Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1991-04-12
1992-09-01
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 57, 310 64, 415175, 415176, 417370, H02K 9197
Patent
active
051441772
DESCRIPTION:
BRIEF SUMMARY
The heat developed in canned motors due to power loss is conventionally removed by a fluid stream which is conducted through the rotor chamber. The fluid stream is either branched off from the stream being conveyed by the centrifugal pump or is generated by an impeller provided for this purpose.
If the fluid conducted through the rotor chamber is explosive, it is necessary to provide safeguards which are prescribed by relevant codes. Above all, explosion protection clearances are to be arranged in the flow path of the fluid conducted through the rotor chamber.
An electric, submersible pump aggregate for containers with explosive or other dangerous fluids is disclosed in the German Offenlegungsschrift 2 006 681 and has a winding which is immersed in the fluid being conveyed. Overheating of the electric motor is prevented by maintaining fluid circulation in the electric motor during pump operation. To achieve complete sealing of the electric, submersible pump aggregate from the surroundings, the wires of the winding of the electric motor are provided with a coating resistant to the fluid being conveyed and are extended to such a degree that their ends can pass through seals to a junction box externally of the container. Since the container is an integral part of the protective measure, such measure can be used only for a submersible pump disposed in a container.
Another known safety measure is the encapsulation of the stator chamber so as to be pressure-resistant. In view of attempts to increase safety, and in view of distinct regulations relating to auxiliary protection, it is necessary to additionally monitor the rotor chamber during operation when the above-mentioned measures are put into effect.
When a fluid not originally intended for this purpose is conveyed through a canned motor, several problems arise aside from the possibility that this fluid is not well-suited for cooling. If this fluid contains solids, for example, fouling, obstruction of clearances, increased wear and other undesired consequences can occur. The disposition of filtering devices before the rotor chamber of the canned motor often only alleviates this problem temporarily. Since inadequate monitoring and maintenance of the filtering devices can cause blockage of the fluid flow, there is a danger here that the canned motor will receive an insufficient supply of cooling fluid. Inasmuch as the canned motor requires a continuous cooling stream, such a shortage will lead to failure of the canned motor within a short period.
To counteract the danger that, due to continuous passage of the fluid being conveyed, solid particles will enter the electric motor, the Belgian patent application 649 719 suggests a procedure in which the electric motor is filled with the fluid being conveyed one time and circulation between the pump chamber and motor chamber is then discontinued. However, since the canned motor pump proposed here is to be used mainly for the conveying of hot water, no additional measures for cooling or explosion protection are provided.
A danger exists for canned motors used as a drive for centrifugal pumps serving to convey explosive fluids, fluids which readily liberate gas or fluids near their boiling point. The conveyed fluid admitted into the rotor chamber from the pressure side of the centrifugal pump is progressively expanded and heated on its way through the rotor chamber before flowing off to the suction side of the centrifugal pump. There is the danger that the fluid will vaporize or liberate gas and that the flash point will be exceeded. This can lead to dry operation of the bearings and failure of the aggregate.
It is an object of the invention to provide a canned motor which has a pressure-resistant casing and which, for cooling of the rotor chamber, does not require passage of the fluid in contact with the driven machine.
According to the invention, the object set forth is achieved by a heat-exchanger which is disposed in the rotor chamber of the canned motor and has a fluid from externally of the rotor chamber flowing
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patent: 5039284 (1991-08-01), Talaski
patent: 5055006 (1991-08-01), Kobayashi et al.
Kontler Peter K.
KSB Aktiengesellschaft
Rebsch D. L.
Stephan Steven L.
LandOfFree
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