| 摘要 |
708,857. Supply systems depending on two sources. PERKINS, Ltd., F. May 8, 1952 [Dec. 3, 1951], No. 28306/51. Class 38(4) An arrangement for preventing the connection of an induction generator (not shown), to an existing mains supply when the speed of the machine is not within predetermined limits, comprises a tachometer generator G driven with the machine and controlling relays A-C, of which B and C have contacts in series with the operating coil H of a contactor K by which the machine is connected to, or disconnected from, the mains. When the machine is run up from standstill a signal lamp AM is energized from the mains over the back contact A1 of the relay A until a predetermined lower speed limit (determined by resistor D) is reached: the output from the tachometer generator is then sufficient to operate relay A which then interrupts the circuit of lamp AM and energizes relay B from the mains over contact A2. Operation of relay B inserts an economy resistor E in series with relay A, connects an over-speed relay C to the tachometer generator, energizes a signal lamp GN and, subject to closure of a manual switch J energizes the coil H, thus connecting the machine to the mains. If the speed of the machine rises above a predetermined upper limit (determined by resistor F) relay C operates to disconnect the machine by interrupting the circuit of coil H at contact C1 and to energize a signal lamp RD over contact C2. The arrangement is such as to provide a small and substantially constant load on the tachometer generator.
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