From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of field circuit characteristics including voltage, resistance, and temperature effects on a dynamo or motor.
Identifier | WestWitteringFiles\E\November1920\ Scan46 | |
Date | 10th November 1920 | |
Contd. -2- EFC1/T10.11.20. additional E.M.F's (cells) to help the current through the field circuit so as to correspond to field circuit resistances less than normal, the idea being that the armature is always loaded just to the extent of the excitation amperes quite apart from the voltage necessary to push these amperes through the field circuit. The curves III and IV of voltage against excitation were taken in these circumstances and, as will be seen, come out with a fairly flat later portion and even a slight droop for the higher values of the excitation. The curves show, as was anticipated, that the loss of P.D. due to the excitation current passing through the armature almost exactly did away with the gain of E.M.F. due to increased flux. It will be noted that in taking these curves, the temperature of the field winding does not matter, as all we are concerned with are the field amperes through the field and armature, and the voltage to overcome field resistance is adjusted accordingly by additional resistance in the one case, or additional E.M.F's in the other. Three inclined lines labelled 4 ohms, 5 ohms and 6 ohms, have been drawn through the origin to represent these values of the resistance of the field circuit corresponding to the three different temperatures. The points of inter-section (a), (b) and (c) with curve III, and (A), (B) and (C) with curve IV, indicate the slight extent in the falling off of the self-excited voltage due to the rise of temperature of the field coils, corresponding to this range of ohms. In most Contd. | ||