CN110534298B

CN110534298B - Cooling system for transformer

Info

Publication number: CN110534298B
Application number: CN201810517659.2A
Authority: CN
Inventors: 孙青军; 陆琼芳; 孙会刚
Original assignee: Hitachi Energy Switzerland AG
Current assignee: Hitachi Energy Co ltd
Priority date: 2018-05-25
Filing date: 2018-05-25
Publication date: 2022-12-16
Anticipated expiration: 2038-05-25
Also published as: CN110534298A

Abstract

The present application relates to a cooling system for a transformer having at least one coil winding. The cooling system includes at least one exhaust port to direct a flow stream of cooling air onto the coil windings. The discharge port may be a nozzle to increase the velocity of the flow stream. An air mover, such as a fan, is in fluid communication with each of the discharge ports to create an air flow therethrough. A signal generator operatively connected to the air mover is configured to vary a speed of the air mover between a maximum speed and a minimum speed such that a flow rate of air through each of the exhaust ports varies between the maximum speed and the minimum speed over time to cool the transformer.

Description

Cooling system for transformer

Technical Field

The present application relates generally to transformer cooling and more particularly, but not exclusively, to cooling transformers with directional variable speed fluid flow.

Background

A transformer is an electrical device that transfers electrical energy between two or more electrical circuits by electromagnetic induction. Transformers are used to step up or step down voltage in power applications. During operation, heat is generated within the transformer caused by electrical losses in the coil windings. Transformers must typically be passively and/or actively cooled, otherwise they eventually fail due to overheating (above a maximum threshold temperature). Dry-type transformers are air-cooled and, in some cases, include water-based liquid cooling in certain portions thereof. The liquid-based transformer is at least partially filled with a liquid dielectric material, such as oil or silicone oil, to cool the conductive coil windings. Some existing systems have various disadvantages with respect to certain applications. Therefore, there remains a need for further contributions to the art.

Disclosure of Invention

One embodiment of the present application is a transformer with a unique cooling system. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for a transformer and a cooling system that includes a variable speed cooling flow stream and/or a pulsed cooling flow stream directed to a predetermined region of the transformer. Other embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and drawings provided herein.

Drawings

FIG. 1 is a schematic diagram of a transformer and cooling system according to an exemplary embodiment of the present disclosure; and

FIG. 2 is a graph of cooling flow rate over time according to one exemplary control method for the cooling system of FIG. 1.

Detailed Description

For the purposes of promoting an understanding of the principles of the application, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the application is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the application as described herein are contemplated as would normally occur to one skilled in the art to which the application relates.

Referring to FIG. 1, in one non-limiting example of the present application, a transformer 10 is shown in schematic form. The transformer 10 may include a housing 12, the housing 12 at least partially enclosing components of the transformer 10. The transformer may include one or more coil windings 14. The coil winding 14 is a wire operable to raise or lower a voltage in the power system. The current flowing through the coil winding 14 generates a large amount of heat in the transformer. If the heat generated in the transformer 10 is not removed from the transformer 10, certain components within the transformer 10 may fail. The present disclosure includes an apparatus and method for efficiently removing heat from a transformer 10.

The transformer 10 may include a frame 16 to connect with the coil windings 14 and to hold the coil windings 14 in a fixed position. One or more conduit channels 18 may be associated with the frame 16 to direct the cooling fluid to a desired location.

A cooling system 20 may be operatively coupled to the transformer 10 to remove at least a portion of the heat generated within the coil windings 14 in the transformer 10. The cooling system 20 may include a variable flow system 22 and a heat exchanger system 24. The heat exchanger system 24 may include a heat exchanger 26, the heat exchanger 26 operable to transfer heat between two or more fluids. The heat exchanger 26 may include an inlet 28 for entry of a heat exchange cooling fluid and an outlet 30 for exit of the heat exchanger fluid. In one form, the heat exchange fluid may be a liquid water-based solution, and in other forms the heat exchange fluid may be a gas such as air. The heat exchange fluid may be cooled by various means such as ambient conduction, convection and/or radiant heat transfer means, and other forced cooling means. The fan 32 may draw a relatively hot air stream, represented by arrow 34, through an outlet port 36 in the housing 12 of the transformer 10 and direct a hot air stream, represented by arrow 38, through the heat exchanger 26. After the airflow is cooled by the heat exchanger 26, the cooled airflow, represented by arrows 39, is directed into the transformer 10 through an inlet port 40 of the housing 12. As will be readily appreciated by those skilled in the art, the cooling airflow 39 may be dispersed throughout the housing 12 and/or directed to defined locations within the housing 12 via internal ducts and/or passages (not shown).

