How to solve this problem?

Discussion in 'Homework Help' started by lihker, Dec 3, 2008.

  1. lihker

    Thread Starter New Member

    Dec 3, 2008
    3
    0
    The unipolar drive circuit of a three phase variable reluctance stepper motor used for positioning a valve is shown in circuit.JPG

    The motor has the following parameters :
    Winding resistance (RW) = 0.6 Ω Winding inductance (LW)=0.24 mH.
    Rated current = 5 A he stepping rate = 450 steps/sec

    Design the drive circuit such that the electrical time constant is 1.5 ms at turn-on and 0.8 ms at turn-off.

    We want to find out the R(ext) value using T (on)=Lw/Rw+R(ext)
    But after i calculate R(ext)=-0.44Ω(resistance do not have negative value) something wrong!!

    somebody help me solve thank
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Are you sure about the values?
     
  3. lihker

    Thread Starter New Member

    Dec 3, 2008
    3
    0

    the value is correct
     
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