Patent Application
20120086533
The present invention relates generally to transformers such as those used in power conversion systems. More particularly, the present invention relates to multi-phase transformers winding placement with different number of air ducts.
Multi-phase transformers such as 9 phase transformers, are configured to convert a 3-phase AC input power to a multi-phase (e.g. 9 phase) AC output power. Such transformers are typically designed to provide a desired output AC power. The output AC power generated by the transformer may be rectified or filtered before being supplied to a load.
Typically, a 9 phase transformer includes 3 coils constructed on a laminated core. Each coil is formed of several windings. For example, in many 9 phase transformers, each coil is formed of five separate windings. Thus, the 9 phase transformer is typically formed using 15 windings connected in series.
During operation, leakage inductance is present in each winding of the coil. The leakage inductance in each coil often is typically unequal due to placement of the windings and air ducts. Such unbalanced leakage inductance causes an increase in the total harmonic distortion in the input power.
One technique often employed to reduce leakage inductance is winding the coil in different layers, each layer including several windings. For example, for a coil including five separate windings, one layer may be formed using first two windings and a portion of the third winding and a second layer may be formed with the other portion of the third winding and the remaining two windings. However, constructing the coil in multiple layers causes excessive heat generation that can eventually damage the transformer if the winding size is not properly selected.
To reduce the cost or reduce the winding temperature, Cooling ducts are typically employed to dissipate the heat generated by the transformer. However, there is a constraint on the number of cooling ducts that can be accommodated in the transformer as an increased number of cooling ducts will increase the size and the cost of the system as well. Therefore, there is a need to design a multi-phase transformer with an effective cooling system.
Briefly, according to one embodiment of the invention, a transformer for converting 3 phase AC power to 9 phase AC power is provided. The transformer comprises a laminated core, first, second and third coils constructed on the laminated core, each coil including several windings. Cooling ducts are provided in each coil, wherein at least one cooling duct is disposed between the laminated core and an adjacent winding of the respective coil. The transformer further includes first, second and third input terminals each linked to the first, second and third coils, and configured to receive a first, second and third phases of input AC power, and first through ninth output terminals linkable to first through ninth output power lines.
In another embodiment, a transformer for converting 3 phase AC power to 9 phase AC power is provided. The transformer includes a laminated core and a first, second and third coils constructed on the laminated core. Each coil forms five separate windings including first, second, third, fourth and fifth windings. The transformer further includes a plurality of cooling ducts in each coil, wherein at least one cooling duct is disposed between the laminated core and an adjacent winding of the respective coil. The transformer further includes first, second and third input terminals each linked to the first, second and third coils, and configured to receive a first, second and third phases of input AC power and first through ninth output terminals linkable to first through ninth output power lines. The first, second and third input terminals and the first through ninth output terminals are disposed on an outer surface of the transformer.
In another embodiment, a method for making a transformer for converting 3 phase AC power to 9 phase AC power is provided. The method comprises constructing first, second and third coils around a laminated core, each coil having a plurality of windings coupled together to form a transformer. The method further includes providing a plurality of cooling ducts for each coil with at least one cooling duct disposed between the laminated core and an adjacent winding of the respective coil. The method further includes providing 3 input terminals and 9 output terminals on an outer surface of the transformer.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Turning now to the drawings, and referring first to
It should be noted that references in this specification to “one embodiment”, “an embodiment”, “an exemplary embodiment”, indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
The power source 12 is configured to generate or provide 3 phase AC power, and in many cases may comprise the utility grid. The 3 phase AC power may be provided to various electrical devices such as to the transformer 20. Moreover, the transformer 20 is coupled to the power source 12 and receives 3 phase AC power. The 3 phase AC power is provided to 3 separate input terminals 14, 16 and 18 as first, second and third phases. In this exemplary embodiment, the transformer 20 is configured to convert 3 phase AC power to 9 phase AC output power. In the illustrated embodiment, the output power is provided to the rectifier 22 via 9 output lines 21-A through 21-I, respectively.
Moreover, the rectifier 22 is configured to convert the 9 phase output AC power to corresponding DC voltage across a DC bus (not shown). In one embodiment, the rectifier 22 includes a switch-based bridge including two switches (not shown) for each AC voltage phase which are each linked to the DC bus. The switches are alternately opened and closed in a timed fashion that causes rectification of the 9 phase AC output power generated by the transformer 20.
The rectified output DC power may be provided to the load or may be used for various downstream circuits (e.g., inverters, choppers, converters). Other types and topologies of rectifiers, and indeed other uses for the 9 phase output may be employed. As described above, the transformer 20 is configured to convert 3 phase AC power to 9 phase AC power. The components used to construct the transformer 20 are described in further detail below with reference to
The poles 26, 28 and 30 pass through first, second and third coils 32, 34 and 36 respectively. In one embodiment, each coil (e.g., 32, 34 and 36) includes several windings coupled together in series. Further, each coil includes several cooling ducts represented generally by reference numeral 35, disposed between the windings. In one embodiment, each coil has first, second, third, fourth and fifth windings. Each winding may be constructed using a single winding specific wire.
Alternatively, several series windings may be constructed using a single wire or all of the windings may be constructed using a single wire. In one embodiment, all of the windings have a similar construction, the distinction being primarily in the number of turns that are included in each winding. The manner in which the windings are linked to form the transformer 20 is described in further detail below.
