Electricity: conductors and insulators – With fluids or vacuum – With cooling or fluid feeding – circulating or distributing
Reexamination Certificate
1999-07-22
2002-06-04
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
With fluids or vacuum
With cooling or fluid feeding, circulating or distributing
C174S015200
Reexamination Certificate
active
06399876
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to transformers, and more particularly to a system for cooling transformers.
BACKGROUND OF THE INVENTION
Transformers are used to transfer electric power between circuits that operate at different voltages. A simple model of a transformer consists of two insulated electrical windings, a primary and a secondary, coupled by a common magnetic circuit. When an alternating voltage is applied to the primary winding, an alternating current will flow to a load connected to the secondary winding.
Transformers generally operate near an efficiency of 98-99%. Any losses ordinarily arise from hysteresis and eddy current loss in the core, resistive loss in the windings, and circulating current loss in the structural parts due to proximity of heavy current leads. Although the total loss may be only 1% of the power transmitted, this may be equivalent to 10 MW on a large transformer.
Transformers must be designed to withstand the adverse effects resulting from high voltage and temperature. Well known in the field of cooling transformers, fluid filled transformers incorporate a cooling radiator and circulate a cooling fluid throughout a closed circulatory path formed between the connection of the transformer and the cooling radiator. Careful design is required to avoid overheating the windings which would cause premature aging of the insulation and lead to an electric breakdown in the windings. The choice of cooling methods will greatly determine the quality of the transformer.
Cooling of liquid filled transformers is the process by which the energy losses that are generated in the core and coil assembly are dissipated to the surrounding air. The losses, which appear in the form of heat, must be directed away from the windings to avoid premature deterioration of the insulation. The transfer of heat energy is accomplished through a combination of transfer processes. These processes are conduction, convection and radiation. Conduction is a heat transfer process where heat energy is transferred through a material by the passing of energy from one particle to the next without any mass motion in the material, i.e. a copper rod. Convection is a heat transfer process where heat energy is transferred from one place to another by actual motion of the medium, i.e. a liquid or gas. Radiation is a heat transfer process where heat energy is transferred from one place to another by magnetic waves or particles without any medium playing an active role, i.e. heat from the sun. The individual contributions of each heat transfer process must be added together to determine the total effective cooling for the transformer. The transformer designer can control the contribution of each parameter through the use of cooling ducts, oil column height, tank size and/or area exposed to the cooling air.
Transformers are usually quite large and generate great amounts of heat. Traditional methods of cooling transformers include fluid cooling or immersing the transformer in oil. Transformers cooled by oil immersion may be more efficient at cooling the transformer, however oil immersed transformers pose a risk to the environment through possible contamination resulting from spills during maintenance, repair or damage to the transformer oil tank.
The present invention is provided to solve these and other problems.
SUMMARY OF THE INVENTION
The present invention is a transformer apparatus and a method for cooling a transformer. According to one aspect of the invention, a transformer is provided having a plurality of cooling panels with each panel having an exterior end. A plate is positioned toward at least a portion of the exterior ends of the cooling panels, thus forming a flow path for increased velocity of air therein.
A second aspect of the present invention relates to a fluid cooled transformer having a plurality of cooling panels with each panel having an exterior end. A plate is positioned toward at least a portion of the exterior ends of the cooling panels, thus forming a flow path for increased velocity of air therein.
A third aspect of the present invention relates to a radiator for a transformer, the radiator having a plurality of cooling panels with each panel having an exterior end. A plate is positioned toward at least a portion of the exterior ends of the cooling panels forming a flow path for increased fluid velocity therein.
A fourth aspect of the present invention involves a fluid cooled transformer comprising a plurality of cooling panels with each panel having an exterior end. A plate is positioned toward at least a portion of the exterior ends of the panels for substantially enclosing a flow path between the exterior ends, thereby increasing the velocity of air therein.
A further aspect of the present invention involves a fluid cooled transformer comprising a plurality of cooling panels, each panel having an exterior end and a cooling plate extending therefrom. Positioning multiple panels adjacent each other forms a flow path between the plate and the adjacent cooling panels, thereby increasing the velocity of air therein. It is also contemplated by this invention that at least one cooling plate is attached to each cooling panel.
Another aspect of the present invention relates to fluid cooled transformers having a plurality of conduits fluidly connected perpendicularly to the cooling panels and also fluidly connected to the transformer.
Yet another aspect of the present invention involves a method of cooling a transformer having a plurality of cooling panels with each panel having an exterior end. The method of cooling comprises the steps of providing a plate and forming a flow path by positioning the plate toward at least a portion of the exterior ends for substantially enclosing the flow path between the cooling panels, thereby increasing the velocity of air traveling within the flow path.
It is also contemplated by this invention that the plates used to enclose a flow path are substantially solid.
Other advantages and aspects of the present invention will become apparent upon reading the following description of the drawings and detailed description of the invention.
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Femal Michael J.
Golden Larry I.
Mayo III William H.
Reichard Dean A.
Square D Company
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