GB1035641A - Improvements in or relating to phasing apparatus - Google Patents

Abstract

1,035,641. Automatic speed control. DOWTY ROTOL Ltd. Jan. 9, 1963 [Jan.10, 1962], No. 992/62. Heading G3R. Master and slave alternators are provided with pulse generators 1,2, each affording a pulse when its associated shaft passes through a predetermined position, the pulses being passed through squaring and shaping circuits 4, 5, the mean output levels of which are proportional to the pulse frequency of its associated generator. The outputs of the circuits 4, 5, are subtracted from each other to provide a speed error signal which is fed through a smoothing and phase correction circuit 6 to a D.C.amplifier 7 actuating an electrohydraulic servo valve 8 which controls jack 9. A speed control lever 14 of the engine which drives the slave alternator is coupled to the jack 9, and a positional feed-back circuit 13 operates so that the displacement of rod 12 is proportional to the controlling signal. The pulse output of generators 1, 2, are also fed to a bi-stable circuit 3 whose output has a mean level proportional to the phase difference between the generators. The output of the circuit 3 is added to the speed error signal and supplied to integrating amplifier 17 which provides an output only when the speed error signal falls below a predetermined value. The output of the amplifier 17 is connected to the input of the amplifier 7, the lever 14 being controlled so that the speed error and phase error are reduced to zero, and the desired angular phase relationship is maintained between the alternators. The servo valve 8 has inlet 21 connected to hydraulic power supply unit 20. A vane 26 between nozzles 22,23, is controlled by coil 27 connected to amplifier 7. If the signal moves the vane towards nozzle 22, spool 28 is moved to the left so that the jack 9 likewise causes movement of rod 12 towards the left. A driver stage 18 is responsive to the output of circuit 3 which detects when the speed error and phase error of the slave alternator are within predetermined limits and allows relay 19 to switch the slave alternator into circuit with the master alternator. The circuit 3 may be replaced by a device having four stable states, whereby the device is tripped between the third and fourth states, providing maximum output, when the master frequency exceeds the slave frequency. When the slave frequency predominates, the device is switched between tween minimum and maximum output conditions.