As can be seen in
The input terminals 14, 16 and 18 are configured to receive a first, second and third phases or power, represented generally by the letters A, B and C. The 3 input terminals are each coupled to first, second and third coils respectively. More specifically, the input terminal 14 is provided between winding 80 and winding 52. Similarly, input terminal 16 is provided between winding 66 and winding 72, and input terminal 18 is provided between winding 60 and winding 68. In alternate embodiments, the input terminals may be provided at positions 14″, 16″ and 18″ as shown in
The transformer 20 further includes 9 output terminals 21-A through 21-I as shown. The first output terminal 21-A is positioned at a node 81 between the first winding 52 and second winding 54 of the first coil 32. The second output terminal 21-B is positioned at a node 82 between first winding 62 and second winding 64 of the second coil 34. The third output terminal 21-C is positioned at a node 83 between the second winding 64 and third winding 66 of the second coil 34.
The fourth output terminal 21-D is positioned at a node 84 between the first winding 72 and second winding 74 of the third coil 36. The fifth output terminal 21-E is positioned at a node 85 between the third winding 56 and fourth winding 58 of the first coil 32. The sixth output terminal 21-F is positioned at a node 86 between the fourth winding 58 and fifth winding 60 of the first coil 32.
The seventh output terminal 21-G is positioned at a node 87 between the fourth winding 68 and fifth winding 70 of the second coil 34. The eighth output terminal 21-H is positioned at a node 88 between the third winding 76 and fourth winding 78 of the third coil 36. The ninth output terminal 21-I is positioned at a node 89 between the fourth winding 78 and fifth winding 80 of the third coil 36.
The transformer 20 includes several cooling ducts disposed between the windings of each coil. In one embodiment, each coil of the transformer 20 includes at least five cooling ducts on each side of the coil. The cooling ducts disposed between the windings of the coil. The manner in which the cooling ducts are disposed within the coil is described in further detail below.
It may be noted that winding 52 includes two portions that are generally represented by 52-A and 52-B. Similarly, winding 54 includes two portions and is generally represented by 54-A and 54-B and winding 58 includes two portions and is generally represented by 58-A and 58-B. Further, an insulating layer 95 is disposed between the windings as shown.
As illustrated, a cooling duct 92 is disposed between the laminated core 24 and portion 52-A of the winding 52. Further, a cooling duct 94 is disposed between the portions 52-A and 54-A of the windings 52 and 54 respectively. Similarly, a cooling duct 96 is disposed between the winding 56 and a first portion of the winding 58-A. Moreover, a cooling duct 98 is disposed between portions 58-A and 58-B of the winding 58 and a cooling duct 100 is disposed between portions 54-B and 52-B of the windings 54 and 52 respectively.
Here, the input terminals 14, 16 and 18 are positioned on the top side 90 of the transformer 20. Similarly, the output terminals 21-A through 21-I are also positioned on the top side 90 of transformer 20. As can be seen, all the input terminals 14, 16 and 18 and the output terminals 21-A through 21-I are disposed on an outer surface of the transformer.
In the illustrated embodiment, the winding 52 includes two portions and is generally represented by 52-A and 52-B and the winding 58 includes two portions and is generally represented by 58-A and 58-B. A cooling duct 102 is disposed between the laminated core 24 and portion 58-A of the winding 58. Further, a cooling duct 104 is disposed between winding 58-A and winding 56. A cooling duct 106 is disposed between winding 56 and winding 52-A. Moreover, a cooling duct 108 is disposed between portions 52-A and 52-B of the winding 52 and a cooling duct 110 is disposed between the winding 58-B and winding 60.
Again, as with the embodiment of
A cooling duct 112 is disposed between the laminated core 24 and portion 58-A of the winding 58. Further, a cooling duct 114 is disposed between winding 58-A and the winding 56. A cooling duct 116 is disposed between the winding 56 and portion 52-A of the winding 52 and a cooling duct 118 is disposed between windings 52-A and 52-B. Moreover, a cooling duct 120 is disposed between winding 52-B and winding 60 and a cooling duct 122 is disposed winding 60 and winding 58-B.
The input terminals 14, 16 and 18 are positioned on the top side 90 of transformer 20. Similarly, the output terminals 21-A through 21-I are also positioned on the top side 90 of transformer 20.
A cooling duct 126 is disposed between the laminated core 24 and winding 58-A and a cooling duct 128 is disposed between 58-A and winding 56. Further, a cooling duct 130 is disposed between winding 56 and winding 52-A and a cooling duct 132 is disposed between 52-A and winding 52-B. Moreover, a cooling duct 134 is disposed between 52-B and winding 58-B and a cooling duct 136 is disposed 58-B and winding 54. Cooling duct 138 is disposed winding 54 and winding 60.
The input terminals 14, 16 and 18 are positioned on the top side 90 of transformer 20. Similarly, the output terminals 21-A through 21-I are also positioned on the top side 90 of transformer 20
At step 144, a plurality of cooling ducts is provided for each coil. Specifically, at least one cooling duct is disposed between the laminated core and the first winding of the coil. In one embodiment, the cooling duct is an air gap. In one embodiment, each coil has at least 5 cooling ducts. In one embodiment, each coil has 7 cooling ducts.
At step 146, 3 input terminals and 9 output terminals are provided on an outer surface of the transformer. In one embodiment, the input and output terminals are provided on a top side of the transformer. In addition, the input terminals and output terminals are positioned adjacent to cooling ducts.
The above described invention has several advantages including minimizing the leakage inductance difference in windings of each coil. Also, the transformer is cooled efficiently since the cooling ducts are positioned adjacent to the core of the transformer. In addition, the input and output terminals positioned on an outer surface of the transformer allows easy interface with other systems.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
