| 摘要 |
<p>1,100,280. Control of A.C. motors. OXYMILL S.A. 29 Sept., 1966 [30 Sept., 1965], No. 43659/66. Heading H2J. [Also in Divisions G3 and H3] The field windings 2, 3 of a synchronous motor 4 are supplied at a variable frequency for continuous operation in either direction through a null position, a generator 5 supplying pulse trains to gates 6-9 which are also controlled by generator 10 having a fixed frequency F. The outputs of the gates are connected to amplifiers 11, 13 and 12, 14 associated with the field windings 2 and 3 respectively. The pulse trains from the generator 5 are mutually phaseshifted and have a frequency of F+f, where f is the variable frequency of a control signal applied to terminal A. Each gate has a storage unit and transmits samples of the waveform from the generator 10, the output of the gate being formed by the envelopes of the sample signals, such envelopes being in the form of half sine-waves having a frequency equal to f. Half-waves, which are phase-shifted by one half-cycle, are applied to the winding 2 to reconstitute a full sine-wave at the terminals of the winding, the winding 3 similarly receiving a second full sine-wave which is retarded in phase with regard to the first. The motor is reversed when the frequency of the pulses from the generator 5 is changed to a value less than F. When the control frequency is zero, the motor receives direct-current to hold it in a well-determined position. Each gate comprises switching transistors 15, 16 which transmit the waveform applied to terminal D only during delivery of pulses applied to terminals B, C. Capacitor 19 is charged by each of the successive sample signals, the charge remaining constant between two samples so that the output voltage at terminal S has a step shape which approximates to the waveform to be transmitted. The servomotor may carry out a sequence of movements according to a set programme, the control signal applied to the terminal A being a positional error signal. A magnetic tape 20 records a signal having a frequency which is multiple of F+f, as well as the reference signal having frequency F, whereby the programme can be reproduced by means of reader 21.</p> |
