| 摘要 |
1,120,101. Control of A.C. motors. EUGEN BAUER G.m.b.H. 16 July, 1965 [18 July, 1964], No. 30213/65. Heading H2J. [Also in Division G2] The A.C. motor 12 driving the film transport mechanism of a cine projector is rapidly halted electromagnetically by the discharge of a D.C. pulse from capacitor 33 into the stator windings of the motor by means of switch 24, actuated by a main relay 39, which, in its normal position, closes the A.C. supply circuit to the motor. The relay simultaneously actuates switch 28 to send a direct current at a lower voltage than the braking pulse into the stator windings to hold the motor in its arrested position. Correct phasing of the discharge with motor supply is obtained by means of rectifiers 43, 44 in the lead 38 from winding 36 of transformer 19 to relay 39. The relay actuating current is supplied from rectifier 43 at a higher voltage in one half-cycle, and a lower voltage relay holding current is supplied from rectifier 44 in the other half-cycle. The motor holding current circuit also opens switch 35<SP>1</SP>, whereby the main relay 39 may only be energized through switch 15 which is operated in synchronism with the film drive by a cam 14, 46 on the motor shaft. Switch 15 opens during the film feed stroke of a Maltese-cross system so that motor 12 restarts at a lower voltage and moves until cam 46 releases the switch 15, when relay 39 operates again. Switch 40 which controls relay 39, may be actuated by a remote control device. |
