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stator poles is 90 .
Also, as you can see from the figure, in a DC machine the
armature is usually on the rotor, and the field winding is on the
stator.
DC motor parts
Figure 3.3 - DC machine
To keep this torque angle constant as the rotor spins on its shaft,
a mechanical switch, called a commutator, is configured so the
current distribution in the rotor winding remains constant, and
◦
therefore the rotor poles are consistently at 90 with respect to the
fixed stator poles.
In a DC machine, the magnetizing current is DC, so that there is
no spatial alternation of the stator poles due to time-varying
currents.
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