Quality Program

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Quality Assurance

The quality assurance in Elprom Heavy Industries is performed according to a Quality Management System certified under ISO 9001:2015.

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The quality control includes:


Incoming quality control of all materials and accessories. 


  • All materials undergo different types of incoming quality control. Materials essential for the overall quality of our products undergo tests in the company testing laboratories.


Quality control during manufacturing.


  • During the manufacturing process all stages are monitored according to approved by the top management Quality plan.

End control and testing.


  • All transformers undergo routine tests according to IEC 60076, IEEE or other international standard as specified by the client.
  • On client’s demand by the client additional special and type tests are performed.
  • All tests are performed on-site in Elprom Heavy Industries testing laboratories, except short circuit withstand.
  • The transformer short circuit withstand capability is proved by means of calculations.
  • On client's demand the tests can be performed in internationally acknowledged independent laboratories such as KEMA - Holland, CESI - Italy, ICMET - Romania.

Laboratory "Transformers"


Transformers Laboratory has an Accreditation Certificate № A243 / 14.01.2022 according to ISO 17025 with the scope specified in Order № A39 / 14.01.2022 (you can find them on our page).
The laboratory conducts type, rutine and special tests in accordance with the international standards and customer requirements.

For the needs of Transformers laboratory, there is a generator room and it can provides voltages with a frequency of 50, 60 and 200 Hz.

The following tests of Transformers can be performed in the laboratory:
• Turn-ratio measurement and phase displacement:
• DC resistance of the windings
• No-load losses and harmonics in no-load current
• Short-circuit impedance and load losses
• Zero-sequence impedance
• Heat-run test and power consumption of cooling system
• Sound-level and vibrations measurement
• Watt balance test
• C and power factor measurements of the insulation
• Insulation resistance
• Oil breakdown voltage measurement
• Lightning Impulse voltage test including chopped wave
• Switching Impulse voltage test
• Separate source AC withstand voltage test
• Induced overvoltage test
• Partial discharges measurement
• Transients transferred through the windings

The scope of accreditation of the laboratory also includes the following tests of Tap Changers for transformers:
• Full wave lightning impulse test (LI)
• Chopped wave lightning impulse test (LIC)
• Switching impulse test (SI)
• Applied voltage test (AV)
• Measurement of partial discharges



2022.07.29-ILT_EHI_Certificate ISO 17025-2018-BG_page-0001.jpg
BAS reg. number: 243 ЛИ
2022.07.29-ILT.EHI_Order No. A 485_BG
ILT tests