Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-07-26
2001-12-04
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S054000
Reexamination Certificate
active
06326709
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a cooling system for cooling the stator and/or the rotor of a generator, and to a method for cooling the stator and/or the rotor of a generator.
A hydrogen-cooled synchronous generator with a water-cooled stator winding is described in the book “Synchronmaschinen” [Synchronous Machines], AEG Telefunken Handbücher, Volume 12, Berlin 1970, on page 53. Generators with a water-cooled stator winding require a water loop. It comprises pumps for circulating the primary cooling water, return coolers and filters which ensure that the stator winding is not soiled, and an expansion vessel which is fitted on top on the machine. Fine filters and an ion exchanger for preparing the water are connected in the shunt circuit to this main circuit. Since the cooling water must be fed to the stator winding via insulating hoses, a small fraction of hydrogen can diffuse via them from the machine interior into the water circuit. This hydrogen fraction is given the opportunity of degassing from the water in the not entirely filled expansion vessel. It is led to the outside via a pressure control valve and a gas meter.
German patent application DE 22 22 487 describes a device for removing non-absorbed gases in liquids in the case of liquid-filled electric machines. In accordance with
FIGS. 1 and 2
of that document, two concepts are applied for a cooling circuit. On the one hand, a coolant compensating container via which coolant is supplemented is connected to the cooling circuit via a spur line. In that compensating container which is disposed outside of the cooling circuit, a degassing container through which the entire coolant flow passes is connected into the cooling circuit. Outgassing of the coolant occurs in the degassing container. The gases are discharged to the outside. In accordance with the other concept, the compensating container for the coolant is integrated into a shunt circuit connected in parallel with the main cooling circuit. In this case, a smaller coolant flow of the shunt circuit passes continuously through the compensating container which serves simultaneously as a degassing container.
A cooling water circuit for a water-cooled electric machine is described with the aid of FIG. 5 in Siemens-Zeitschrift [Siemens Journal], Vol. 41, 1967, issue 10, pages 838-39. The cooling water must have a low electric conductivity for reasons of insulation. For this reason, chemical filters or ion exchangers, which continuously reduce the ion concentration in the cooling water, are connected into the cooling circuit.
SUMMARY OF THE INVENTION
The object of the invention is to provide a cooling system and a method of cooling a generator, i.e., the stator and/or the rotor of the generator, which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this kind, and which is simple and cost-effective.
With the above and other objects in view there is provided, in accordance with the invention, a cooling system for cooling a generator, comprising:
a cooling circuit;
a compensating container for a coolant in said cooling circuit arranged outside said cooling circuit in a parallel section connected in parallel with said cooling circuit and communicating with said cooling circuit;
a cooler with a coolant inlet integrated in said cooling circuit; and
a calming section connected upstream of said coolant inlet in a coolant flow direction for degassing and calming the coolant.
In other words, the novel system for cooling the stator and/or the rotor of a generator has a cooling circuit and a compensating container for a coolant flowing through the cooling circuit. The compensating container is arranged outside the cooling circuit and is connected to the cooling circuit by a line, whereby the compensating container is integrated into a parallel section connected in parallel with the cooling circuit. There is provided in the cooling circuit a calming section which serves for degassing and calming the coolant.
As set forth above, in the case of water-cooled generators a compensating container has frequently been arranged such that the entire coolant flows through it. This requires a compensating container of very large dimensions. Such a compensating container is a substantial cost factor. In the case of the present design, the compensating container is removed from the cooling circuit and integrated into a parallel section with respect to the cooling circuit. As a result, coolant flowing in the parallel section flows continuously through the compensating container. This affords the advantage, in particular, that the coolant in the compensating container does not stagnate. Stagnation of the coolant makes the latter more conductive with time, which can lead to insulation problems. With continuous through-flow, insulation problems that can be caused by stagnation are avoided.
The invention is based on the finding that, in the case of a parallel connection of the compensating container, the coolant is degassed only incompletely, since only a small part of the coolant flows through the compensating container and can be degassed there. In order to ensure extensive degassing, a calming section is arranged in the cooling circuit. Such a calming section may be e.g. simply a line connected in parallel with the cooling circuit. In such a calming section, the coolant flows more slowly and can degas. The parallel section in which the compensating container is arranged preferably branches off from said calming section. The main stream of the coolant flows through the latter, thereby achieving effective degassing of the coolant.
The compensating container preferably holds between 50 and 800 l (liter), in particular between 100 and 300 l. It is also preferably possible to guide a primary coolant flow through the cooling circuit and to guide a secondary coolant flow through the parallel section, the primary coolant flow being larger by a factor of 10 to 100, in particular by a factor of 50 to 200, than the secondary coolant flow. The primary coolant flow is preferably between 10 and 100 m
3
/h, in particular between 20 and 40 m
3
/h. The secondary coolant flow is preferably between 10 and 500 l/h, in particular between 100 and 250 l/h.
The compensating container is preferably connected to a discharge line which serves to discharge surplus coolant from the cooling circuit. It is thereby possible for surplus coolant to be discharged simply via a discharge line, whereas previously there was a need to provide an overpressure valve.
It is further preferred for the discharge line to have a U-shaped bend in the region of which a gas outlet opening is arranged such that upon overshooting of a limiting gas pressure in the compensating container gas can be discharged from the compensating container via the gas outlet opening. An overpressure valve can thereby be eliminated. The coolant level can preferably be monitored via a sight glass.
In accordance with an additional feature of the invention, the compensating container is positioned separately from the generator. The compensating container therefore does not form a structural unit with the generator. Such an embodiment is possible owing to the compensating container of smaller dimensions which is arranged outside the cooling circuit. In particular, this results in the advantage that the compensating container does not have to be provided with any expensive vibration damping. Such vibration damping is required when, as previously, the compensating container forms a structural unit with the generator, that is to say, for example, is arranged on the generator. The compensating container is thereby exposed to the vibrations which are caused by the generator during operation.
In accordance with again an additional feature of the invention, there is integrated a cooler with a coolant inlet in the cooling circuit, the calming section being connected upstream of the coolant inlet. It is preferred to provide two coolers whose coolant inlets are connect
Adelmann Werner
Becher Kurt
Eickelbeck Uwe
Emshoff Horst-Werner
Fischer Rainer
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
Tamai Karl
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