| 摘要 |
<p>1,150,903. Control of D.C. motors; rectifying. WARNER & SWASEY CO. 20 May, 1966 [24 May, 1965], No. 22483/66. Headings H2F and H2J. [Also in Divisions G3 and H3] In a system wherein the mean current supplied from an A.C. source to a D.C. motor is varied by varying the firing angle of a thyratron or thyristor in the supply circuit, triggering is effected by a plurality of pulses when the magnitude of a cyclically varying control signal reaches a predetermined threshold level. The output 26a of a tachogenerator which may be A.C. or D.C., is amplified by transistors 90 ... 92 and mixed with a bias signal 30 which is A.C. at mains frequency. The result varies the conduction of a transistor 64 and hence the current through a tunnel diode 70; at a particular level this switches to its non-linear condition and causes conduction of a further transistor 66, the resulting output pulse being differentiated and converted to a pulse of constant length at 75, which is applied as one input to a gate circuit 34. A second input is from a continuously running transistor oscillator 36, whose pulses are thus passed to an amplifying and pulse shaping stage 38 to trigger the thyratron 50 or thyristor (111, Fig. 3, not shown). The pulses are of relatively high frequency so that if the first fails to trigger another rapidly follows. For reverse rotation an oppositely poled thyratron 51 or thyristor is triggered by a separate circuit; the bias signal is applied to both circuits with 180 degrees phase difference so that the error signal effectively phase advances the bias to the circuit for appropriate direction of rotation.</p> |
