas, and also liquid media in special cases—is normally driven through the generator in a cooling circuit. The heat occurring at the hot components of the generator is transported away by the cooling medium and is extracted again from the cooling medium by means of cooling units at another location in the cooling circuit.
In generators which are operated on the suction cooling principle, the cooling medium heated by the heat-generating elements of the generator is drawn in from the generator by main fans fastened to the rotor shaft. These main fans are normally arranged at the front and rear ends of the generator and a ducting system guides the cooling medium expelled by the main fans through cooling ducts to a cooling arrangement, which is usually located under the generator in a foundation pit. Heat is then extracted from the cooling medium as it flows through the cooling arrangement extending essentially over the complete length of the generator and composed of a plurality of cooling units operating in parallel. The cold medium is then ducted back, over the complete length, to the heat-generating elements within the generator, thus forming a closed cooling circuit.
In order to meet the current demands for cooling in machines operating at their performance limits, very efficient cooling systems with small flow losses and high efficiency are necessary. Particularly with respect to operational reliability and avoiding damage to the components, it is then necessary to ensure that the cooling system is as insensitive as possible to faults. This is, for example, achieved by installing a plurality of units, which operate in parallel and adjacent to one another in the cooling medium flow, instead of a single large cooling unit. Compensation for the failure of a cooling unit can, by this means, be at least partially provided by other units and destruction of the components due to overheating can be substantially avoided.
In modern generators, even the use of a plurality of cooling units operating in parallel cannot prevent components suffering damage in the case of a failure of even one unit. If, namely, a cooling unit fails, hot gas streaks immediately form behind the failed unit (behind in the flow direction) and these lead, within an extremely short time, to the critical material temperatures being exceeded in the components over which flow occurs. The situation is particularly critical in the case of the failure of boundary coolers because, in this case, strong and substantially isolated hot gas streaks occur immediately.
SUMMARY OF THE INVENTION
The invention is therefore based on the object of making means available in which
the formation of hot gas streaks is prevented in the case of the failure of individual coolers,
major modification to the conventionally used cooling systems does not become necessary
no significant pressure losses are generated.
This object is achieved, in a generator of the type mentioned at the beginning, by providing means which mix together the cooling medium flows flowing from different cooling units after they emerge from the cooling units and before they are supplied to the heat-generating elements of the generator.
A first preferred embodiment of the invention is characterized in that the mixing is effected by rigid guide plates being mounted in an equalizing space arranged downstream of the cooling units, which guide plates deflect the various cooling medium flows.
A further embodiment is characterized in that the guide plates mix together the cooling medium flows from respectively adjacent cooling units. This is, in particular, advantageous because antarbitrary number of cooling units, which are connected in parallel adjacent to one another, together with the guide plates can be provided in a modular manner and because it is possible to dispense with a bundling arrangement for the flows.
Another embodiment is based on the fact that the guide plates are arranged in the equalizing space in such a way that the cooling medium flows are provided with a vortex when they are mixed together. The result of this is that the mixing takes place much more efficiently.
In a particularly preferred embodiment, at least two guide plates are present which—starting from the sides adjoining one another of the adjacent cooling units—are extended to a ceiling level above the outlet surface of the cooling units in such a way that they engage in-one another in saw-tooth fashion in an alternating manner inclined towards the side of the one and of the other adjacent cooling unit. By this means, the equalizing space is subdivided into a distribution space and a mixing space, the distribution space being located directly behind the cooling units in the flow direction of the cooling medium and the mixing space being arranged immediately behind the distribution space in the flow direction of the cooling medium. The cooling medium flows of adjacent cooling units are mixed, in the mixing space, by the deflection at the guide plates in such a way that they are subjected to vortices when flowing from the distribution space to the heat-generating elements of the generator. In addition, a further advantage follows from the fact that the partial flows have counterflow relative to one another due to this guidance system and this, in the case of a failure of one unit, has the result of optimum heat exchange, due to the counterflow cooling, between the uncooled hot and cooled cooling medium flows.
Further embodiments are given by the subclaims.
REFERENCES:
patent: 4071791 (1978-01-01), Armor et al.
patent: 5883448 (1999-03-01), Zimmerman
patent: 27 24 422 (1981-01-01), None
patent: 196 45 272 (1998-05-01), None
Baumgartner Josef
Glahn Joern
Jung Michael
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Jones Judson H.
Ramirez Nestor
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