If at a certain point the action of the motor moment should cease and the current remain unchanged, since the excitation is in series, the magnetic field would also remain unchanged and the machine, subject only to the action of the electromagnetic moment, would invert the direction of rotation. Thus if current is applied to the machine in the same direction in which it circulates when it works as a dynamo it begins to work as a motor, but rotation in the opposite direction. Obviously, to make Pacinotti's machine work as a motor it is necessary to exclude the super exciter and, to maintain the efficacy of the residual magnetization the current must maintain the same value at all times.