Which of the following are DC windings?

Correct option is D

DC Windings: DC windings are used in the armature of DC machines (motors and generators) and are designed to produce a uniform magnetic field distribution and ensure proper commutation.

Lap Winding : Lap winding is a type of armature winding commonly used in DC machines.

In this winding, the end of each coil is connected to the start of the next coil in such a way that its "laps" back over the previous winding.

This type of winding is particularly useful for machines that require high current and low voltage, as it allows for more parallel paths for the current, thus reducing the resistance.

In this type of winding, the number of parallel paths is always the number of poles and the number of brushes.

​$$A = P \\\text{where,} \\A = \text{No. of parallel paths} \\P = \text{No. of poles} \\$$

In a lap winding for a DC machine, the number of poles is equal to the number of brushes. This is a fundamental characteristic of lap winding.

$$\frac{\text{number of poles}}{\text{number of brushes}} = 1 \\\bullet\ \text{This winding is used for high-current, low-voltage DC machines.}$$​​​