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Extract the angle polar numbers

  1. Jan 5, 2012 #1
    hi

    can anybody advise on this, need to find the angle out of the following

    2300=2000+(0.5<x).(4<90)

    got as far as

    300/4<90 = 0.5<x

    = 75<90= 0.5<x

    is this correct and anybody able to finish this off

    regards
     
  2. jcsd
  3. Jan 5, 2012 #2

    Mentallic

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    Homework Helper

    What is 4<90 and 0.5<x ?
     
  4. Jan 5, 2012 #3
    I think he means polar notation

    a [itex]\angle[/itex] ω = a ( cos ω + j . sin ω )

    but the OP formula seems to have a typo of some kind; the only expression I can imagine that makes sense is this

    2300 = 2000 . ( 0.5 [itex]\angle[/itex] x ) . ( 4 [itex]\angle[/itex] 90 )
    = 2000 . 0.5 . 4 cos ( 90 - x )

    x = 35.0996°

    May be that, or not...
     
    Last edited: Jan 5, 2012
  5. Jan 6, 2012 #4
    hi yes it is polar notation, got my notation and common sense mixed up (late one last night)

    the equation repersents the excitation current angle of a sychronous generator, ( Ia ∠ x ) stands for stator amps at some angle

    (2300∠ 15 ) = (1154.7∠ 0) + ( Ia ∠ x ) . ( 4 ∠ 90 )

    can some check if

    ( Ia ∠ x ) = ((2300∠ 15 ) - (1154.7∠ 0) / ( 4 ∠ 90 ))

    = (305.4∠-61)

    can someone confirm this for me please, if im wrong please correct ?
     
  6. Jan 6, 2012 #5
    ah, it's Ia instead of 4... 4 would never get a valid value... that makes sense now; also, if I remember electrics right, you're doing a complex number multiplication, not a vector inner product... so ( a ∠ b ) . ( c ∠ d ) is (ab) ∠ (b+d)... instead of (ab) ∠ (b-d) as I wrote above

    so

    (2300 < 15) = (1154.7 < 0 ) + ( I < x ) . ( 4 < 90 )
    (2221.63 + j 595.28) - ( 1154.7 + j 0 ) = ( I < x ) . ( 4 < 90 )
    (1066.93 + j 595.28 ) / ( 4 < 90 ) = ( I < x )
    ( 1221.76 < 29.16 ) / ( 4 < 90 ) = ( I < x )
    ( 305.44 < -60.84 ) = ( I < x )

    it looks good; confirming result with my trusty Texas calculator:

    (2300 < 15) = (1154.7 < 0 ) + ( 305.44 < -60.84 ) . ( 4 < 90 )
    (2300 < 15) = (1154.7 < 0 ) + ( 1221.76 < 29.16 )
    (2300 < 15) = (2299.99 < 15)
     
  7. Jan 7, 2012 #6
    thanks for that


    regards
     
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