| 摘要 |
1,056,874. Inverting; control of A.C. motors. M. ETTER. Aug. 12, 1963 [Aug. 13, 1962], No. 31719/63. Headings H2F and H2J. In a polyphase inverter comprising a bridge of controlled rectifiers 5, 6 fed from a D.C. supply a, b, and feeding a motor M, control means are provided so that the current waveform attains a desired shape, preferably a sinusoid. With a rectifier 5 conducting a median point 8 is at the positive supply potential, and with a rectifier 6 conducting it is at earth; also diodes 3 and 4 carry provide for the continuance of current when a rectifier shuts off. It is therefore possible to have any desired mean potential for the point 8. Inductors and diodes 44-47 are provided to take up current surges on switching. The switching off of a rectifier is effected by firing two series rectifiers 5, 6, together so as to charge a resonant circuit 50, 51 or 52. The discharge of this circuit through the rectifiers shuts these off. Firing signals are derived from an oscillator 33 (at, say, 3000 c/s.) through a ring-counter 54 giving pulse signals Bi, Bj, Bk, at a signal frequency of 1000 c/s. These signals (Fig. 2d) pass to control units 55, 56, 47, which route each signal to either rectifier 5 (Fig. 2e) or rectifier 6 (Fig. 2f) in order to control the current so that this tends to follow a desired sinusoidal waveform. This routing is effected as follows:- The actual phase current I r (Fig. 2a) is compared with the current a of a sinusoidal source 61 of 1000 c/s. in saturable cores 58, 59, 60. Whenever these current waveforms cross a short pulse is produced (due to reversal of the magnetization) whose sign depends on whether I r is becoming larger ( + ve) or smaller ( - ve) than a (Fig 2b). These short pulses are applied to the units 55, 56, 57, wherein further pulses are produced which are started by a positive short pulse and terminated by the next negative short pulse (Fig. 2c). If the pulses Bi from the ring counter arrive during the presence of a long pulse it is routed to rectifier 6; if, however it arrives during an interval between pulses it goes to rectifier 5. The routing circuitry comprises a transistor arrangement (Fig. 3, not shown). |
