Abstract: A small motor having a planar air gap has a rotor comprising a rotor shaft journalled in a carrier pipe of small diameter at whose outer periphery are mounted shape-retaining rotor coils which are cantilevered out into the air gap. This provides a rotor of very small axial moment of inertia, affording very short start-up times. Furthermore, the coils are subjected to very good cooling action. Such a motor is suitable especially for signal-recording or -reproducing apparatus. The arrangement of the rotor coils is symmetrical and yields a very simple and compact motor construction.

Abstract: To reduce a unidirectional leakage flux emanating from a two-filament, pulse-energized motor, the stator (21, 22) is constructed at least as a four-pole stator and each filament (40, 41) of the windings (45; 74, 75, 78, 79) associated with respective stator poles is wound on the stator core elements (21) such that the number of North poles and South poles arising at the circumference of the core elements, upon energization by a current source (48, 49) of the respective filaments, will be identical, and the sum of the magnetic flux due to the energization of the respective filament arising, for example, at the center or shaft of the motor, will be essential zero, so that the effect of unidirectional, pulsating leakage flux upon a galvano-magnetic sensor (16) or other magnetic apparatus, e.g. magnetic tape transducing devices, will be essentially eliminated.

Abstract: To prevent damage to magnetic storage disks from sliding of the magnetic heads over the disk surface during running-out of the disk to a stop, the disk is positively braked when its drive is de-energized, so as to shorten the running-out time.

Abstract: A motor for direct or coaxial drive of a disc storage, mounted in a center hole formed in a storage disc includes a rotor and a stator which form together with an air gap separating the rotor from the stator a magnetic circuit. The stator has a single-phase winding. The motor produces an auxiliary reluctance moment complementing the electromagnetic torque produced by the winding and being offset in time relative to the electromagnetic torque. Due to the positioning of the motor within the center hole of the disc a very compact construction is obtained.