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  • Questions about DC Machines

    sreekant

    Member

    Updated: Oct 25, 2024
    Views: 1.0K
    what is the relation between speed and armature current?,flux vs armature current?what happens to flux,armature current,speed,torque if the load increases??
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  • AMITBOSE

    Member • Sep 2, 2009

    Re: dc machines

    U can refer ashfaq hussain book
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  • vishnu priya

    Member • Sep 2, 2009

    Re: dc machines

    AMITBOSE
    U can refer ashfaq hussain book
    More details please!!!
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  • Mr.Don

    Member • Sep 2, 2009

    Increase in flux decreases the speed but increases the torque. If torque is decreased by decreasing the field current the following sequences are found:

    1. <a href="https://en.wikipedia.org/wiki/Counter-electromotive_force" target="_blank" rel="nofollow noopener noreferrer">Counter Electromotive Force</a> drops instantly, the speed remaining constant because of the inertia of heavy armature.
    2. Due to decrease of EMF armature current I is increased because of I = (V − E)/R.
    3. A small decrease of flux is more than counterbalanced by a large increase of I which means net increase of torque.
    4. If torque increases the speed also increases.
    If applied voltage is kept constant, motor speed has inverse relation with flux.
    [​IMG] where:

    • N = revolutions per minute .i.e. motor speed
    • K = proportional constant
    • R = resistance of armature (<a href="https://en.wikipedia.org/wiki/Ohm" target="_blank" rel="nofollow noopener noreferrer">Ohm</a>)
    • V = electromotive force (<a href="https://en.wikipedia.org/wiki/Volt" target="_blank" rel="nofollow noopener noreferrer">Volt</a>)
    • I = current (<a href="https://en.wikipedia.org/wiki/Ampere" target="_blank" rel="nofollow noopener noreferrer">Ampere</a>)
    • Φ = flux (<a href="https://en.wikipedia.org/wiki/Weber_%28unit%29" target="_blank" rel="nofollow noopener noreferrer">Weber %28Unit%29</a>)
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  • Mr.Don

    Member • Sep 2, 2009

    You will know it clearly by doing lab exercises perfectly..
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  • ashutoshglamour

    Member • Sep 3, 2009

    You can find the answers in book-B.L.THEREJA
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  • cowboy

    Member • Sep 3, 2009

    I can find answer in any electrical machine book like b.L.Thareja volume 2.
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