| 摘要 |
953,940. Converting; control of A.C. motors. AMPEX CORPORATION. Jan. 31, 1962 [March 14, 1961], No. 3710/62. Headings H2F and H2J. [Also in Division H3] An inverter consists of a bridge of S.C.R.'s whose conduction periods are controlled by a pulse generator to produce an output waveform of predetermined frequency and harmonic content. As shown, Fig. 2, four S.C.R.'s 13, 14, 15, 16 are connected in a bridge circuit 27 and are controlled to produce the output waveform 40 across the load 17 from a D.C. source AB which may be the output of a rectifier 10 supplied from an A.C. source 11. Diagonally opposite pairs of S.C.R.'s 13, 15, and 14, 16 are alternately triggered into condition by pulses from a pulse generator, 19. Another S.C.R., 22, is arranged in a circuit with inductors 23, 24 and capacitors 12, 25, across the D.C. input to the bridge to provide a reverse transient to switch off the conducting elements of the bridge when S.C.R. 22 is triggered by a pulse from generator 19. In an alternative form, Fig. 3 (not shown), opposite pairs of rectifiers are controlled by alternate trains of three pulses supplied through transformers 68, 69, from a gating circuit 76 fed from a variable frequency pulse generator 78. When one pair of S.C.R.'s is conducting the first pulse of the next train fires the second pair of elements, thus short-circuiting the supply. A self-quenching circuit across the bridge input terminals, comprising inductors 51, 57, capacitor 58 and a diode 52, responds to this short-circuit by providing a reverse voltage to extinguish all bridge elements. The second pulse of the train fires the second pair of S.C.R's again and the third pulse is a timing pulse. D.C. may be applied to the load, e.g. to stop an A.C. motor, by operating a switch 79, which applies the generator pulses to S.C.R.'s 56, 62 only. The output waveform in both oases described is chosen such that it has no second or third harmonics or multiples of these. A gate circuit is described by means of which the alternate trains of three pulses can be obtained from the pulses supplied by the pulse generator, Fig. 4 (not shown). |
