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speed control for induction motor

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  1. [1]
    حليمه..........
    حليمه.......... غير متواجد حالياً

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    speed control for induction motor

    السلام عليكم ورحمه االله وبركاته

    تحياتي الى ادارة واعضاء هذا المنتدى الناجح

    كما ارغب منكم المساعده في كيفيه تصميم برنامج للتحكم بسرعه Three phase induction motor

    1250RPM

    حيث اني بحثت كثيرا في هذا الموضوع ولم اجد الا طريقه واحده وهي ال frequency converter

    لاكن ليس لدي الكثير من المعرفه في هذه الطريقه لذى ارجو منكم المساعده في هذا الموضوع واكون لكم من الشاكرين.

    من مواضيع حليمه.......... :


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  2. [2]
    المتوكلة على الله
    المتوكلة على الله غير متواجد حالياً
    عضو متميز


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    Three-phase AC induction motors

    Three phase AC induction motors rated 1 Hp (746 W) and 25 W with small motors from CD player, toy and CD/DVD drive reader head traverse



    Disassembled 250W motor from a washing machine. The 12 stator windings are in the housing on the left. Next to it is the "squirrel cage" rotor on its shaft.


    Where a polyphase electrical supply is available, the three-phase (or polyphase) AC induction motor is commonly used, especially for higher-powered motors. The phase differences between the three phases of the polyphase electrical supply create a rotating electromagnetic field in the motor.
    Through electromagnetic induction, the rotating magnetic field induces a current in the conductors in the rotor, which in turn sets up a counterbalancing magnetic field that causes the rotor to turn in the direction the field is rotating. The rotor must always rotate slower than the rotating magnetic field produced by the polyphase electrical supply; otherwise, no counterbalancing field will be produced in the rotor.
    Induction motors are the workhorses of industry and motors up to about 500 kW (670 horsepower) in output are produced in highly standardized frame sizes, making them nearly completely interchangeable between manufacturers (although European and North American standard dimensions are different). Very large induction motors are capable of tens of thousands of kW in output, for pipeline compressors, wind-tunnel drives and overland conveyor systems.
    There are two types of rotors used in induction motors.
    Squirrel Cage rotors: Most common AC motors use the squirrel cage rotor, which will be found in virtually all domestic and light industrial alternating current motors. The squirrel cage takes its name from its shape - a ring at either end of the rotor, with bars connecting the rings running the length of the rotor. It is typically cast aluminum or copper poured between the iron laminates of the rotor, and usually only the end rings will be visible. The vast majority of the rotor currents will flow through the bars rather than the higher-resistance and usually varnished laminates. Very low voltages at very high currents are typical in the bars and end rings; high efficiency motors will often use cast copper in order to reduce the resistance in the rotor.
    In operation, the squirrel cage motor may be viewed as a transformer with a rotating secondary - when the rotor is not rotating in sync with the magnetic field, large rotor currents are induced; the large rotor currents magnetize the rotor and interact with the stator's magnetic fields to bring the rotor into synchronization with the stator's field. An unloaded squirrel cage motor at synchronous speed will consume electrical power only to maintain rotor speed against friction and resistance losses; as the mechanical load increases, so will the electrical load - the electrical load is inherently related to the mechanical load. This is similar to a transformer, where the primary's electrical load is related to the secondary's electrical load.
    This is why, as an example, a squirrel cage blower motor may cause the lights in a home to dim as it starts, but doesn't dim the lights when its fanbelt (and therefore mechanical load) is removed. Furthermore, a stalled squirrel cage motor (overloaded or with a jammed shaft) will consume current limited only by circuit resistance as it attempts to start. Unless something else limits the current (or cuts it off completely) overheating and destruction of the winding insulation is the likely outcome.
    Virtually every washing machine, dishwasher, standalone fan, record player, etc. uses some variant of a squirrel cage motor.
    Wound Rotor: An alternate design, called the wound rotor, is used when variable speed is required. In this case, the rotor has the same number of poles as the stator and the windings are made of wire, connected to slip rings on the shaft. Carbon brushes connect the slip rings to an external controller such as a variable resistor that allows changing the motor's slip rate. In certain high-power variable speed wound-rotor drives, the slip-frequency energy is captured, rectified and returned to the power supply through an inverter.
    Compared to squirrel cage rotors, wound rotor motors are expensive and require maintenance of the slip rings and brushes, but they were the standard form for variable speed control before the advent of compact power electronic devices. Transistorized inverters with variable-frequency drive can now be used for speed control, and wound rotor motors are becoming less common. (Transistorized inverter drives also allow the more-efficient three-phase motors to be used when only single-phase mains current is available, but this is never used in household appliances, because it can cause electrical interference and because of high power requirements.)
    Several methods of starting a polyphase motor are used. Where the large inrush current and high starting torque can be permitted, the motor can be started across the line, by applying full line voltage to the terminals (Direct-on-line, DOL). Where it is necessary to limit the starting inrush current (where the motor is large compared with the short-circuit capacity of the supply), reduced voltage starting using either series inductors, an autotransformer, thyristors, or other devices are used. A technique sometimes used is star-delta starting, where the motor coils are initially connected in wye for acceleration of the load, then switched to delta when the load is up to speed. This technique is more common in Europe than in North America. Transistorized drives can directly vary the applied voltage as required by the starting characteristics of the motor and load.
    This type of motor is becoming more common in traction applications such as locomotives, where it is known as the asynchronous traction motor.
    The speed of the AC motor is determined primarily by the frequency of the AC supply and the number of poles in the stator winding, according to the relation:
    Ns = 120F / p where
    Ns = Synchronous speed, in revolutions per minute F = AC power frequency p = Number of poles per phase winding Actual RPM for an induction motor will be less than this calculated synchronous speed by an amount known as slip, that increases with the torque produced. With no load, the speed will be very close to synchronous. When loaded, standard motors have between 2-3% slip, special motors may have up to 7% slip, and a class of motors known as torque motors are rated to operate at 100% slip (0 RPM/full stall).
    The slip of the AC motor is calculated by:
    S = (NsNr) / Ns percentageslip = (NsNr) / Ns * 100 where
    Nr = Rotational speed, in revolutions per minute. S = Normalised Slip, 0 to 1. As an example, a typical four-pole motor running on 60 Hz might have a nameplate rating of 1725 RPM at full load, while its calculated speed is 1800 RPM.
    The speed in this type of motor has traditionally been altered by having additional sets of coils or poles in the motor that can be switched on and off to change the speed of magnetic field rotation. However, developments in power electronics mean that the frequency of the power supply can also now be varied to provide a smoother control of the motor speed.

