Manufacture of Transformers in Bulgaria and Serbia

Electronics IndustrySouth-East European INDUSTRIAL Мarket - issue 1/2011

Power, distribution and measurement transformers are actively produced in Bulgaria and Serbia. The manufacturing technologies are compatible with the world standards and the device quality is high. Most of the producers meet any specific individual power requirements and aim to supply cost effective and reliable power solutions that work for the customers and the environment. The equipment comes with leading industry guarantees. The article lists major Bulgarian and Serbian manufacturers, information about each company and a short review of their product portfolio.

Key Bulgarian manufacturers

ANG company is one of the leading manufacturers of transformers, adapters and switching power supplies at the Bulgarian market since 1992. The company produces transformers for PCB mounting, current transformers, toroidal power transformers, switching transformers based on all kinds of ferrites, etc. Manufactured transformers are 1.3VA, 1.5VA, 2VA, 6VA, 18VA and 24VA with a wide range of output voltages. ANG has a closed production cycle, in which high quality materials from leading European and world-known suppliers are used. The company has machines for winding of voltage, current and toroidal transformers as well as closed-cycle production of adapters with its own unique design and high quality. ANG company holds a major share of the market for power supplies in Bulgaria and the high quality and 100% control over the production allows covering of the European and world markets.

AQ Magnit is specialized in manufacture of transformers, inductors, cabling and electrotechnical assembly. Its production facilities in town of Godech occupy 7 000 m2 area. Main manufacturing methods in the enterprise are profile and wire winding of inductive components and vacuum/pressure impregnation (VPI). The company is a part of Aros Quality Group. The group has two business segments: Components, which produces transformers, cables, plastic injection moulding, and metal stamping, and Systems which develops and produces power- and automation solutions in close collaboration with the customer. The Group has approximately 2,000 employees worldwide in Sweden, Bulgaria, China, Estonia and Italy.

Bistra Todorova 99 is a long-term producer of network power transformers, chokes and coils. All of its products are available in small-, medium- and large-size series as well as single units. Major product lines include: Transformers fulfilled with EI Lamella from 8 VA to 40 VA (optional: thermal fuse); Transformers fulfilled with EI Lamella from 40 VA to 250 VA with open isolated leads, pins and with terminal block (optional: fuse); Transformers fulfilled with EI Lamella from 250 VA to 6000 VA with open isolated leads, with terminal block (optional: fuse) and with copper terminals.
In its manufacturing process Bistra Todorova 99 Ltd. uses modern winding machines with wide range of application for winding. Transformers are impregnated to cover required isolating characteristic IP 00. The company developed and put into practice system for quality management, which satisfied regulations of the standard EN ISO 9001:2000.

Bultraf Ltd was founded in 2004. The company specializes in the manufacture and supply of chokes and small to middle-sized transformers. The transformers production conforms to the international tendencies and meets the requirements of European standards as well as the customers’ technical specification: number of turns, creapage distances, isolation and method of winding. Its annual capacities are equal to: pulse transformers over 2,000,000 pcs; transformers for printed boards over 200,000 pcs; transformers for electric panels over 100,000 pcs; single-phase transformers over 10,000 pcs and three-phase transformers over 5,000 pcs.
The company has at disposal up-to-date machinery and equipment for the achievement of optimal technology of the production activities. Its production process includes low-powered and middle-powered transformers and chokes winding process - production of optimal powers for all articles, sequence and winding direction control; low-powered transformers winding process – O0.03mm wire are used on multi-spindled automatic machines, achievement of fast speed up to 6000 rev./min; Low-powered transformer potting process include two-component epoxy resin potting for products up to 50VA and precise potting machine to achieve outstanding accuracy and speed for doses from 2gr to 200gr. For transformer impregnation process is constructed a technological automatic line to impregnate and bake production with fine temperature control in all oven areas. Bultraf company performs 100% tests over the whole production with top-class precision features lab equipment from leading companies in the field of testing installations and appliance.

Centralna Energoremontna Baza (CERB) was established in 1948 and today is recognized as a reliable supplier of repair services to the power facilities within the electric power sector in Bulgaria and manufacturer of power and distribution transformers. The Company disposes of 20 000 sq. m. built-up area including production buildings, store facilities, oil storage reservoirs with capacity up to 380 t, laboratories and test stations, administrative buildings. Its scope of activity includes manufacture of power transformers - rated output up to 80MVA and rated voltages up to 110 kV and distribution transformers - rated output up to 1600 kVA and rated voltages up to 35 kV. Also the company is producing dry transformers with rated output up to 1000 kVA and rated voltages up to 20 kV.

Elprom-EMZ is specialized in manufacturing and realization of power measuring transformers low voltage and average voltage with category of precision 0.2 S and 0.5 S and nominal capacity from 5 to 15 VA in range of nominal electricity from 5/5/5 A to 5000/5/5 A. Also the company is manufacturing one-phase oil transformers for pillar mounting with nominal power from 1 kVA up to 50 kVA. Its activities include overhaul of power oil three-phase transformers TM type from 25 kVA up to 1000 kVA on 6 kV, 10 kV or 20 kV.

