Superconducting Power Transformer Research Articles

Some considerations on superconducting transformers from a design-point of view

Superconducting transformers are now being manufactured, designed using prototypes and testing. However, few studies have been made on the characteristics of superconducting transformers from a design point of view. In this paper, the authors have designed a superconducting transformer by changing the principal design, such as volts per turn or leakage impedances, and investigated their effects on the principal characteristics of power transformers such as size, weight, loss, and cost. Comparing the results with those obtained for conventional transformers, features peculiar to the design of superconducting power transformers are made clear.

Conceptual design of air-core superconducting power transformer for cable transmission system

The air-core superconducting transformer, which has a large magnetizing current, has been proposed as a power transformer that has the function of a shunt reactor. In this paper, the basic design procedure for the air-core superconducting transformer is presented. By using this procedure, a 500//spl radic/(3 kV)-66//spl radic/(3 kV)-300 MVA single phase air-core transformer is designed for a model cable transmission system. Then, the performance of this transformer in the model cable transmission system is analyzed, and it is confirmed that the air-core superconducting transformer can function as a shunt reactor in addition to the principal function as a power transformer.

無鉄心形超電導変圧器の磁界および電磁力の解析

無鉄心形超電導変圧器の磁界および電磁力の解析

Comparison between superconducting and conventional power transformers considering auxiliary facilities

Due to the remarkable progress of AC superconducting wires, superconducting power transformers, which have the advantages of the reduction of size, weight and loss, are being investigated actively. However, considering the auxiliary facilities such as an outer cryogenic system, these advantages of the superconducting transformer over the conventional transformer are unclear. Thus, in this paper, a comparison of the size, weight and loss of superconducting transformers including auxiliary facilities with those of conventional transformers having the same output volt-ampere capacity is made. From the results of the comparison, the advantages of superconducting transformers are clarified. >

Characteristics analysis of superconducting power transformer without iron core

AbstractWith the progress of superconducting wires for ac power use, research on superconducting power transformers is increasing. These transformers can be divided into two types: the iron‐core type [1, 2]; and the air‐core type [3–9]. The latter type has such advantages as absence of iron losses and magnetic saturation, and greater possibility of reduction of size and weight. However, the air‐core transformer has a large magnetizing current due to the absence of iron core. Hence, research has been carried out on the possibility of using the air‐core transformer also as a shunt reactor in a power transmission system. However, the operating characteristics of the air‐core transformer, such as voltage regulation and reactance voltage, are not clear at present.In this paper, the equivalent circuit without losses is proposed first. Since this equivalent circuit is expressed by means of the magnetic coupling factor and self‐inductances of windings, the effect of these parameters on the transformer characteristics can easily be investigated. Then, based on this equivalent circuit, the per‐unit expressions for the air‐core transformer characteristics are derived and the characteristics are analyzed in detail. The validity of the theoretical results are confirmed by experimental results obtained by the use of an experimental superconducting transformer.

Volt-ampere rating of air-core superconducting power transformers

The authors point out that air-core superconducting power transformers have the potential of serving not only as power transformers but also as shunt reactors when used in power transmission systems having large capacitances. Here, the rated primary volt-amperes, volt-amperes as a shunt reactor, and related quantities are analyzed and their relations to the magnetic coupling factor and magnetizing reactance of the transformer are clarified. >

Characteristics Analysis of Superconducting Power Transformer without Iron Core.

With the progress of superconducting wires for ac power use, research on superconducting power transformers is increasing. These transformers can be divided into two types: the iron-core type [1, 2]; and the air-core type [3–9]. The latter type has such advantages as absence of iron losses and magnetic saturation, and greater possibility of reduction of size and weight. However, the air-core transformer has a large magnetizing current due to the absence of iron core. Hence, research has been carried out on the possibility of using the air-core transformer also as a shunt reactor in a power transmission system. However, the operating characteristics of the air-core transformer, such as voltage regulation and reactance voltage, are not clear at present. In this paper, the equivalent circuit without losses is proposed first. Since this equivalent circuit is expressed by means of the magnetic coupling factor and self-inductances of windings, the effect of these parameters on the transformer characteristics can easily be investigated. Then, based on this equivalent circuit, the per-unit expressions for the air-core transformer characteristics are derived and the characteristics are analyzed in detail. The validity of the theoretical results are confirmed by experimental results obtained by the use of an experimental superconducting transformer.

