US3895335A

US3895335A - Series/parallel connected single phase power transformer

Info

Publication number: US3895335A
Application number: US475564A
Authority: US
Inventors: Abraham I Manimalethu
Original assignee: General Electric Co
Current assignee: ABB Inc USA
Priority date: 1974-06-03
Filing date: 1974-06-03
Publication date: 1975-07-15
Anticipated expiration: 1992-07-15
Also published as: CA1046600A

Abstract

An improved single phase power transformer having a three-legged magnetizable stacked core is disclosed. Two half-size outer core legs are parallel to and are spaced apart from a full-size central leg. Coil windings are located on the central leg of the transformer core only. High and low voltage windings are in an interleaved relationship, with the lowest potential portion of the high voltage coil winding adjacent the central leg of the transformer core. High voltage coil windings are connected in series and low voltage coil windings are connected in parallel.

Description

United States Patent [191 Manimalethu [451 July 15, 1975 1 SERIES/PARALLEL CONNECTED SINGLE PHASE POWER TRANSFORMER [75] Inventor: Abraham I. Manimalethu, Peru,

Mass.

[73] Assignee: General Electric Company, New

York, NY.

[22] Filed: June 3, 1974 [21] Appl. No.: 475,564

[52] US. Cl. 336/183 [51] Int. Cl. IIOIF 27/28 [58] Field of Search 336/180, 182, 183, 145, 336/146, 147, 170

[56] References Cited UNITED STATES PATENTS 1,652,911 12/1927 Sclater 336/183 1,979,096 10/1934 Cahall.... 336/183 X 2,680,218 6/1954 Keroes 336/183 X 2,713,667 7/1955 Schwennesen 336/183 FOREIGN PATENTS OR APPLICATIONS 925,599 3/1947 France 336/183 695,222 8/1953 United Kingdom 336/183 Primary Examiner-Thomas J. Kozma Attorney, Agent, or Firm-John J. Kelleher [57] ABSTRACT An improved single phase power transformer having a three-legged magnetizable stacked core is disclosed. Two half-size outer core legs are parallel to and are spaced apart from a full-size central leg. Coil windings are located on the central leg of the transformer core only. High and low voltage windings are in an interleaved relationship, with the lowest potential portion of the high voltage coil winding adjacent the central leg of the transformer core. High voltage coil windings are connected in series and low voltage coil windings are connected in parallel.

6 Claims, 3 Drawing Figures SERIES/PARALLEL CONNECTED SINGLE PHASE POWER TRANSFORMER BACKGROUND OF THE INVENTION My invention relates, in general, to electrical power transformers and more particularly to single phase power transformers of the three-legged stacked core type, said core having coil windings on one leg only.

Conventional power transformers of the single phase type have transformer cores of the two-legged or fourlegged stacked core type with coil windings on two legs of the transformer core. High voltage and low voltage windings are included in each coil of such transformers with coil windings subjected to the same working voltage being connected in parallel. These types of single phase power transformers have several inherent disadvantages. The major disadvantage in such transformer designs is that excessive amounts of core steel must be used. Another disadvantage is that such designs are relatively complex in that two separate coils are required and lengthy coil winding connections are required between coils. The aforementioned disadvantages results in a higher cost, less reliable transformer than one that does not have such disadvantages.

In order to avoid these and other disadvantages, it would be desirable to provide a single phase power transformer that would significantly reduce the amount of core steel required to fabricate sameas well as reduce costs and increase reliability.

Accordingly, it is an object of my invention to provide a single phase power transformer that is less costly to build than single phase power transformers utilizing a two-coil design and having two or more transformer core legs.

Another object of my invention is to provide a single phase power transformer that is more reliable than a single phase power transformer utilizing a two-coil design.

Still another object of my invention is to provide a single phase power transformer that will minimize the length of the connections required between coil windings.

SUMMARY OF THE INVENTION An improved single phase power transformer is disclosed that utilizes a single coil mounted on one leg of a three-legged transformer core of the stacked type. The present invention is a single phase power transformer that has a three-legged magnetizable stacked core with two half-size outer legs parallel to and spaced apart from a full-size central leg. Coil windings in the shape of hollow cylinders, concentric with each other, are positioned around the central leg of the transformer core only, such that the longitudinal central axes of the just mentioned coil windings are concentric with the longitudinal central axis of said central leg. High and low voltage windings are assembled such that they are in an interleaved relationship with each other, and the low potential winding portion of the high voltage coil windings is adjacent the central leg of the transformer core. The high voltage coil windings are connected in series and low voltage coil windings are connected in parallel.

