DC generator wiring theory - basics

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Joined Sep 12, 2015
Given a simple DC generator with a single loop in the presence of a magnetic field such as the one below, typically, the analysis involves how each rectangular loop's terminal ends up on opposite sides of an armature housing each of the coils.

A split ring (in yellow attached to the gray brushes) rectifies the generated current by always ensuring that the positive terminal of the generator is in contact with the left brush, which taps of the electrical energy. If this isn't clear, consider in which direction current flows and that current flows from a place of high potential to a place of low potential.

The analysis is fairly straightforward to then extend to a second loop positioned perpendicular to the first loop. The result is also a rectified / pulsed DC waveform at the brushes, except there will be a more regular supply of pulses than in the case with one loop. The two coils are connected to a commutator such that opposite ends of each loop's terminals go to opposite ends of the commutator. This is conceptually straightforward as well.

All of this is fine, but in real life, generators with many such armature windings / loops are wired such that the opposite ends of a loop are connected as follows.

In other words, given 6 loops, instead of the first loop having one end at 12 o'clock on a clock and the other end at 6 o'clock on a clock (opposite ends with respect to the center), the ends are at 12 o'clock and 1 o'clock (adjacent).

Can someone help me understand why? How does the analysis change, if at all at that point, as far as how much voltage is generated?

Thank you all for this wonderful resource and thanks for your time.


Joined Jul 18, 2013
Fig 1.8 of the pdf nsaspook has shown explains the distortion of the waveform and displaces the neutral point which the armature moves toward but never reaches in motor mode.
In the case of generation, the armature coils cut through the Field poles at the strongest point.