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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
    It's OK, my numbers were not quite the same as his either, your track is correct.


    500RPM is  8.3 revs second.

    Each rev is equivalent to a 40N force sweeping a full circle of 1m radius, so 6.2 metres *40N =  call it 250 joules per rev.

    But there are 8.33 rev/second  - 2010 joules per second = watts 

    call it 2 kilowatts of mechanical work.


    Now  5 of the volts are thermal the rest is the magnetic forces of the self generated opposition due to the rotation, so 

    2000 watts, 115V  (right - this is not that realistic ) 17.3 amps.

    So the armature resistance is 5V/17A =  ~ 0.33 ohms





Reply
  • 0
    It's OK, my numbers were not quite the same as his either, your track is correct.


    500RPM is  8.3 revs second.

    Each rev is equivalent to a 40N force sweeping a full circle of 1m radius, so 6.2 metres *40N =  call it 250 joules per rev.

    But there are 8.33 rev/second  - 2010 joules per second = watts 

    call it 2 kilowatts of mechanical work.


    Now  5 of the volts are thermal the rest is the magnetic forces of the self generated opposition due to the rotation, so 

    2000 watts, 115V  (right - this is not that realistic ) 17.3 amps.

    So the armature resistance is 5V/17A =  ~ 0.33 ohms





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