The armature winding consists of identical coils carried in slots that are uniformly distributed around the periphery of the rotor
Conventional DC machines are excited by direct current, in particular if a voltage-fed converter is used a dc voltage uf is supplied to the stationary field winding
Hence the excitation magnetic field is produced by the field coils
Due to the commutator, armature and field windings produce stationary magnetomotive forces that are displaced by 90 electrical degrees
Conventional separately excited DC electric machine
Using kirchhoff’s second law and assuming the differential equation of a generator
The steady state operating condition for a generator are
In generator application, the output is the voltage induced
24.
DC Machines Energy stored in inductor is stored in the magnetic field within the coil The mutual inductance between the armature and field windings
The armature and field magnetic axes are displaced by 90 electrical degrees and the magnetizing reluctance is constant
The Dynamic Equations (assuming r f ext = 0 ) are follows,
Where L ff = field self-inductance L fa = mutual inductance between the field and rotating armature coils e a = induced voltage in the armature coils (also called counter or back emf )
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