Patent GB-434880-A (GB)
Title: Improvements relating to electrical power systems
IPC: H02J1/16
Filed: 1934-03-08
Abstract: 434,880. Equalizing load on generators. TUSTIN, A., 22, Glentilt Road, Sheffield, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. March 8, 1934, No. 7464. [Class 38 (iv)] A load 1, 2 is supplied from a generator 3 in series with a dynamo - electric machine 4 having a flywheel 6 coupled thereto and excited in accordance with the current in the circuit so as to maintain it at a set value. A field winding 7 on the machine 4 is excited from an exciter 8 on the same shaft, the excitation of which is obtained from a winding 10 carrying a constant current in opposition to a winding 9 carrying the load current. A starting winding 11 on the machine 4 is connected in series with the load circuit and is cut in when the machine 4 is at rest. Excessive speed of the machine 4 is prevented by the provision of a critically self-excited generator on the shaft 5 generating a useful voltage above a predetermined speed which voltage is applied to reduce the current in the load circuit, e.g. by acting on the excitation of the main generator 3. Alternatively, or in addition, any known electrical or mechanical overspeed device may be used. The load motors 1, 2 may be protected against excessive speed by the provision of a critically selfexcited generator on each shaft which energizes an auxiliary exciting winding on the motor at a predetermined speed so as to destroy or reverse the excitation thereof. The response of the exciter 8 may be increased by the provision of a self - excited shunt winding thereon. The exciter 8 may be mounted on the shaft of the generator 3. The protective overspeed dynamo on the flywheel shaft, in addition to acting on the field of the main generator, may act on the field of the flywheel machine so as to avoid transient effects due to differing time constants of the several field systems. A current limiting resister bridged by a normally closed contactor may be inserted in the main circuit upon increase of speed of the shaft 5 above a predetermined value. The series field winding 9 may be shunted by an inductance. In a modification, the excitation of the flywheel machine, in addition to being controlled in accordance with the load current, may be controlled in accordance with the load voltage. In a further modification the flywheel machine may be of the " metadyne " type having two pairs of brushes, one pair of which (the secondary) is connected in the power circuit and the other pair is short-circuited either directly or through a low resistance stator winding thereon, whilst a further constantly excited field winding is also provided, the excitation of which determines the value at which the current in the power circuit will be maintained, A starter field winding is provided on the machine which is arranged to deliver constant current at variable voltage from its secondary brushes. The mean speed of the flywheel machine is prevented from " creeping " by checking it once in each operating cycle of the equipment and acting on the excitation of the main generator or varying the current in the circuit in response to any discrepancy. This may be effected by completing the circuit of a tachometer generator in series with a battery and relay for a time at a predetermined point in each cycle, the relay operating in response to the direction and amount of voltage unbalance to control the generator field. Alternatively, the tachometer generator and relay may be through two reversely connected rectifiers to tapping points on a battery and the relay is arranged to operate in response to the nett ampere seconds passing through it per cycle. The relay may be of the watt-hour meter type operating sliding or camoperated contacts. Specifications 404,739, [Group XXXVII], and 417,517 are referred to.