Variable flow cooling system 22 includes a control system 50 operatively connected to a signal generator 52. The control system 50 may be programmed to cause the signal generator 52 to send a variable output frequency to the air mover 54. The air mover 54 may be of any type known to those skilled in the art, such as, for example and without limitation, a fan, a blower, and/or a compressor, among others. The variable output frequency causes the speed of the air mover 54 to vary between a maximum speed and a minimum speed. The maximum speed will provide the maximum airflow rate through the manifold 58 downstream of the air mover 54. The maximum airflow may be limited by the mechanical speed of the air mover 54 or by the design cooling mass flow rate requirement for providing a defined cooling requirement for the transformer 10. The minimum speed of the air mover 54 may be a lower speed as defined by heat transfer design requirements. In some forms, the minimum speed may include periodically shutting off the air mover 54, which causes the cooling fluid to temporarily stop in the variable flow system 22.

One or more flow exhaust ports 60 are operatively connected to the manifold 58 to receive the airflow from the manifold 58 and direct each discrete flow stream 62 to a defined location of the coil windings 14 or other high heat region in the transformer 10. In one aspect, one or more exhaust ports 60 may be associated with each coil winding 14 to direct one or more flow streams directly onto the coil windings 14. In one embodiment, the discharge port 60 is configured as a convergent nozzle to increase the velocity of the flow stream 62 discharged therefrom.

In some embodiments, variable flow system 22 may include an air mover 54 directly connected to each of one or more exhaust ports 60. In other embodiments, the variable flow system 22 may include a plurality of air movers 54, wherein each air mover 54 may be associated with one of the plurality of coil windings 14. In further embodiments, variable flow system 22 may include a separate air mover 54 connected to each exhaust port 60.

Referring now to FIG. 2, a graph 70 illustrating a cooling flow rate U (m/s) exiting the discharge port 60 as a function of time according to one exemplary control method is shown. Graph 70 shows an alternative sinusoidal control function that may be used to vary the cooling flow rate U exiting from the discharge port 60. In one form, the sine function may be defined as U (m/s) = U ₀ + A sin (Bt); where A is amplitude and B is frequency. It should be understood that the graph 70 represents only one control method that may be used with the variable flow system 22, and that the rate may be varied in any number of other control schemes that meet the heat transfer requirements of the transformer 10. The control system 50 may be programmed to cause the signal generator 52 to provide other output control signals to the air mover 54, such as a square signal output, a non-periodic signal output change, and/or a pulsed (on/off) output.

Experimental and simulation analysis results show that varying the flow rate of the cooling flow stream 62 exiting the discharge port 60 may increase the heat transfer efficiency of the cooling system 20. When the velocity of the cooling flow stream 62 is constant (the velocity does not change over time), a stable boundary layer is formed between the component and the cooling flow stream 62. As known to those skilled in the art, the stable boundary layer has a relatively large thickness, which reduces the effective heat transfer coefficient of the cooling fluid. When the rate of the cooling flow stream changes in amplitude and/or frequency, the boundary layer will be unstable and the resulting thinner boundary layer will have an increased heat transfer coefficient, thereby providing increased heat transfer efficiency. It has been determined that the heat transfer coefficient of a cooling fluid flow stream having a variable flow rate or pulsed flow can be increased by up to 47% over a steady cooling flow stream. Furthermore, it has been found that providing a rectangular output with a step change in flow can increase the heat transfer rate by up to 30% when the frequency of the on/off function is about 40Hz (cycles/second) or higher.

In one aspect, the present disclosure includes a transformer cooling system comprising: a transformer having a conductive coil winding; a blower for generating a flow of cooling fluid; a discharge port in fluid communication with the blower; and a controller operatively connected to the blower, the controller being operable to produce a change in flow rate of the cooling fluid through the discharge port.

