CIRED Workshop - Lyon, 7>8 June 2010 

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AMORPHOUS MATERIALS AND ENERGY EFFICIENT

DISTRIBUTION TRANSFORMERS

Christophe ELLEAU 

EDF R&D – LME – France 

Christophe.Elleau@edf.fr 

 Malick MOUHAMAD Olivier GENIN Bertrand JARRY 

 EDF R&D – LME – France ERDF / DPI – France ERDF / DFI - France 

 Malick.Mouhamad@edf.fr Olivier.Genin@erdfdistribution.fr Bertrand.Jarry@erdfdistribution.fr 

ABSTRACT 

This paper deals with EDF Research and Development 

work for ERDF needs in terms of energy efficiency, 

focused on Amorphous Metal Distribution Transformers 

(AMDT). Investigations are carried out on the amorphous 

material itself including studies of characteristics such as 

aging, chemical compatibility and properties evaluation. 

EDF R&D contributes to defining the next amorphous 

transformers to match the strict ERDF requirements for 

withstanding short circuit and for noise level limitation. 

Technical proposals of manufacturers will be analysed 

next. ERDF plans to make field investigations with the 

prototypes, involving the main European transformers 

manufacturers. This will start mid 2010 for a two-year 

period. 

INTRODUCTION 

Energy efficiency is a key point in current European 

policies and an environmental necessity for the future. In 

accordance with European laws and decrees, utilities 

involved in the energy sector have to improve equipment, 

networks or grids and demonstrate efforts made in terms 

of energy efficiency and energy savings. Previous studies 

have shown distribution transformers account for the 

majority of losses in electrical European networks with 

total losses of about 33 TWh/y [1] in the EU27 and 4 

TWh/y in the French distribution grid. For the needs of 

ERDF, the french DSO, EDF R&D is carrying out studies 

targeted at efficient distribution transformers. The 

following chart illustrates the losses in the French 

distribution grid. 

Table 1 : Chart of losses accounting on ERDF grid. [2]

Recent decisions of the European Commission order 

utilities of the energy sector to reduce losses on their grid 

and on their equipment. For electrical companies, EDF 

and its subsidiary ERDF, distribution transformers are 

pinpointed as equipment to be improved. Where 

conventional Grain Oriented steel seems to show a 

limitation in the possibility of no-load losses reduction, 

amorphous ribbon technology developed by Hitachi 

Metals/Metglas Inc., allows a significant reduction of 

these losses of wound core transformers. Compared to 

conventional Grain Oriented sheets, amorphous wound 

core based design makes optimum use of the properties of 

amorphous alloys. A reduction up to 60% is expected on 

the no-load losses level [3]. Nevertheless, the transformer 

concept needs to be reviewed to match the amorphous 

ribbon capabilities and shape. The "5-leg transformer" 

concept with 4 or 8 wound cores seems to be an optimum 

design if it complies with electrical behavior requirements 

notably the short circuit test which induces important 

mechanical stresses into the active part. 

Table 2 : Example of 5-leg type wound core transformer

INVESTIGATION ON THE AMORPHOUS 

MATERIAL 

Before a large scale implementation of AMDT on the 

French distribution grid, EDF R&D evaluates the material, 

its magnetic properties, the stability, the chemical 

compatibility, and the safety aspects in case of transformer 

failure. For that, a 3-year Ph. D. program has been 

initiated in 2009, supported by EDF-R&D-LME and titled 

"Study of application of amorphous ribbons in distribution 

transformers for ERDF", in partnership with CNRS-ENS 

Cachan. This first past year was dedicated to the 

characterisation of amorphous ribbons properties (Metglas 

2605 SA1 and HB1) and the study of chemical 

compatibility with mineral oils and natural ester 

potentially used in transformers. The aim of these first 

investigations is to check whether mineral oil and natural 
CIRED Workshop - Lyon, 7>8 June 2010 

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ester have an impact on the amorphous ribbon properties. 

