| 摘要 |
1,116,710. Control of D.C. motors. TEXTRON Inc. 1 Dec., 1966 [29 Dec., 1965], No. 53861/66. Heading H2J. [Also in Division H3] A D.C. motor 20, e.g. of printed circuit, permanent magnet type, for positioning carriages on a machine tool is energized from an A.C. source via back to back thyristors 52, 53, both of which are triggered in respective half cycles but the firing angle of one is advanced with respect to the other to determine direction and speed of operation. The triggering signals are produced by relaxation oscillators coupled by transformers T1, T2, and comprising unijunction transistors 63, 64 which conduct when the voltage on capacitors 70, 71 reaches an appropriate level; the capacitors are charged from a constant current circuit 75 but the rate is modified by a differential transistor amplifier 84, one side of which 86, is connected to earth while the other 85 receives a control signal from a summing circuit 37. This control signal comprises a command signal from a programmer, fed through an operational amplifier 130, with stabilizing feedbacks from a tachometer and a low pass filter 41 receiving armature voltage. Another filter network 110 provides phase correction. The oscillators are synchronized with the A.C. supply by a circuit 150; this provides a ramp voltage to the unijunction transistors which provides a low impedance path to -28 v. at the end of each half cycle. |