The invention. which is sought to be protected, will be particularlypointed out and distinctly claimed in the claims appended thereto. However, it is believed that this invention and the manner in which its objects and vention.

advantages are obtained. as well as other objects and advantages thereof, will be more readily understood by reference to the following detailed description of the preferred embodiment thereof, particularly 'when considered in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings wherein like numerals are used to indicate like parts throughout. in FIG. 1 the most pertinent portions of single phase power transformer 12 of the present invention are depicted. Transformer core 14, of the stacked type, having

outer legs

16 and 18 and central leg 20 is shown supported by clamping structure 22. Transformer housing 24 enclosing transformer core 14 is shown in phantom. Coil 26, the only coil in transformer 12, is shown encircling central leg 20 of transformer core 14. Coil 26 consists of four coil windings which are best pictured in FIG. 2.

FIG. 2 is a horizontal cross-sectional view taken along the line 22 in FIG. I. In FIG. 2 cross-sections of

coil windings

28, 30, 32 and 34 of coil 26 are illustrated.

Coil windings

28, 30, 32 and 34 are in the shape of hollow cylinders, are generally concentric with each other and with the longitudinal axis of central leg mem ber 20. In addition, FIG. 2 shows a horizontal crosssectional view of

outer core legs

16 and 18 and central core leg 20. The cross-sectional area of each

outer core leg

16 and 18 is approximately equal to one-half the cross-sectional area of central leg 20.

Referring now to FIG. 3- where a shcematic diagram of the coil windings and coil connections of coil 26 is illustrated.

Coil windings

28, 30 32 and 34 are central coil leg 20 are in the same relative relationship as that depicted in FIG. 2. Coil winding 28 is a two terminal relatively high voltage, layer winding and is located immediately adjacent central coil leg 20. The circular cross-sectional shape of the hollow central portion of coil winding 28 conforms to the generally circular cross-sectional shape of central core leg 20. Coil winding 30 is a two terminal relatively low voltage, helical winding that is immediately adjacent to and external of coil winding 28. Coil winding 32 is a two terminal, relatively high voltage layer winding that is immediately adjacent and external of coil winding 30. Coil winding 34 is a two terminal, relatively low voltage layer winding that is immediately adjacent and external of coil winding 32.

The higher voltage coil windings of the transformer of the present invention are labeled wih the letter H and the lower voltage coil windings of the transformer of the present invention are labeled with the letter X.

One end of high voltage 32 is connected to one end of coil winding 28 in an electrical series-aiding circuit relationship by electrical connection 36. The remaining end of high voltage coil winding 32 is, for reference, designated H1 and is for connection to a high potential terminal. The remaining end of high voltage coil winding 28 is, for reference, labeled H2 and is for connec' tion to a low potential terminal. The terms high potential terminal and low potential terminal in this context mean high and low potential terminals with respect to one another.

One end of coil is connected to the end of coil 34 having the same polarity as coil 30 by electrical connection 38. The remaining end of coil 30 is connected to the remaining end of coil 34 by electrical connection 40. Electrical connection 38 is, for reference, labeled X1 and electrical connection 40, for reference, is labeled X2. X1 is for connection to a high potential terminal relative to X2 and X2 is for connection to a low potential terminal relative to X1.

What has been described is a single phase power transformer that can handle the same amount of power as previous designs but requires significantly less core steel, is less complex, more reliable and less costly to build than previous designs.

GENERAL CONSIDERATIONS l have discovered that if the reactance of a transformer coil is acccurately calculated it is possible to construct a single phase power transformer such as that described in the preferred embodiment. In such a transformer, current necessarily divides in a substantially uneven manner in the low voltage windings. If the reactance is not calculated to a fairly accurate degree, current in the low voltage windings will divide such that excessive current will pass through one of the low voltage windings causing the winding to fail. Computer programs have been available for several years for calculating the reactance of transformer coils to within three percent which is adequate for a transformer design'such as that described in the preferred embodiment.

The transformer of the type described herein is commonly known as a voltage step-up power transformer. However, my invention would apply equally well to a voltage step-down power transformer. In such a voltage step-up transformer the output voltage is significantly higher than the input voltage. Coil 26 of the transformer of the type described herein has four coil windings designated 28, 39, 32 and 34.

Coil windings

28 and 32 form the relatively high voltage winding portion of coil 26 and

coil windings

30 and 34 form the relatively low voltage winding portion of coil 26.

