sum of self induced
voltage, mutual voltage, and rotation voltage. As shown in Fig.
2, the rotating direction of DC-motor axis is assumed as
counterclockwise, the brush marked “+” is brush 1, and the
brush marked “-“ is brush 2. The branch circuit 1 is defined as
the flowing direction of current is from brush 1 to brush 2
along with clockwise direction. Comparatively, the branch
circuit 2 is defined as the flowing direction of current is from
brush 1 to brush 2 along with counterclockwise direction. The
flowing current and the resistance of all windings occurred on
the branch 1 is defined as i1 and r1 . Relatively, the same
parameter occurred on the branch 2 will be defined as
i2 and r2 . The rotating induced voltage of windings a , b , and
c are e1 , e2 , and e3 , respectively. Compared to the rotating
induced voltage of these armature windings, the values of self
induced voltage and mutual induced voltage are generally
lower than that of the rotating induced voltage. For simplifying
the analysis, the self and mutual induced voltages will not be
considered here. According to the Kirchhoff’s current law, the
current value of DC motor must copy with the
relationship i = i1 + i2 .