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Course work help

Daniel S Robinson
Hi

I was wondering if some one could help me with my assignment.

Normally I wouldn't ask but I'm struggling to find a formula

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I'm stuck on the 1st question, I have found two formulas   I= Tω/V   and  Ea = 2πNT/Ia   re aranged   Ia = 2πNT/Ea

Both give different answers and don't take into account the back EMF.


Can any one give me some pointers please. I have looked through all my books but can't find any answers.

Any help would be appreciated.

Thank You

Daniel Robinson


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  • 0
    Hi Daniel,


    The two formulae are essentially the same. Going to first principles, the mechanical equation for power is P=ωT where ω is the angular speed. Substituting the electrical equation P=VI we get VI=ωT which can be rearranged to I=ωT/V (formula 1). Since ω=2πN where N is the number of rotations per second it can be restated as I=2πNT/V (essentially formula 2 if you use armature current and armature voltage).


    If you get different answers then perhaps you should look at the numbers you are putting in to the equations to see where the problem is. Hope this helps to get you started - if you still have problems come back for further help.
Reply
  • 0
    Hi Daniel,


    The two formulae are essentially the same. Going to first principles, the mechanical equation for power is P=ωT where ω is the angular speed. Substituting the electrical equation P=VI we get VI=ωT which can be rearranged to I=ωT/V (formula 1). Since ω=2πN where N is the number of rotations per second it can be restated as I=2πNT/V (essentially formula 2 if you use armature current and armature voltage).


    If you get different answers then perhaps you should look at the numbers you are putting in to the equations to see where the problem is. Hope this helps to get you started - if you still have problems come back for further help.
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