As previously stated, the letter H is associated with the high voltage windings and the letter X is associated with the low voltage windings. High voltage and low voltage in this sense is with respect to the high voltage and low voltage windings in the transformer coil. A high voltage or low voltage reference terminal within either of the high voltage windings or low voltage windings is terminology that is used herein to distinguish one end of a particular coil winding or windings from another and does not mean that the voltage at a particular terminal remains constant. XI and x2 are the high and low voltage reference terminals respectively, for the low voltage windings which are labeled X. H1 and H2 are the high and low voltage reference terminals respectively, for the high voltage windings which are labeled H.

High voltage and low voltge windings of the present invention are interleaved with respect to one another. That is to say a high voltage coil winding is located between low voltage coil windings and a low voltage coil winding is located between high voltage coil windings throughout the entire coil except for the innermost and outermost coil windings. High voltage and low voltage windings are never located immediately adjacent one another.

In the preferred embodiment coil windings of the layer type have been utilized. As a general. rule, layer type coil windings are used in very high voltage applications. However, in those applications where moderate values of voltage will be encountered, disc windings may be substituted for layer windings if such a substitution is compatible with the desired electrical characteristics.

The terms layer, helical and disc are used herein to describe particular well known types of coil windings and are among the most common types of transformer coil windings in present use in the transformer art. This being so. no description of these windings, other than their names, is included herein.

It sill be apparent to those skilled in the art from the foregoing description of my invention that various improvements and modifications may be made in it without departing from the true scope of the invention. Accordingly, it is my intention to encompass within the scope of the appended claims the true limits and spirit of my invention.

I claim:

I. In a single phase electrical power transformer of the type having a magnetizable three-legged stacked core, said core having a central leg and spacedapart outer legs parallel to said central leg, the crosssectional area of each of said outer legs being approximately one-half the cross-sectional area of said central leg, the improvement comprising:

a. a coil, including a plurality of hollow and generally cylindrical shaped alternating interleaved high voltage and low voltage windings, the longitudinal axes of said windings being generally concentric with each other and with the longitudinal axes of said central leg of said transformer core. having one of said high voltage windings immediately adjacent said central leg;

. means connecting said low voltage windings in parallel; and

c. means connecting said high voltage windings in series; sequentially from the innermost to the outermost high voltage windings.

2. A single phase electrical power transformer as defined in claim 1 wherein said coil consists of two high oltage windings and two low voltage windings.

3. A single phase electrical power transformer as defined in claim 2 wherein said high voltage windings are of the layer type, the low voltage windings between high voltage windings is of the helical type and the remaining low voltage winding is of the layer type.

4. A single phase electrical power transformer as defined in claim 2 wherein said high voltage windings are of the layer type. the low voltage windings between high voltage windings is of the helical type and the remaining low voltage winding is of the disc type.

5. A single phase electrical power transformer as defined in claim 2 wherein said high voltage windings are of the disc type. the low voltage winding between high 3 ,8 9 5 ,3 3 5 5 6 voltage windings of the helical type and the remaining of the disc type, the low voltage winding between the low voltage winding is of the layer type. high voltage windings is of the helical type and the re- 6. A single phase electrical power transformer as demaining low voltage winding is of the disc type. fined in claim 2 wherein said high voltage windings are LII

Claims

1. In a single phase electrical power transformer of the type having a magnetizable three-legged stacked core, said core having a central leg and spaced-apart outer legs parallel to said central leg, the cross-sectional area of each of said outer legs being approximately one-half the cross-sectional area of said central leg, the improvement comprising: a. a coil, including a plurality of hollow and generally cylindrical shaped alternating interleaved high voltage and low voltage windings, the longitudinal axes of said windings being generally concentric with each other and with the longitudinal axes of said central leg of said transformer core, having one of said high voltage windings immediately adjacent said central leg; b. means connecting said low voltage windings in parallel; and c. means connecting said high voltage windings in series, sequentially from the innermost to the outermost high voltage windings.

2. A single phase electrical power transformer as defined in claim 1 wherein said coil consists of two high voltage windings and two low voltage windings.

4. A single phase electrical power transformer as defined in claim 2 wherein said high voltage windings are of the layer type, the low voltage windings between high voltage windings is of the helical type and the remaining low voltage winding is of the disc type.

5. A single phase electrical power transformer as defined in claim 2 wherein said high voltage windings are of the disc type, the low voltage winding between high voltage windings of the helical type and the remaining low voltage winding is of the layer type.

6. A single phase electrical power transformer as defined in claim 2 wherein said high voltage windings are of the disc type, the low voltage winding between the high voltage windings is of the helical type and the remaining low voltage winding is of the disc type.