the funnel 14 the center of gravity of the rotor is not located exactly on the axis of symmetry 8 the rotor can still rotate about its largest central principal axis of inertia adjacent axis 8 because of the floating bearing which is provided as above described thereby preventing creation of additional bearing forces the importance of the construction of the drive motor as an iron free electric motor is then enhanced in that it also ensures that no additional radial forces or moments are exerted on the bearing even by the drive itself that is to say even if the rotor does not rotate exactly about the axis 8 in order to reduce drive losses due to the air resistance which occur particularly at high speed the rotor is surrounded on its outside by a stationary housing 18 assuming that the windings 19 have the form of a three phase winding the three phases are connected in succession to d c power source 21 by means of a commutating switch 22 for reasons of simplicity only the conductor pair for one winding phase is shown connected to the switch the commutation operation of switch 22 is well known in the art and will not be explained in detail here a resistor 23 is connected into the current input lead from source 21 and a voltage proportional to the supply current is derived therefrom if the reaction torque on the motor changes due to the occurrence of.