| 摘要 |
PURPOSE:To provide an appropriate method for driving a record player or the like, by partially or entirely disconnecting a driving winding from an AC power source when a running speed exceeds a prescribed value and by applying DC power to the driving winding to perform eddy current braking. CONSTITUTION:An electroconductive ring 11 is provided on the periphery of a turntable 1. Main magnetic poles 3 and auxiliary magnetic poles 4 are alternately placed outside the electroconductive ring 11. Windings 31, 41 are provided around the magnetic poles 3, 4. When AC power is applied, a current flows through a main circuit winding 310 and a phase-advanced alternating current flows through the auxiliary winding 41 and a phase lead capacitor C. As a result, a forward and a backward eddy currents different in phase by 90 deg. flows in the electroconductive ring 11 and the turntable 1 is started by the action of magnetic fields due to the eddy currents. When the speed of the turntable reaches a prescribed level, switches S1, S2 are changed over and the current flowing through the main winding circuit is cut off and a direct current flows to perform braking action. When the speed falls, an alternating current flows again through the main winding and similar control is effected. |