Elprom Trafo was established in 1968 in   Kyustendil as a subsidiary of the existing Power Transformer Factory in Sofia. Except the full range of three-phase oil-filled distribution transformers with rated power from 25kVA up to 2500kVA Elprom Trafo CH manufactures special types of transformers, such as: earthing transformer, transformer for wind turbines, with on load tap-changers and single phase transformers. Different series are offered for each power, depending on no-load losses and load losses. Each transformer is manufactured in accordance with the international standard series of oil-filled transformers operate at frequency of 50Hz (60Hz), ambient temperature up to 50oC and altitude up to 1000m. Special modifications according to work conditions, number of phases, vector-croup symbol as well as single phase transformers can be made upon customer request. The manufacturing process is automated to the highest degree and divided in two workshops at a total area of 25 000m2. The plant holds possession of a unique, for the territory of Bulgaria, laboratory complex, equipped with one of a kind installations and qualified specialists. In its facilities incoming, routine and outgoing control of materials and ready-made production is being done. At the moment 70% of the total production of Elprom Trafo CH is shipped abroad and 30% goes to the home market. Its long term business partners are countries from North Africa, Asia, South America, Balkan region and Near East.

Eltraf-DM is specialized in production of single-phase transformers from 10VA up to 50 kVA; three-phase transformers up to 50 kVA; phase chokes and coils. Transformers are manufactured according to design of the products in which they are consumed. Used insulating materials and conductors are with thermal class F and H. Impregnating compounds for vacuum impregnation based on epoxy resins and lacquers provide work temperature range of items from – 40oC to +50oC.

Eltraf - Rumen Radev is a manufacturer of single-, doble- and three phase tran-sformers for low, medium and high (up to 5KV) voltage. Furthermo-re, the company offers transformers for flash and spot welding.

Company is focused on production of plate transformers, electronic transformers, electronic transformers for lighting, toroidal transformers and current transformers.

In 1997 Hyundai Heavy Industries Ltd., Electro Electric Systems took over the Bulgarian state owned Elprom-Trafo company which has been well-known manufacturer of power transformers and tap changers. The heritage of the Bulgarian company is - well educated human resources, developed technology and know how regarding particular branches of industry were the basement for successful beginning of Hyundai Heavy Industries Korea in order to generate more competitive power of the Bulgarian manufacturer. In 2001 the company name has been changed to “Hyundai Heavy Industries Co. Bulgaria” JSC. Reliable operation of company products is proved in many countries of Europe, Asia, Africa, Middle East, Latin America.
Hyundai Heavy Industries Co. Bulgaria manufactures oil-immersed power transformers to meet the needs of the electric power system of Bulgaria as well as the demands of foreign customers - for power substations, thermal power plants, hydro-electric power plants, industrial enterprises etc. 
Product range includes single phase power transformers with copper windings and ratings up to 250 MVA and voltages up to 400 kV; autotransformers of rating up to 250 MVA at voltages up to 400 kV; generator transformers of ratings up to 275 MVA, power transformers with OLTC/OCTC 3 phase up to 250 MVA.


ISOMATIC Lab designs and manufactures transgun transformers for manual and robot resistance welding in the automotive and other sheet metal and wire processing industries. There are 2 transformer lines -for 50/60 Hz up to 125 kVA and transformer/rectifiers for 1000/1200 Hz up to 300 kW. Several models of SCR controlled weld power sources, precision weld controllers, weld current meters up to 100 kA, Rogowski sensors and others are available too. Small welding heads for microwelding are manufactured for the electrotechnical and instrumentation industries worldwide. Another area of activity are special welding machines designed to customer specification.

The company was established in 1996 as a private association with a subject of activity production, sale, and repair of dry and oil transformers for medium and low voltage construction of transformer substations type MKTP. Lemi Trafo also trades with electro materials, building and repair of electro equipment up to 110kV. The company has its own facilities located in industrial zone of Pernik, which includes an open storage area of 12,000 m2, a covered storage area of 2500 m2 and workshop for the manufacture of transformers with an area of 8150 m2. The base is equipped with modern machinery.

Company Telkor ltd. was established in 1996 with main activity production and export of transformers, adapters and drossels. The trade strategy of TELKOR Ltd. is oriented towards medium scale and small scale manufacturers of electronic devices. The production of the company is designed mostly for electronic and electrotechnical appliances: computing technique, measuring and controlling devices, cash registers and security systems. The transformers are widely used as supplying and separating transformers in machine building and in hoisting devises. The quality and efficiency of the production is provided by machines and equipment of last generation and by highly qualified personnel.

Novatech Ltd. manufactures toroidal transformers from 10VA to 2500VA. The production site is equipped with German and Japanese machines, which enable mass production with perfect quality. Toroidal transformers are used in telecom products, industrial systems, audio systems, medical equipment, data transmission, computers, lighting, etc.