In a refinement, the transformer cooling system comprises: an exhaust port directing the cooling fluid directly onto the electrically conductive coil; wherein the discharge port is a nozzle; wherein the controller comprises a signal generator; wherein the signal generator varies the speed of the blower; wherein the blower is cycled on and off periodically to produce a pulsed flow; wherein the cooling fluid comprises air; wherein the transformer comprises a plurality of conductive coil windings; and a plurality of exhaust ports operable to direct cooling fluid onto each of the electrically conductive coil windings; also included is a heat exchanger having a heat exchange fluid passing therethrough; wherein the heat exchange fluid cools air circulating between the transformer and the heat exchanger; and further includes a heat exchanger fan operable to move air across the heat exchanger.

Another aspect of the present disclosure includes a transformer, comprising: a plurality of coil windings; a nozzle associated with each coil winding; a manifold operatively connected to each nozzle; an air mover in fluid communication with the manifold; a signal generator operatively connected to the air mover, the signal generator configured to vary the speed of the air mover between a maximum speed and a minimum speed such that the flow rate of air through each nozzle is periodically varied between a maximum rate and a minimum rate to cool the transformer.

In a refinement, the transformer comprises: the minimum velocity of flow through each nozzle is zero; wherein the signal generator is operable to output one of a sine wave, square wave and/or pulsed wave signal to the air mover; wherein the air mover is one of a fan, blower, or compressor; a heat exchanger fluidly coupled between the heat exchanger fan and the transformer; and wherein the heat exchange fan circulates air from the transformer through the heat exchanger and back to the transformer.

Another aspect of the present disclosure includes a method for cooling a transformer, comprising: directing a flow stream of cooling air onto a portion of a coil winding of a transformer; and periodically varying the flow of cooling air between the maximum rate and the minimum rate.

In a refinement of the method, the directing includes increasing a velocity of the flow through the nozzle; wherein the change in flow rate is controlled by a signal generator operatively connected to the air mover; wherein the change is one of a sinusoidal function and a square wave function; wherein the minimum rate is zero; and cooling the transformer with a heat exchanger system.

Another aspect of the present disclosure includes a transformer cooling system comprising: a transformer comprising a conductive coil winding; an air mover in fluid communication with the transformer; an exhaust port connected to the air mover, the exhaust port configured to direct airflow onto the coil windings; and a controller configured to send a control signal to the air mover, wherein the control signal periodically varies the speed of the air mover between a maximum speed and a minimum speed.

In a refinement, the transformer comprises: a minimum speed of zero; a plurality of exhaust ports configured to direct airflow onto the plurality of coil windings; and a signal generator configured to provide at least one of a sine wave output, a square wave output, and/or a pulsed output to the air mover.

While the application has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the application are desired to be protected. It should be understood that while the use of words such as preferred, preferably, preferred or more preferred in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the application, that scope being defined by the claims that follow. In reading the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used, there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used, the item can include a portion of the item and/or the entire item unless specifically stated to the contrary.

Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.

Claims

1. A transformer cooling system comprising:

a transformer having a conductive coil winding, an outlet port, and an inlet port;

a variable flow system, the variable flow system comprising:

a blower for generating a flow of cooling fluid;

an exhaust port in fluid communication with the blower and operable for directing cooling fluid to a defined location of the electrically conductive coil windings or other high heat location in the transformer; and

a controller operatively connected to the blower, the controller being operable to produce a periodic change in the flow rate of cooling fluid through the discharge port between a maximum rate and a minimum rate; and a heat exchanger system, the heat exchanger system comprising:

a heat exchanger fan; and

a heat exchanger for the heat-exchange of the heat-exchange medium,

wherein the heat exchanger fan absorbs air from the transformer through the outlet port and directs the air through the heat exchanger and back into the transformer through the inlet port.

2. The transformer cooling system of claim 1, wherein the exhaust port directs cooling fluid directly onto the electrically conductive coil windings.

