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The following test data was measured for a separately excited DC machine operating at a speed of $\\var{Ntest}\\ rpm$ with an open circuit armature:

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\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
 \nField Current\nIF [A]\n \n0\n \n0.1\n \n0.2\n \n0.3\n \n0.4\n \n0.5\n \n0.6\n \n0.7\n \n0.8\n \n0.9\n \n1.0\n \nArmature Voltage\nVA [V]\n {VA[0]} {VA[1]} {VA[2]} {VA[3]} {VA[4]} {VA[5]} {VA[6]} {VA[7]} {VA[8]} {VA[9]} {VA[10]}
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The intrinsic resistances are:

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Field Resistance: $R_F = \\var{RF}\\ \\Omega$

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Armature Resistance: $R_A = \\var{RA}\\ \\Omega$

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The machine is then connected as a shunt generator to supply $\\var{VL}\\ V$ to a $\\var{RL}\\ \\Omega$ load.

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What is the magnetism on the machine?

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$k_a \\phi =$ [[0]]

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• Find the field current, $I_F$, using Ohm's Law.
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• Find the speed and voltage during testing from the data at this field current.
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• Convert the speed from $N$ in rpm to $\\omega$ in rad/s.
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• Fill these values into $e_a=k_a\\phi\\omega$ to get the magnetism, $k_a\\phi$.
• \n
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How much current is it flowing in the armature conductors?

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$I_A$ = [[0]] A

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• Calcuate the field current, $I_F$, as before using Ohm's Law.
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• Calcuate the load current, $I_L$, using Ohm's Law.
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• Get the armature current from Kirchhoff's Current Law.
• \n
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At what speed is it running?

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N = [[0]] rpm

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• Calcuate the voltage, $e_a$, from Kirchhoff's Voltage Law.
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• Find the speed from $e_a=k_a\\phi \\omega$.
• \n
• Convert this to rpm.
• \n
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