A brushless d.c. motor having a stator including a stator core with a plurality of Y-shaped magnetic poles. The magnetic poles have a first portion which extend radially outwardly from a hub portion of the core, second portions which extend from an outer end of the first portion in the opposite circumferential directions and third portions that extend from a tip of the second portions to the radially outer direction. A first stator windings are wound on the first portions of the magnetic pole and serially connected to each other for each of the magnetic poles, and second windings are wound on one of the third portions and the adjacent third portion of the contiguous magnetic pole, and serially connected to each other. The phases of the stator windings are shifted relative to each other.

A turntable speed lock system is provided to supplement an inexpensive main motor which drives the turntable through a pulley-belt arrangement, and which main drive arrangement fails to maintain the turntable rotation at a predetermined speed within specified tolerance limits desired for proper operation. A rotor ring, having a plurality of permanently magnetized poles of alternate polarity along its periphery, is mounted concentrically on the turntable for rotation therewith. A stator assembly including a core with an airgap, for receiving the rotatable rotor ring, is fixedly mounted on a turntable mounting plate. The stator assembly further includes a field winding for establishing an alternating field across the airgap. The magnetized poles freely pass, a seriatim, through the airgap when the turntable-mounted rotor ring is rotated by the main motor. The rotor ring and stator assembly function as a synchronous motor wherein the reluctance across the airgap is minimum when the turntable-mounted rotor ring is rotating at the predetermined speed, thereby locking the turntable to rotate at the predetermined speed within the specified tolerance limits.

Disclosed is a turntable apparatus which comprises a plurality of magnets provided on the inner surface of the turntable so as to be disposed in a state alternately opposite in polarity and a plurality of coils provided on a stationary substrate disposed to face said turntable, in a manner that the disposition of said plurality of coils is in corresponding relation to the disposition of said plurality of magnets, whereby said turntable is rotated by the electromagnetic force between said coils and magnets. There is provided on said stationary substrate position detecting means for detecting the electromagnetic position of the magnets relative to the coils. The output signals from said position detecting means vary in level with a magnetic field variation due to the rotation of the turntable. There is provided means for controlling supply of a DC current to each coil upon receipt of an output signal from said position detecting means thereby to cause a rotating magnetic field to be produced in the coils. Further, there is provided means for operatively comparing a specific reference voltage with that inductive voltage induced in the coil which is proportional to the rotation speed of the turntable, thereby to control supply of a current to the coil from a power source, thus to control the flow of current supplied from said power source to the coil, i.e., the rotation speed of the turntable.

A direct-driven type phonograph turntable has a frame, a main shaft, a rotor having a plurality of equally circularly spaced magnets on the periphery thereof and an arc-shaped stator having a plurality of inwardly extending, equally spaced teeth in opposed relation to the magnets. Static unbalances and preferably, also dynamic unbalances of the rotor are compensated for by an arcuate-shaped member of a magnetically soft material. The arcuate-shaped member is located at a substantially symmetrical position to the arc-shaped stator with respect to the main shaft. More exactly, and preferably, this member has end portions mutually angularly spaced by an amount equal to a plurality of the center-to-center spacings of the magnets plus one half of the center-to-center spacing of said magnets.

Gramophone turntable apparatus comprises a turntable with a hydrodynamic bearing so that, on rotation, the turntable is supported solely by a pressurized film of fluid. The bearing also supports the rotatable part of a turntable drive motor of rotary or linear form.