GB696152A - Improvements in electric dynamometers - Google Patents

Abstract

696,152. Systems depending on two or more machines. HEENAN & FROUDE, Ltd. Feb. 12,1952 [Feb. 13, 1951], No. 3428/51. Class 38 (iv). In plant for running-in and subsequently testing a prime-mover 1, comprising a D.C. dynamo-electric machine 2 coupled to the prime mover and electrically connected to another machine 4 coupled to an A.C. machine 3A which receives power from or supplies power to an A.C. source 8, according as to whether the prime-mover is being driven by or is driving the machine 2, the power which can be supplied to the source 8 during testing is limited by an eddy current brake or dynamometer 5 arranged either on the same shaft as the prime-mover or, as shown, on the shaft common to the machines 3A, 4. Variable excitation for the brake is supplied by a unit 6 automatically controlled by a device 7 responsive to the magnitude and direction of current flow between the machines 2, 4, the arrangement being such that excitation is progressively increased with increasing current flow from machine 2 to machine 4. Device 7 may comprise an elementary inductor alternator having a toothed rotor which is driven at constant speed past a single pole carrying (1) an A.C. output winding, (2) a control winding through which passes the current of machine 2, and (3) a biasing winding, adjustably excited by D.C., for controlling the power output level at which excitation of the brake commences. The A.C. output of device 7 is applied, after valve amplification, to the control grids of controlled rectifiers forming part of the unit 6 and thus control the brake excitation by control of the firing-point of the rectifiers. When the generated power is used to supply a works load which is also partly supplied from the source 8, device 7 may have a further winding carrying D.C. proportional to the load current supplied by source 8, so that the effects of sudden changes in the magnitude of the work load are counteracted by the brake. The machine 2 and brake 5 may be mounted on trunnions for torque measuring purposes. Specification 229,427, [Class 106 (ii)], is referred to.