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    على الله توكلوا .........ولا تتواكلوا
    يا سادتي..
    لا ترفعوا تلك الأيادي للسماء..
    لا ترفعوها إنها لن تستجيب..
    هل يستجيب الله صوت العاجزين؟!
    من قد أضاعوا الدين واحترفوا البكاء!!
    من حرروا الأرض السليبة بالقعود وبالدعاء!!
    من واجهوا كيد الأعادي بالتناحر والجفاء !!
    فلنأخذ بالأسباب ولنتوكل على الله
    وبإذن الله لن نرد خائبين

  3. [3]
    حليمه..........
    حليمه.......... غير متواجد حالياً
    جديد


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    اختي المتوكله على الله اشكرك على هذا الموضوع الجيد مما زاد من معرفتي في هذا المجال ولكن يوجد لدي سؤال اخر
    وهو ماافضل برنامج يمكن ان يستخدم في هذه الحاله اقصد التحكم بسرعة المحرك

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  4. [4]
    ENG_ASHRAF
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    عضو متميز


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    جزاكم الله خيرا

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  5. [5]
    بكار الوديدي
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    عضو


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    جزاكم الله خيرا

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  6. [6]
    ابو عبد اللطيف
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    السلام عليكم يااخت حليمه
    هناك طرق كثيره فى التحكم فى induction motor
    ارجوا ان تمهلينى اياما لتوفيرها
    لأن مشروع التخرج كان متخصّص فيها
    ابشرى ان شاء الله

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  7. [7]
    aattaa
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    عضو فعال


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    تحياتي الى جميع المشاركين

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  8. [8]
    حليمه..........
    حليمه.......... غير متواجد حالياً
    جديد


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    case study

    السلام عليكم اخواني عساكم بخير بالنسبه لهذا الموضوع ارغب في التعاون معكم لايجاد case study في التحكم بسرعة المحرك عن طريق الfreqyency drive وسأكون لكم من الشاكرين.

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  9. [9]
    ابو عبد اللطيف
    ابو عبد اللطيف غير متواجد حالياً
    عضو


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    e=حليمه..........;السلام عليكم اخواني عساكم بخير بالنسبه لهذا الموضوع ارغب في التعاون معكم لايجاد case study في التحكم بسرعة المحرك عن طريق الfreqyency drive وسأكون لكم من الشاكرين
    اليك هذا البحث أن شاء الله تستفيدى منه

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    الملفات المرفقة

  10. [10]
    مصطفى ابو الحارث
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    جديد


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    شكرا
    جزاك الله خيرا بس بدنا معلومات اكثر

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