Introduction:
In a DC machine, the winding is responsible for generating the magnetic field required for the operation of the machine. There are different types of winding arrangements used in DC machines, such as lap winding and wave winding. Each winding type has its own advantages and is suitable for specific applications.

Lap Winding:
Lap winding is a type of armature winding employed in DC machines. In this winding arrangement, the armature coils are connected in parallel and are connected to form a closed loop. The number of parallel paths is equal to the number of poles in the machine. Lap winding is commonly used in DC machines for high current and low voltage applications.

Explanation:
- High Current: Lap winding is suitable for high current applications because the parallel connection of armature coils allows for the division of current among multiple paths. This helps in reducing the current density in each coil, preventing overheating and ensuring the machine's efficient operation.
- Low Voltage Rating: Lap winding is suitable for low voltage applications because the parallel connection of armature coils results in a lower voltage drop across each coil. This helps in minimizing power losses and ensures that the machine operates within its voltage rating.
- Advantages: Lap winding provides better cooling due to the parallel paths, reduces the chances of short circuiting, and enables easy repair and maintenance of the winding.
- Disadvantages: Lap winding requires a large number of turns, resulting in a longer winding length. This increases the size and weight of the machine and makes it more expensive to manufacture.

Conclusion:
In conclusion, lap winding is employed in a DC machine for high current and low voltage applications. The parallel connection of armature coils in lap winding allows for the division of current and reduces the voltage drop across each coil. This ensures the efficient operation of the machine and prevents overheating. However, lap winding is not suitable for low current and high voltage applications due to its inherent design characteristics.