| 摘要 |
<p>1394731 Controlling maximum power demand of AC loads ST PAULS ENG CO Ltd and G D FORMAN 27 March 1973 [27 March 1972] 14168/72 Heading H2H Apparatus for distributing power from an A.C. source to consumer loads L1-L4 comprises triacs T1-T4 and a logic circuit for supplying pulses at the zero crossings of the A.C. supply to switch on, in a programmable sequence, the triacs selected by the operation of individual switches S1-S4 associated with the loads. The loads may be storage heaters, the hot plates of an electric cooker or industrial melting pots and the logic circuit prevents the simultaneous connection of, for example, two or more loads to the mains to restrict the maximum power demand. A pulse generator Y supplies pulses at the mains frequency to gates M1-M4 and a frequency dividing counter X, connected to frequency dividing counters W, supplies three out of phase pulse trains on leads t3-t5. A flip-flop F1 supplies anti-phase pulse trains on leads t1, t2 and a frequency dividing counter Z supplies four out of phase pulse trains on leads t6-t9. The pulse trains are fed to data selectors H1-H4 which also receive logical "1" or "0" signals on four further inputs depending on whether the switches S1-S4 are open or closed. The gates M1-M4 are connected to the trigger electrodes of the triacs via circuits X1-X4 provided with transformer or optical isolators. Alternatively the gates M1-M4 and the circuits X1-X4 may be replaced by integrated circuit, zero voltage switches. The outputs of the data selectors steer pulses from the generator 7 to the triacs so that if only one of the switches S1-S4 is closed, the associated gate M1-M4 triggers the associated triac continuously wheras if two or more of the switches are closed the associated triacs are triggered in sequence. Modifications are described in which the logic circuit includes a Mobius counter and in which the logic circuit includes a ring counter connected as a shift register. The triacs may be replaced by thyristors or thyratrons.</p> |
