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طلب مساعدة للحاجه الماسه عن طرق تبريد محولات القدرة الكهربائية

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  1. [1]
    تيام الشريف
    تيام الشريف غير متواجد حالياً

    جديد

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    طلب مساعدة للحاجه الماسه عن طرق تبريد محولات القدرة الكهربائية

    بسم الله الرحمن الرحيم
    السلام عليكم ورحمة الله تعالى وبركاته
    انا طالب السنة الثالثه في كلية الهندسة الكهربائي
    اطلب من الاخوة في المنتدى المساعدة وذلك بافادتي بمعلومات بالتوصيف
    عن طرق تبريد محولات القدرة وذلك إن امكن خلال يومان
    ولكم جزيل الشكر
    tiyam

  2. [2]
    elsayed_na
    elsayed_na غير متواجد حالياً
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    عزيزى المهندس/ تيام الشريف
    طرق تبريد محولات القوى
    1- عن طريق الزيت الطبيعى و الهواء الطبيعى oil natural air natural
    onan
    2- عن طريق الزيت الطبيعى و الهواء القسرى oil natural air forced
    onaf
    3- عن طريق الزيت القسرى و الهواء الطبيعى oil forced air natural
    ofan
    4- عن طريق الزيت القسرى و الهواء القسرى oil forced air forced
    ofaf
    التبريد الطبيعى يكون عن طريق سطح المحول الخارجى للهواء الجوى
    التبريد القسرى يتم بالتحكم فى الوسط المحيط بالمحول والسائل المستخدم فى التبريد
    وتجد هذة الختصارات مكتوبة على لوحة البيانات الخاصة بالمحول

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  3. [3]
    م عاطف عبدالرحمن
    م عاطف عبدالرحمن غير متواجد حالياً
    عضو فعال
    الصورة الرمزية م عاطف عبدالرحمن


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    التحكم فى الهواء والزيت عن طريق المراوح و pump

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  4. [4]
    تيام الشريف
    تيام الشريف غير متواجد حالياً
    جديد


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    طرق تبريد محولات القوى
    1- عن طريق الزيت الطبيعى و الهواء الطبيعى oil natural air natural
    onan
    2- عن طريق الزيت الطبيعى و الهواء القسرى oil natural air forced
    onaf
    3- عن طريق الزيت القسرى و الهواء الطبيعى oil forced air natural
    ofan
    4- عن طريق الزيت القسرى و الهواء القسرى oil forced air forced
    ofaf
    التبريد الطبيعى يكون عن طريق سطح المحول الخارجى للهواء الجوى
    التبريد القسرى يتم بالتحكم فى الوسط المحيط بالمحول والسائل المستخدم فى التبريد
    وتجد هذة الختصارات مكتوبة على لوحة البيانات الخاصة بالمحول



    بسم الله الرحمن الرحيم
    السلام عليكم ورحمة الله تعالى وبركاته
    الاخ المهندس / السيد
    لك الشكر الجزيل على ايفائي بهذه المعلومات القيمه والجيده
    ولكني اطلب من سيادتكم وكلي أمل أن توفيني بتفصيل عن المعلومات التي في أعلي المشاركة وذلك لاتمام بحث قد طلب مني وتسليمه خلال يومان من تارخ ارسال المشاركة
    وجزاك الله خيراً
    المهندس / تيام الشريف

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  5. [5]
    tamerrezek
    tamerrezek غير متواجد حالياً
    جديد


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    اليك بعض التفاصيل:
    6.3 COOLING EQUIPMENT
    Heat from core losses and copper losses must be dissipated to the environment.
    In dry type transformers, cooling is accomplished simply by circulating air
    around and through the coil and core assembly, either by natural convection
    or by forced air flow from fans. This cooling method is usually limited to
    low-voltage indoor transformers (5 kV and below) having a three-phase rating
    below 1500 KVA. At higher voltages, oil is required to insulate the windings,
    which prevents the use of air for cooling the core and coils directly. At higher
    KVA ratings, the losses are just too high for direct air cooling to be effective.
    In outdoor environments, direct air cooling would introduce unacceptable
    amounts of dirt and moisture into the windings.


    Transformers come in various
    cooling classes, as defined by the industry
    standards. In recent years, there have been attempts to align the designations
    that apply to transformers manufactured in North America with the IEC
    cooling-class designations.

    Table 6.1 [1] gives the IEC designations and the
    earlier designations that are used in this book. All of the IEC designations use
    four letters. In some respects, the IEC designations are more descriptive than
    the North American designations because IEC makes a distinction between
    forced-oil/air cooled (OFAF) and directed-flow-air cooled (ODAF). Some
    Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
    T


    ABLE 6.1 Designations and Descriptions of the Cooling Classes Used
    in Power Transformers
    Previous
    designation IEC designation Description
    OA ONAN Oil-air cooled (self-cooled)
    FA ONAF Forced-air cooled
    OA/FA/FA ONAN/ONAF/ONAF Oil-air cooled (self-cooled), followed by
    two stages of forced-air cooling
    (fans)
    OA/FA/FOA ONAN/ONAF/OFAF Oil-air cooled (self-cooled), followed by
    one stage of forced-air cooling (fans),
    followed by 1 stage of forced oil (oil
    pumps)
    OA/FOA ONAN/ODAF Oil-air cooled (self-cooled), followed by
    one stage of directed oil flow pumps
    (with fans)
    OA/FOA/FOA ONAN/ODAF/ODAF Oil-air cooled (self-cooled), followed by
    two stages of directed oil flow pumps
    (with fans)
    FOA OFAF Forced oil/air cooled (with fans) rating
    only—no self-cooled rating
    FOW OFWF Forced oil/water cooled rating only (oil/
    water heat exchanger with oil and water
    pumps)—no self-cooled rating
    FOA ODAF Forced oil/air cooled rating only with directed
    oil flow pumps and fans—no
    self-cooled rating
    FOW ODWF Forced oil/water cooled rating only (oil/
    water heat exchanger with directed
    oil flow pumps and water pumps)—
    no self-cooled rating
    Source


