GB554349A - Improvements in dynamometer excitation control systems - Google Patents

Abstract

554,349. Exciting dynamo-electric machines. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). Feb. 20, 1942, No. 2269. [Class 35] [Also in Group XIX] A dynamometer 14 of eddy current swinging carcase type, is excited so that its torque-speed curve can be matched to that of the load which will be driven by the engine 12 to be tested. Dynamometer field coil 20 is supplied by the armature 17 of an exciter 19 driven by the engine shaft 13, or at a proportionate speed. Its field coil 25 is supplied, in series, by a constant potential from divider 26 across source 24, and by the armature 16 of a second exciter 18 running at the same or a proportionate speed and excited by constant source 24. The exciters 18, 19 are worked in the unsaturated condition so that their output is proportional to their speed. As a result the dynamometer excitation-speed curve has both linear and quadratic components ; when switch 21 is put in the middle position potential divider 21a across source 24 adds a constant component to the output from armature 17. When switch 21 is in the right-hand position only a constant component is left. The various components can be adjusted by resistances 30, 27, 22 and 23, and by switch 31 the quadratic component can be eliminated. In a modification, (i) an amplifier, such as a motor-generator set with a generator of the cross-field type described in Specification 539,835, or an electronic amplifier, is interposed between armature 17 and coil 20, (ii) the potential divider 26 and armature 16 supply separate field coils in exciter 19, (iii) a potential divider across source 24 supplies a constant excitation to a separate field coil in the dynamometer. Any power law between the first and second can be approximated to, by adjusting the three components of the excitation. If the exciters are small, as when an amplifier is used, they need not be cradled with the dynamometer.