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    Electrical Energy Conversion - Rotation, Resistance and Speed

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    DC Machines

    A 300 hp, 500 V, 1750 rpm DC shunt motor, operating at rated conditions has an efficiency of 92.0 percent... (see attachment)

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    1. Equivalent circuit for DC shunt motor:

    Where Ra is armature resistance Ra = 0.042 Ohm
    Rf is field resistance Rf = 86.2 Ohm
    U1 is the input voltage U1 =500V
    Ea represents armature m.m.f.
    Ia is armature current, If is the field current, and I1 is the motor input current

    2. Rotation losses

    The motor is running at rated conditions, so the output mechanical power is 300HP.
    1HP = 746W
    The output mechanical power P2 = 300*746 = 223800 W =223.8 kW
    The efficiency ...

    Solution Summary

    This solution is provided in 406 words in an attached .doc file. It includes a diagram of the DC shunt motor, as well as calculations for rotational loss, external resistance, and speed.