    : Ref. 1.
    people find using the four-letter designations somewhat awkward, and this
    book uses the earlier designations throughout.
    In small oil-filled distribution transformers, the surface of the tank is
    sufficient for transferring heat from the oil to the air. Ribs are added to the
    tanks of some distribution transformers to increase the surface area of the tank
    and to improve heat transfer. Large distribution transformers and small power
    transformers generally require radiator banks to provide cooling. Regardless
    of whether the tank surface, ribs, or radiators are used, transformers that trans-
    Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
    fer heat from oil to air through natural convection are all cooling class OA
    transformers.
    Radiators used on OA transformers generally have round cooling tubes
    or flat fins with large cross section areas in order to allow oil to flow by natural
    convection with minimal resistance. Hot oil from the core and coils rises to
    the top of the tank above the inlet to the radiator. Cool oil from the radiator
    sinks to the bottom of the radiator through the outlet and into the bottom of
    the core and coils. This process is called thermo-siphoning and the oil velocity
    is relatively slow throughout the transformer and radiators. For this reason,
    OA transformers have relatively large temperature gradients between the bottom
    oil and the top oil, and relatively large temperature gradients between the
    winding temperatures and the top oil temperature. Likewise, the air circulates
    through the radiator through natural convection, or is aided by the wind.
    As the transformer losses increase, the number and size of the radiators
    that are required to cool the oil must increase. Eventually, a point is reached
    where wind and natural convection are not adequate to remove the heat and
    air must be forced through the radiators by motor-driven fans. Transformers
    that have forced air cooling are cooling class FA transformers. FA transformers
    require auxiliary power to run the fan motors, however, and one of the
    advantages of OA transformers is that they require no auxiliary power for
    cooling equipment. Since additional cooling is not usually needed until the
    transformer is heavily loaded, the fans on most FA transformers are turned
    off until temperatures exceed some threshold value, so under light load the
    transformer is cooled by natural convection only. These transformers are cooling
    class OA/FA transformers.
    Some transformers are cooled by natural convection below temperature
    T


    1, turn on one stage of fans at a higher temperature T2 and turn on a second
    stage of fans at an even higher temperature

    T3. These transformers are cooling
    class OA/FA/FA transformers. The direction of air flow in forced-air units is
    either horizontally outward or vertically upward. The vertical flow pattern has
    the advantage of being in the same direction as the natural air convection, so
    the two air flows will reinforce each other.
    Although the cooling capacity is greatly increased by the use of forced
    air, increasing the loading to take advantage of the increased capacity will
    increase the temperature gradients within the transformer. A point is reached
    where the internal temperature gradients limit the ability to increase load any
    further. The solution is to increase the oil velocity by pumping oil as well as
    forcing air through the radiators. The usual pump placement is at the bottom
    of the radiators, forcing oil from the radiator outlets into the bottom of he
    transformer tank in the same direction as natural circulation but at a much
    higher velocity. Such transformers are cooling class FOA transformers. By
    Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
    directing the flow of oil within the transformer windings, greater cooling efficiency
    can be achieved. In recognition of this fact, the calculation of hot-spot
    temperatures is modified slightly for directed-flow cooling class transformers.
    As in forced-air designs, forced-oil cooling can be combined with OA
    cooling (OA/FOA) or in two stages (OA/FOA/FOA). A transformer having
    a stage of fans and a stage of oil pumps that are switched on at different
    temperatures would be a cooling class OA/FA/FOA transformer.
    The radiator design on FOA transformers can differ substantially with
    the radiator design on FA transformers. Since the oil is pumped under considerable
    pressure, the resistance to oil flow is of secondary importance so the
    radiator tubes can be designed to maximize surface area at the expense of
    cross section area. FOA radiators are sometimes called coolers instead, and
    tend to resemble automotive radiators with very narrow spaces between the
    cooling tubes and flat fins in the spaces between the cooling tubes to provide
    additional surface area. The comparison of the two types is illustrated in Figures
    6.7 (OA/FA type) and 6.8 (FOA type).
    F


    IGURE 6.7 OA/FA radiator construction. The large radiator tubes minimize restriction
    of oil flow under natural convection. The fan is shown mounted at the bottom
    with air flow directed upward.
    Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
    F


    IGURE 6.8 FOA cooler construction. The oil is forced through narrow tubes
    from top to bottom by means of oil pumps. The cooling fans direct air horizontally
    outward.
    Cooling equipment requires maintenance in order to run efficiently
    and provide for a long transformer life. There is the obvious need to maintain
    the fans, pumps, and electrical supply equipment. The oil coolers themselves
    must be kept clean as well, especially FOA-type coolers. Many
    transformers have overheated under moderate loads because the cooling fins
    were clogged with insect and bird nests, dust, pollen, and other debris. For
    generator step-up transformers, where the load is nearly at nameplate rating
    continuously, steam-cleaning the coolers once every year is a good maintenance
    practice.

    Copyright © 2002 by Marcel Dekker, Inc. All Rights Reserved.
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  6. [6]
    حماده راجح
    حماده راجح غير متواجد حالياً
    عضو


    تاريخ التسجيل: Sep 2009
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    طرق تبريد المحول
    methods of cooling transformer

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