EDF R&D and ENS Cachan have performed an isothermal 

aging test to artificially simulate an environment 

comparable to what the transformer may be exposed to 

over the 30 years of service conditions. The ribbon 

samples were submitted to 140°C heating during 580 

hours, immersed into the three referenced oils usually used 

at ERDF. Magnetic properties were periodically recorded 

and compared to initial values. 

At the end of this test, we concluded the properties are 

stable and no degradations occurred in the samples. This 

step shows the amorphous soft alloys are of interest and 

offer many advantages for efficient transformers 

applications. 

Table 3: Hysteresis cycles measured on G.O steel and 

amorphous ribbon.

The ability of amorphous ribbons to withstand aging was 

checked with XRD measurements. A pure halo is the 

proof of a controlled manufacturing process. 

Table 5: XRD pattern of a SA1 amorphous sample. 

We also pushed the limits of the investigation, studying a 

crystallization under high temperature as the manufacturer 

Hitachi Metals/Metglas describes it at temperature 

thresholds. 

Table 6:XRD patterns of crystallized and amorphous ribbons 

Fe-Si and Fe-B compounds are clearly detectable with 

singular peaks. This situation is out of the normal 

operating range of the amorphous material. 

ERDF REQUIREMENTS

In 2010, ERDF asked transformers manufacturers to 

develop prototypes complying with the current 

transformers specification. Dimensions and weight criteria 

shall be respected and stay similar to those of conventional 

transformers already approved. As for conventional 

transformers, ERDF wishes the next AMDT to withstand 

short-circuit attempts in accordance with IEC 60076-5. 

The sound power level stays similar to that of the last 

generation of transformers already approved. The major 

change is the no-load losses level which will be based on 

EN 50464-1 and will not exceed A0/2. If better 

performance can be reached, it is welcome. 

Short circuit withstand Max deviation 4% (ΔL/L) 

No-load losses level A0 / 2 

ERDF will evaluate the devices having various 

characteristics such as the noise level. The purpose is to 

know the feasibility and the impact of various criteria on 

the final cost of the transformers. 

FIELD TEST EXPERIMENT

For the next couple of years, ERDF plans a trial test with 

some amorphous-core 3-phase transformer prototypes, 250 

and 400 kVA, built early in 2010 by the manufacturers 

who invested in this technology. The purpose of the 

campaign is to build and to install amorphous transformers 

in pad mounted type substations of the ERDF distribution 

grid. They will operate in usual conditions including 

thermal cycles and load cycling. At the end of this 2-year 

period, a sampling of these units will be re-evaluated in 

the laboratory in order to compare their performance with 

their initial data. The noise criteria, the aging, the general 

behaviour, the field team's opinion will be monitored in 

particular. 

CONCLUSIONS 

During the first stage of these investigations, the 

compatibility of amorphous ribbon with mineral oil and 

natural ester was demonstrated. The characterisation step 

brought us a better understanding of the material limits 

and what we can expect from it. Dedicated specification 

for AMDT will be produced soon in 2011, before 

launching an AMDT supply contract in the French 

territory. These long terms investments match the 

commitments of EDF Group in grid losses reduction, 

according to the European requirements on energy 

efficiency and energy savings. 

REFERENCES 

[1] R. Targosz, F. Topalis and W. Irrek, “Selecting 

energy-efficient distribution transformers: A guide for 

achieving least-cost solutions,” SEEDT Project (2008). 

[2] ERDF : Vouloir Savoir n°178, p.1, décembre 2008. 

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1 0 2 0 4 0 6 0 8 0 100 120

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[3] H.W. Ng, R. Hasegawa, A.C. Lee and L.A. 

Lowdermilk, “Amorphous alloy core distribution 

transformers,” Proceedings of the IEEE, (1991), p. 1608-

1623. 

ACKNOWLEDGMENTS 

Frédéric MAZALEYRAT, SATIE, ENS Cachan, CNRS, 

Universud – France. 

ANRT : Association Nationale de la Recherche et de la 

Technologique – Thèse CIFRE Contract N°: 131/2009.