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What are the symbols in these electric motor equations?

  1. Jun 14, 2012 #1
    I'm revising for an exam and i’ve come across these equations in my lecture notes.
    Has anyone seen these equations before, and can tell me what the symbols represent?

    T = k1 ᶲ Ia

    Ea = k1ᶲ2πN = k2ᶲN

    Ea = Va-IaRa

    N = (Va-IaRa) / (2πk1ᶲ)

    Im guessing T is torque, Ea is the volatge across the motor, and Va is the source voltage. Im not sure though.



    The π symbol is pi
  2. jcsd
  3. Jun 15, 2012 #2
    T is torque.
    Ea is internal EMF
    Va is terminal voltage
    Ia is armature current
    N is rotor speed (probably in rpm)
    Uppercases Phi Φ is flux due to field current.
    k1 is a constant
  4. Jun 15, 2012 #3
    Thanks, can i just ask, what do you mean by armature current? Is this just the current through the motor? Also what do you mean by internal EMF?
  5. Jun 15, 2012 #4
    Yes, its "just" the current through the motor. More specific, the current through the armature winding. Internal EMF is the electromotive force due to rotating magnetic field, faradays law etc....

    Formulas do you no good if you dont know the basis and derivation of them. I would suggest reading the course book in order to get the basic understanding of electromagnetism and DC motors.
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