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    Transformer Cooling Classes

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    yasser5
    - The document discusses the cooling classes of transformers and how the designations have changed to be consistent with international standards. - The new classifications have four-letter descriptions indicating the internal cooling medium, circulation mechanism, external cooling medium, and external circulation mechanism. - An example designation of ONAN describes mineral oil cooled internally by natural convection and externally by natural air convection. - A table compares the past and present transformer cooling designations.

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    Transformer Cooling Classes

    Uploaded by

    yasser5
    628 views2 pages
    - The document discusses the cooling classes of transformers and how the designations have changed to be consistent with international standards. - The new classifications have four-letter descriptions indicating the internal cooling medium, circulation mechanism, external cooling medium, and external circulation mechanism. - An example designation of ONAN describes mineral oil cooled internally by natural convection and externally by natural air convection. - A table compares the past and present transformer cooling designations.

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    Cooling classes of power and distribution transformer

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    - The document discusses the cooling classes of transformers and how the designations have changed to be consistent with international standards. - The new classifications have four-letter descriptions indicating the internal cooling medium, circulation mechanism, external cooling medium, and external circulation mechanism. - An example designation of ONAN describes mineral oil cooled internally by natural convection and externally by natural air convection. - A table compares the past and present transformer cooling designations.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    628 views2 pages

    Transformer Cooling Classes

    Uploaded by

    yasser5
    - The document discusses the cooling classes of transformers and how the designations have changed to be consistent with international standards. - The new classifications have four-letter descriptions indicating the internal cooling medium, circulation mechanism, external cooling medium, and external circulation mechanism. - An example designation of ONAN describes mineral oil cooled internally by natural convection and externally by natural air convection. - A table compares the past and present transformer cooling designations.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 2

    Transformer Handbook

    Cooling Classes of Transformers


    NETA World, Spring 2003
    by Ron Widup Shermco Industries

    As a point of clarification, the cooling classes of transformers have changed in recent years and are explained in the following information. The IEEE transformer cooling designations were changed to become consistent with the IEC (IEC 60076-2: 1998). The new classifications are detailed in IEEE C57.12.00-2000. The new cooling designations have four-letter descriptions that indicate specific criteria relative to 1) the type of oil, 2) how the oil is internally circulated, 3) what is used to cool the oil, and 4) how the oil is externally cooled. As an example:
    The type of oil What is used to cool the oil

    Second Letter
    Circulation Mechanism for Internal Cooling Medium Letter Definition N Natural convection flow through cooling equipment and in windings F Forced circulation through cooling equipment (i.e., coolant pumps) and natural convection flow in windings (also called nondirected flow) D Forced circulation through cooling equipment, directed from the cooling equipment into at least the main windings

    Third Letter
    External Cooling Medium Letter A W Definition Air Water

    ONAN
    How the oil is internally circulated How the oil is externally cooled

    Figure 1 Cooling Designations

    Fourth Letter
    The cooling class is identified by the following methodology: Circulation Mechanism for External Cooling Medium Letter N F Definition Natural convection Forced circulation [fans (air cooling) or pumps (water cooling)]

    First Letter
    Internal Cooling Medium in Contact with the Windings Letter O K L Definition Mineral oil or synthetic insulating liquid with fire point 300C Insulating liquid with fire point > 300C Insulating liquid with no measurable fire point

    Comparison of past transformer cooling designations versus present-day transformer cooling designations is detailed in the following table:

     Present Designations ONAN ONAF Previous Designations OA FA

    Transformer Handbook

    ONAN/ONAF/ONAF ONAN/ONAF/OFAF ONAN/ODAF OFAF

    OA/FA/FA OA/FOA FOA FOA

    OA/FA/FOA OA/FOA/FOA FOW FOW

    ONAN/ODAF/ODAF OFWF ODAF ODWF

    Figure 2 Comparison Table, Past/Present Designations

    For more detailed information on transformer cooling class designations, see IEEE Standard C57.12.00-2000, IEEE Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers.

    Ron A. Widup, Executive Vice President/General Manager of Shermco Industries, Inc., has over 20 years of experience in the low-, medium-, and high-voltage switchgear and substation market. He is a principal member of NFPA technical committee 70E (Electrical Safety Requirements for Employee Workplaces) and a member of NEC Code Panel 11. He is past president of NETA and currently a member of the Board of Directors and Standards Review Council. He is certified as a NETA Level IV Senior Test Technician.

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