Company is specialized in the production of dry low power transformers and processing metal parts on cutting, milling and turning CNC-machines. The full scope of the various types of transformers produced in UNITRAF JSC includes: transformers for printed boards 1,5-24 VA; toroidal transformers 20-1200 VA; transformers with lamination cores 1,5-800 VA; transformers with wound cores 5-2000 VA (Type A); common type transformers 10-100 VA (Type B); monophase transformers and chokes 2-12 kVA; three-phase transformers and chokes 0,3-40 kVA; monophase and three-phase transformers and chokes for welded machines; autotransformers. Production capacity of Unitraf Sokolovo is hundreds of thousands transformers annually. They are widely used in electronic and electrical industry, radio and television equipment, household appliances, computing, measuring and control equipment, audio and video equipment, welding machines, etc. Also they are widely used as operational and separating transformers in mechanical and materials handling equipment and medical equipment.

UNITRAFAD Ltd has longtime experience in producing different transformers by type and purpose. Its production is used widely in electrical, mechanical and electronic engineering. The company produces transformers from 2 VA up to 100 KVA - mono-phase transformers of mantle-type, kernel-type and toroidal-type core; three-phase transformers; mono-phase and three-phase chokes; welding and plasma-cutting transformers; high-voltage transformers for HF generators; coil products; power supply products; magnetic circuits. Apart from the traditionally produced transformers different special-type transformers are produced on clients’ request. The production area of the company is located in village of Dryanovo.

VIKI - B Ltd. was founded in 1995. Its main activity is related to production of transformers - all types of single phase transformers from 12 W to 10,000 W and three-phase power transformers from 100 W to 80000 W. In addition company is manufacturing LED street lighting, chargers for traction batteries (transformer and inverter); welding machines and equipment.

ZAVN Dobrich
The company is specialized in manufacture of current measuring transformers for indoor installation 0,5 kV and current measuring voltage transformers 10, 20 and 35 kV, designed for measurement of alternating current from 10 to 4000 A for installation in indoor switchboards and devices. Voltage instrument transformers for the nominal operating voltage of 6, 6.3, 10, 15 and 20 kV are to be installed in indoor facilities. The company has its own manufacturing facilities and warehouse with total of 5,000 m2.

Key Serbian manufacturers

ABS Minel Trafo was established in the city of Mladenovac, Serbia, in 1958. The company has been a subsidiary of ABS Electro since 2005. Today it employs over 300 people. Over the past few decades the company has gained experience in design, manufacture, testing and maintenance of oil-filled and dry-type distribution transformers, autotransformers, regulating transformers, earthing transformers and special-purpose transformers, as well as oil and air chokes. Over 70% of the company’s production is sold in the EU countries, the Russian Federation, Africa, South America and Asia. ABS Minel Trafo has an established quality management system in conformity with the requirements for ISO 9001, ISO 14001 standards, and has a large number of certificates for its transformers, as tested by accredited laboratories in conformity with the IEC, GOST and other international and national standards.

The company is engaged in manufacturing and servicing of network, intermediate and three-phase transformers; print transformers sealed and dry; pulse transformers - different voltage levels and power ; classic transformers with elements for attachment, transformers in a safe variant for medical equipment, gas stations, etc.; portable transformers up to 20kV; isolating transformers; auto transformers, etc.

Measuring Transformers Factory (FMT) was founded in 1969. Since its establishment the company is being present on market for electrical equipment with production of low voltage current measuring transformers and insulators for voltages up to 35 kV. Conditions for production of current and voltage transformers were fulfilled by buying a plant for vacuum casting in 1972. At the end of 2005 Measuring Transformers Factory was privatized and since then it undertook the substantial investments with the goal to modernize the production. MTF invests in modernization of production by acquiring new machines and equipment and by implementing new technologies. Its products have found their way to the customers in more than 15 countries from all around the world. The company has business cooperation with the companies from Slovenia, Bosnia and Herzegovinia, FYR Macedonia, Montenegro, Greece, Czech Republic, Estonia, Australia, Romania, Tanzania, United Arabian Emirates, Yemen, Algerie, Nigeria and Thailand.

The company “Stevanovic trafo” was established in February 2002 with the idea to offer wound components and transformers for different purposes. Its initial production program includes transformers for mounting on printed circuit board PCB, power transformers for vertical mounting with P armor and different types of network and audio transformers with “L” brackets for mounting. Today most of the production program is a classic power transformers, single phase and three phase, then the audio transformers, safety transformers for medical facilities, encapsulated transformers and transformers for special applications.

Trafco was founded in 1990 in Belgrade. It is dealing with the production and repair of toroidal transformers in power range from 20 - 3000VA, and auto-transformers up to 5000VA. The core of the transformers is built of quality trafo metal sheets, vacuumed in deep vacuum in order to avoid the transformer humming. Transformers are covered with the domestic and imported lacquer wires. Verification of compliance with JUS standards was performed by the Institute of electro-engineering “Nikola Tesla” in Belgrade.