Patent GB-991292-A (GB)
Title: Improvements in or relating to arrangements for determining the conditions for maximum efficiency of operation of direct current generators
IPC: H01L21/00
Filed: 1962-11-23
Abstract: 991, 292. Determining maximum operating efficiency of D.C. generators. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Nov. 23, 1962 [Nov. 27, 1961], No 44385/62. Heading G1U. [Also in Division H1] In an arrangement for determining the point on the operating characteristic of a direct current generator G corresponding to maximum operating efficiency, there is included a resistance measuring bridge fed on one of its diagonals by an alter - nating current source P in which the generator G and a variable resistor R constituting its load resistance constitute a pair of first series arms of the bridge, while the two other arms of the bridge R<SP>1</SP>, R<SP>11</SP> are related in such a way that when the bridge is balanced the maximum efficiency of the generator is achieved. A servo mechanism A, D, M is coupled to the output diagonal of the bridge so as to control the variable resistor in a manner such that the bridge is made to balance. For maximum efficiency the internal resistance of the generator G equals its load impedance, which is R if the impedance of the A.C. source is negligible, so that in these conditions the bridge must be set up with R<SP>1</SP> = R<SP>11</SP>. If the impedance of the A.C. source is not negligible then it must be arranged that one of the resistors R<SP>1</SP>, R<SP>11</SP> is also controlled by the servo mechanism, so that the bridge balance condition is established when G = R + R s  where R s  is the source resistance, i.e. when the ratio R<SP>11</SP>/R<SP>1</SP> = 1 + Rs/R. To operate the servo the output from the bridge is fed via an amplifier A to a synchronous demodulator D also supplied from the source P with a signal of the same phase as the original input and thence to a motor M which is coupled so as.to drive the variable resistor R. To determine the operating conditions for maximum efficienty instruments I and V are included to measure the operating D.C. current and voltage of the generator at maximum efficiency. Two applications of the system of the invention are described. One (Fig. 5) refers to the grading of photo-cells during their production. The manufactured photo-cell C is connected into the apparatus of the invention PM and subjected to a uniform illumination L. The apparatus adjusts conditions so that the photo-cell is functioning with maximum efficiency. The measuring apparatus I and V are connected so as to control two servo mechanisms S I  and S V  respectively, which are arranged to drive motors M I , M V  so as to adjust a drawer T to a position dependent on both of the readings. When the photo-cell is released from the measuring apparatus it falls into its appropriate section in the drawer. A second application (Fig. 6) refers to the control of the manufacture of a photo-cell. By preliminary experiments the operating current at maximum efficiency of photo-cells in a batch having optimum maximum efficiency is determined. The photo-cells whose manufacture is under control are then set up in an etching bath CD and connected into the arrangement PM of the invention. The operating conditions are continuously adjusted for maximum efficiency throughout the etching process and when the instrument I indicates the current at which the optimum maximum efficiency is obtained a relay is actuated and the servomechanism SI operated so as to control the motor M. This actuates a mechanism E n  which lifts the photo-cell from the bath CD and immerses it in a water bath CN so as to stop the etching process. Specification 991,291 is referred to.