When one brush is connected to one commutator and the other to the second the current from one brush goes through the rotor winding to the other brush in one direction and visa versa. This part i understand. But what happens when the brushes touch both parts of commutator at the moment when the commutation occurs? Doesn‘t this create some sort of short circuit between two brushes through the commutators without current going through the coil?
It's a good question, but it is a serious problem only when there are only 2 poles. All practical motors, from the smallest to the largest have more than that, so 2 adjacent poles will be connected to one side and their opposites to the other side. There will never be a short circuit.