Basic characteristics of superconducting power transformer without iron core.

Basic characteristics of superconducting power transformer without iron core.

Finite element analysis of transient phenomena in four-wound type of superconducting power transformer

The FEM (finite-element method) was used to design the magnetic circuit of a superconducting four-winding power transformer and in the computer simulation of a sudden short-circuit state and other transient characteristics. Although some estimation errors occurred after quench, it is found that the quantitative agreement between the experimental results and theoretical ones in normal operations is fairly good. The theoretical approach suggests the propagation mechanism of the quench phenomena in the superconducting windings.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Superconducting power transformer with an auxiliary winding only on the lower‐voltage side and its behavior at line faults

Superconducting power transformer with an auxiliary winding only on the lower‐voltage side and its behavior at line faults

Preliminary tests on a superconducting power transformer

Test results for a 50-Hz single-phase power superconducting transformer are presented and discussed. The near-ambient-temperature iron core, of conventional shape, is situated in a fiber-glass reinforced-composite inner vessel which is vacuum insulated from the He bath. The iron core is cooled by an inner channel. Inter-leaved low-voltage and high-voltage windings are wound around the inner vessel by halved formers and cooled by natural convection in a 4.21 K He bath. The tests demonstrated construction feasibility (showing considerable weight reduction compared with nonsuperconducting designs); increased efficiency for power levels of about 1 MVA; and fault current strongly limited by the high value of conductor matrix resistivity. >

Superconducting power transformer with an auxiliary winding only in low voltage side and its behavior at line faults.

Superconducting power transformer with an auxiliary winding only in low voltage side and its behavior at line faults.

A feasibility study on a superconducting power transformer

The feasibility of a UHV superconducting transformer(SCT) in an electric power system is studied. A 1100/550kV, 1750MVA SCT is conceptually designed, which has windings of ultra-fine filament superconducting wire and an amorphous alloy core. The total loss of the SCT is calculated to be about 300kW at room temperature assuming that the refrigerator efficiency is 1/500. In this calculation, the heat leak loss, stray loss, etc. are included. This value of the total loss is about 20 - 25% of that of conventional transformers.

The feasibility of superconducting power transformers

The feasibility of making a 600 MVA 400 kV power transformer with superconductive windings to save I 2R losses is discussed, and the economic incentive assessed. Despite the radical change in concept, the transformer would be roughly the same size, shape, and weight as a conventional one. The tank would be vacuum tight, and the whole evacuated. This vacuum would insulate the windings electrically and thermally. Each winding would comprise two separate single layers of rectangular copper tube coated with superconductor and cooled internally with fluid helium at about 5 K. The extra cost of such a transformer is uncertain, but will probably exceed the saving in copper losses.

Physical limitations on the size of superconducting power transformers

The volume of a superconducting transformer is calculated by investigating the behaviour of an idealised, lossfree, interleaved transformer. Because of the limitation of leakage magnetic fields with superconducting windings, it is found that the volume is large compared with a conventional transformer of the same power rating. It is shown how the volume of an idealised transformer can be reduced. When account is taken of the additional factors involved in designing a real superconducting transformer, it seems very probable that its size will be so much larger than that of an equivalent conventional transformer as to be unacceptable.

Superconducting power transformers — A feasibility study

Increased efficiency is the main benefit of superconductivity. Some power is needed to operate the refrigerator but it is extremely small. Reduction in transformer size is also important. Other advantages include an improvement in power factor, extended life, and automatic limiting of short circuits.