Hello everyone

I am not an expert in the Electrical machine. So, can anyone help me with this question?

If I have a 4 layer DC machine winding, should the number of commutator segments be 4 times greater than the number of armature slots, or there are some techniques to do that with a lower number of commutator segments?

 

In a DC armature there would typically be the same number of armature bar than coils.
In the simplest (simplex) form e.g In a nine coil armature there would be nine bars and each coil would span 5 slots, coil 1 slot 1 & 5, coil 2 slot 2 & 6 etc, etc.
There is also the duplex and triplex, lap winding method, but you would need to know the original design of the motor to ascertain which was used.
If you wish to delve into it further, I recommend the "Electric Motor Repair" by Robert Rosenburg, which is still considered the 'bible' on motor winding.
Max.