3 Phase Question

Discussion in 'General Electronics Chat' started by shahin123, Sep 29, 2013.

  1. shahin123

    Thread Starter New Member

    Sep 3, 2013
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    Moderator Comment:

    This post tried to hijack Input current VS appliance rated current. It now has a thread of its own.

    One things i just don't understand we don't use Neutral in 3phase but we use neutral in 1phase motor. Any boy please explain me proper answer.
    Engineer Shahin.
     
    Last edited by a moderator: Nov 7, 2013
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Shahin, you have hijacked someone else's thread.
    If you are an Engineer I'm surprised you raised that question.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Post Hijack really, you should have posted separately.

    Is your 1phase derived from a 1ph transformer or from two phases of a the 3ph, or from one phase and the star point of the transformer?
    Earth Grounding any one side of any of those supplies makes it a neutral by definition, except the star point derived version, which is neutral by definition, and is usually earthed in most countries.
    Max.
     
  4. shahin123

    Thread Starter New Member

    Sep 3, 2013
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    I Have Three question all of my forum friends, Teacher, Engineer and others.
    1) Without motor pole, Name plate how i can find out motor RPM.
    2) Weight count Law.
     
  5. Alec_t

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    I've no idea what Q1 and Q2 are asking.
    Where is Q3?
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Without name plate how do you know voltage etc?
    Is this for 1ph or 3ph motor?
    There is a way but the above question needs to be answered?
    Max.
     
  7. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    The CEC doesn't agree. Neutrals don't exist in a 2 wire circuit. Although neutrals must be grounded if drawn out, this doesn't define it. Neutrals carry the imbalanced current in a multiple phase circuit, and yes, must be grounded if drawn out, otherwise they are bonded.
     
  8. gnuuser

    New Member

    Jan 17, 2013
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    most industry standard 3 phase motor rpm is usually 1725 to 1760 rpm.
    split phase motors may have 6 leads in the pecker-head that may be connected in two different configurations for 120/240 volt.
    while three phase motors will usually have a minimum of 9 leads which may be wired in different configurations for different uses
    but other than that info you cant judge the horsepower by size without a name plate.:confused:

    simply put if the motor does not have a name plate do not use it.:D
     
  9. tcmtech

    Well-Known Member

    Nov 4, 2013
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    Actually with three phase motors the electrical configurations and speeds can be all over the place.

    I work around industrial three phase gear fairly often and I see three phase motors with 8, 6, 4 and 2 pole configurations all the time.

    Lead count is similar. Multiples of three is about the only standard. I have 3, 6, 9, and 12 lead motors in my shop.

    Same with voltages. I have 200 - 230/400 - 460 VAC motors. 230 VAC only and a few 460 only motors as well.

    Also size has little consultancy with anything either. I have 3, 5, and 7.5 Hp motors that are all the exact same frame size too.

    Now if you really want to get complicated I also have a number of stock three phase motors in the 5, 7.5 and 15 HP ranges that run on normal 240 VAC single phase at their full rated power capacity through special converter units I designed for them.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I was indicating that in a two wire circuit there is no neutral unless one is earth grounded.
    The star point in a 3 phase transformer is neutral grounded or not.
    Max.
     
  11. shahin123

    Thread Starter New Member

    Sep 3, 2013
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    Excuse me i don't hijack any one post/ replay/ threat e.t c.
    i want just answer. because already i face many problem in my project.
    No body can help me here because i don't know.
    i have lots of question?
    1) Weight low in electrical/mechanical/civil engineering.
    2) what is the relation between Ampere, Voltage,Power factor.
    3) what is change over? why we use change over?
    Thanks
    Shahin
     
  12. shahin123

    Thread Starter New Member

    Sep 3, 2013
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    Yes Mr Max.
     
  13. strantor

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    Oct 3, 2010
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    Cannot. Hurdle. Language. Barrier.
     
  14. Alec_t

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    Sep 17, 2013
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    Your questions are not in clear English, but whatever they mean I think you could find the answers yourself just by googling the relevant keywords and phrases.
     
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