Patent GB-430008-A (GB)
Title: Improvements relating to electrical power systems
IPC: H02J1/16
Filed: 1933-12-04
Abstract: 430,008. Equalizing load on generators; converting. PESTARINI, G. N., 4, Tapton House Road, and TUSTIN, A., 22, Glentilt Road, both in Sheffield. Dec. 4, 1933, No. 34063. [Classes 38 (ii) and 38 (iv)] In a power system, a source of constant current is connected in series with a load and with a flywheel generator which is excited in accordance with the load voltage so as to equalize the load demand on the source. In a constant current system in which a " metadyne " type generator 2 supplies a load 1, load fluctuations above and below a predetermined value are taken up by a flywheel generator 6 in series in the circuit. The generator 6 has a field winding 10 providing constant excitation producing a motoring torque and a field winding 9 excited by the voltage across the load and producing a generating torque. The speed of the flywheel machine is limited by the provision of a generating field winding which is excited from a critically excited generator on the flywheel shaft. A relay may be provided for deenergizing the field windings when the speed of rotation of the flywheel is small or its direction reversed. Alternatively all the above compounding fields may be provided on an exciter supplying a single field winding on the flywheel machine. The flywheel machine may be of the " metadyne " type, its primary brushes being connected in the load circuit and its secondary brushes being connected to a field winding thereon which, under motoring conditions opposes the flux due to the windings 9 and 10 so that the motoring torque is decreased as the speed increases. In a further modification, Fig. 6, the primary brushes a, c of the flywheel " metadyne " machine are connected to a generator 16 on the same shaft which generator is excited by the field windings 9, 10 and the secondary brushes b, d are connected in the load circuit. In addition a field winding on the flywheel " metadyne " may be connected in the primary circuit thereof. Alternatively the flywheel " metadyne " may have its primary brushes connected to a generator having constant excitation and on the same shaft, and may have a winding, energized in response to the load, directly on its stator which is arranged to have high reluctance. In certain cases the winding responsive to the value of the load may be dispensed with, sufficient response being obtained from the inherent properties of the flywheel " metadyne " machine to maintain the secondary current constant. The constant current source may be a metadyne transformer or generator, or a machine comprising a main generator and a load current excited exciter therefor, or it may be a mercury vapour rectifier suitably controlled. In a modification the flywheel machine is arranged to have no action between two limits of load value and to carry the load peaks outside these values. This is obtained by exciting the flywheel machine in opposition by two field windings, one directly responsive to the load, and the other connected to an exciter excited in response to load values. These fields balance until, at a predetermined value the exciter saturates and the excitation directly responsive to the load predominates and produces the desired effect. The machine is also excited so as to produce a tendency to run at a particular speed, this may be obtained by providing a constant excitation and a field winding connected across the primary brushes on the flywheel metadyne machine when such is used, or alternatively the excitation indirectly responsive to the load may be arranged to overcome that obtained directly therefrom within the prescribed limits so as to produce a torque tending to maintain the flywheel speed constant. The above effects may be obtained from one main field winding energized from two opposed series connected exciters, one of which is arranged to saturate, both being excited in accordance with the load values. In a further modification the constant current source is a " metadyne " generator 45 driven from A.C. mains by a synchronous motor 46, an exciter 47 on the same shaft providing voltage for control and excitation circuits. A " metadyne " exciter 56 on the shaft of the flywheel machine has its primary brushes connected to an auxiliary generator 58 on the shaft of the motor generator 45, 46, which auxiliary generator is excited in accordance with the voltage across a winder motor 50 constituting the load and by an adjustable constant current in a winding 60. The field winding 51 of the motor 50 is energized from variable tapping points on a resistance 52 connected across the excitation supply and provides a gradual building-up of the load. A critically excited exciter 62 on the flywheel shaft produces a generating torque on the flywheel machine when its speed exceeds a predetermined value. A relay 66 responsive to the speed of the flywheel machine causes energization of a motoring field when the speed falls below a predetermined value. Regeneration in the load motor speeds up the flywheel machine to its upper limit and thereafter returns energy to the supply through the constant current motor generator, or other energy absorbing means may be provided. In a further modification the constant current source is a grid-controlled rectifier 74 connected to A.C. mains supply and regulated in accordance with the drop across a resistance 76 in series therewith so as to have a constant current output. In order to obtain greater stability of operation, a carbon pile regulator 79 controlled by the current in the load circuit operates on the excitation of a generator 58 which is also excited in accordance with the voltage across the load 50 and which is connected to the primary brushes of the " metadyne exciter 56 on the flywheel machine 49. The critically excited exciter 62 on the flywheel shaft also controls a relay 83 and on the flywheel attaining a predetermined speed connects the stator of an induction motor 81 on the flywheel shaft to the A.C. supply through a contactor 85, 86 so as to return power to the line during periods of light or regenerative load. A tachometer generator 91 on the flywheel shaft controls a relay 92 so that on the occurrence of a predetermined low speed a pole-changing winding on the stator of the induction motor 81 is connected to the A.C. supply through a contactor 98, 90 so as to maintain the speed of the flywheel from the A.C. supply during sustained overloads. Reverse power relays 89, 93 control the contactors 86 and 90 so as to disconnect the induction motor from the A. C. supply when power flows from or to the supply respectively. In a further modification the rectifier is not controlled and constant current is maintained in the circuit by a " metadyne " machine driven from the A.C. supply having its primary brushes connected across a source of constant voltage D.C. and its secondary brushes in series in the power circuit. The load-voltage controlled generator 58 which is connected to the " metadyne " exciter on the flywheel machine is also excited in accordance with the voltage across the series connected brushes of the constant current " metadyne " machine in order to secure greater stability of operation. Specifications 399,837 ; 404,739, [Group XXXVII], 417,517, and 420,770 are referred to, and the Provisional Specification refers also to Specification 417,381.