3. The transformer cooling system of claim 1, wherein the drain port is a nozzle.

4. The transformer cooling system of claim 1, wherein the controller comprises a signal generator.

5. The transformer cooling system of claim 4 wherein the signal generator varies the speed of the blower.

6. The transformer cooling system of claim 1 wherein the blower is cycled on and off periodically to create a pulsed flow.

7. The transformer cooling system of claim 1, wherein the cooling fluid comprises air.

8. The transformer cooling system of claim 1, wherein the transformer comprises a plurality of conductive coil windings.

9. The transformer cooling system according to claim 8, further comprising a plurality of exhaust ports operable to direct cooling fluid onto each of the conductive coil windings.

10. The transformer cooling system of claim 9, further comprising a manifold in fluid communication with the blower and the plurality of exhaust ports.

11. The transformer cooling system of claim 1, wherein the heat exchanger has a heat exchange fluid passing therethrough.

12. The transformer cooling system of claim 11, wherein the heat exchange fluid cools air circulating between the transformer and the heat exchanger.

13. A transformer, comprising:

a plurality of coil windings;

a housing having an outlet port and an inlet port;

a variable flow system, the variable flow system comprising:

a nozzle associated with each of the coil windings to operatively direct cooling fluid to a defined location of the electrically conductive coil windings or other high heat location in the transformer;

a manifold operatively connected to each nozzle;

an air mover in fluid communication with the manifold; and

a signal generator operatively connected to the air mover, the signal generator configured to vary the speed of the air mover between a maximum speed and a minimum speed such that the flow rate of air through each of the nozzles periodically varies between a maximum rate and a minimum rate to cool the transformer; a heat exchanger system, the heat exchanger system comprising:

a heat exchanger fan; and

a heat exchanger for the heat-exchange of the heat-exchange medium,

wherein the heat exchanger fan absorbs air from the housing through the outlet port, and

directing the air through the heat exchanger and back into the housing through the inlet port.

14. The transformer of claim 13, wherein the minimum velocity of flow through each nozzle is zero.

15. The transformer of claim 13, wherein the signal generator is operable to output one of a sine wave, square wave and/or pulsed wave signal to the air mover.

16. The transformer of claim 13, wherein the air mover is one of a fan, a blower, or a compressor.

17. The transformer of claim 13, wherein the heat exchanger is fluidly coupled between a heat exchanger fan and the transformer.

18. The transformer of claim 17, wherein the heat exchanger fan circulates air from the transformer through the heat exchanger and back to the transformer.

19. A method for cooling a transformer, comprising:

operably directing a flow stream of cooling air by an air mover through an exhaust port onto a portion of a coil winding of the transformer;

periodically varying the flow of cooling air between a maximum rate and a minimum rate; and

air from the transformer is drawn through the outlet port of the transformer by a heat exchanger fan of the heat exchanger and directed through the heat exchanger and back into the transformer through the inlet port of the transformer.

20. The method of claim 19, wherein the discharge port is a nozzle, and wherein the directing comprises: increasing the rate of flow through the nozzle.

21. The method of claim 19 wherein the change in flow rate is controlled by a signal generator operatively connected to the air mover.

22. The method of claim 19, wherein the change is one of a sinusoidal function and a square wave function.

23. The method of claim 19, wherein the minimum rate is zero.

24. A transformer cooling system comprising:

a transformer comprising a conductive coil winding, an outlet port, and an inlet port;

a variable flow system, the variable flow system comprising:

an air mover in fluid communication with the transformer;

an exhaust port connected to the air mover, the exhaust port configured to operably direct airflow onto the electrically conductive coil winding; and

a controller configured to send a control signal to the air mover, wherein the control signal periodically varies a speed of the air mover between a maximum speed and a minimum speed; and

a heat exchanger system, the heat exchanger system comprising:

a heat exchanger fan; and

a heat exchanger for the heat-exchange of the heat-exchange medium,

25. The transformer cooling system of claim 24, wherein the minimum speed is zero.

26. The transformer cooling system according to claim 24, further comprising a plurality of exhaust ports configured to direct airflow onto a plurality of coil windings.

27. The transformer cooling system of claim 24, further comprising a signal generator configured to provide at least one of a sine wave output, a square wave output, and/or a pulsed output to the air mover.