Аbout us

We are “ELPROM TRAFO CH” PLC – for 5 decades we have been offering our main product and trademark – the oil immersed distribution transformer.


We are on the market since 1968. Our plant is established on the 28th of March the same year in the town of Kyustendil as a subdivision of the existing “Plant for power transformers” in Sofia. During the seventies of the past century, starts the production of the FIRST TYPE OF TRANSFORMER TM 100 kVA and its regular production follows. One decade later the plant achieves significant development, it is renewed technologically, expands and the production range is extended. The maximum production capacity of the plant has been reached before the end of the past century – 10 000 pieces of transformers are being manufactured annually. Nowadays we have control laboratories for incoming, current and outgoing control of the materials, used in the production, as well as testing laboratory for routine and type testing of the transformers.
THE TRUE LOOK OF THE ENTERPRISE has been formed during the nineties of the XX century. We have special design and technological departments, thereby the production cycle becomes fully closed – from the design of the transformer to its assembly, in accordance with the requirements of the end customer and every related national and international standard.

This is our path through the years – a path of tradition and continuous renewal. You, our customers know well that without solid foundation and clear goals there is no development, and we have both.


At this moment “Elprom Trafo” is a manufacturer with its own proven “know-how” with continuous presence on the Bulgarian and International markets. For more than 10 years now the plant has an established and certified quality management system acc. to БДС EN ISO 9001 and this makes it competitive and adaptive in the current market conditions. The company has QUALITY CERTIFICATES according to the systems БДС EN ISO 9001:2015, БДС EN ISO 14001:2015 и БДС EN ISO 45001:2018. The quality procedures, according to БДС EN ISO 9001:2015, cover the entire production – from the incoming control of the materials, through the design and manufacture, to the output tests and the shipment of the ready product. The plant introduces a good working system, organized and maintained by high quality experts. We have a developed and introduced automated system for management of the purchase orders, management system for the technical documentations and management system of the material base of the plant. We also have another advantage – the especially for us designed software for optimal design of transformers. We can now shorten the production period to a maximum and this way – spare your time.

Our production is maximally extended – we manufacture the full range of oil immersed distribution transformers with rated power from 25 kVA up to 5 000 kVA. “Elprom Trafo” also manufactures special type of transformers, such as: ground transformers, transformers for wind generators, transformers for photo-voltaic stations, transformers with voltage step regulators and mono phase transformers. For each rated power we offer different series, depending on the no-load and load losses.

EVERY TRANSFORMER IS MANUFACTURED IN COMPLIANCE WITH THE INTERNATIONAL STANDARD БДС EN 50588-1:2018 (successor of HD 428.1S1 and БДС EN 50464-1:2007). The oil transformers, which are manufactured as standard series of losses, work at frequency f=50Hz (60Hz), air temperature up to 50 °C and altitude up to 2500 m. Upon customer`s request it is possible modifications to be made, depending on the working conditions, number of phases, vector group, etc.

Currently, since July 2015, because of the enactment of Regulations 548/2014 and 1783/2019 of the European Commission for Eco-design transformers, in force for the whole territory of the European Union, the entire production is brought in full compliance with the new requirements.