Page 626 - Basic Electrical Engineering

flowing through the winding have been shown by cross ⊗ and dot ⊙ A cross
indicates current flowing in the direction perpendicular to the plane of the
paper downwards and a dot indicates that current is coming towords the

observer looking into the paper.

Figure 7.15 Working principle of a dc motor illustrated

Figure 7.16 Coils 1−1′, 2−2′, 3−3′, 4−4′, 5−5′, and 6−6′ of the armature are shown connected in
series

There are six coils 1−1′, 2−2′, 3−3′, 4−4′, 5−5′, and 6−6′ placed in armature
slots. Current in coil sides 1, 2, 3, etc. are shown by cross and current at the

other coil sides, i.e., 1′, 2′, 3′, etc. are shown by dots. The flow of current
through the coils has been shown diagrammatically as in Fig. 7.16. By
applying Fleming’s Left-Hand rule, it is seen that force developed on the

upper half of the armature conductors in Fig. 7.15 is from right to left and for
the lower half of the armature conductors it is from left to right. These forces

lead to development of torque which causes rotation of the armature in the
anticlockwise direction as shown in Fig. 7.15. It may be noted carefully from