Patent GB-756144-A (GB)
Title: Improvements in or relating to calculators
Inventor: BAILEY DESMOND
IPC: G06G1/00
Filed: 1952-05-02
Abstract: 756,144. Calculating-apparatus. STANDARD TELEPHONES & CABLES, Ltd. Jan. 2, 1953 [May 2, 1952], No. 11146/52. Class 106 (1). [Also in Group XVIII] Calculating-apparatus, for determining the saving effected by increasing the power factor of an electrical installation from one value to another and the reactive correction required to effect such a saving, comprises slides or moving panels bearing, or moving along, curves representing the relevant functions. In one embodiment, a slide 16 is guided by washers on studs 14 between two plates and bears a scale 20 which co-operates with a curve 22 marked on a slide 17 movable at right angles to the slide 16. The curve represents the function 1/P - 1 plotted in accordance with the scale 20 against the power factor P for which a scale 21 is marked along the edge of the aperture in the face plate through which the curve is visible. With the slide 17 in the position shown and the slide 16 set according to the existing power factor P E , the intercept on the scale 20 represents the saving in KVA. per KW. obtainable by making the power factor 1. If the power factor is to be increased to a value Pa, less than one, the slide 17 is first moved until the intercept of the curve on the scale 21 represents the power factor to be achieved. To facilitate this setting, an index 26 on the slide 17 co-operates with a scale 24 marked along the upper edge of the aperture. The intercept on the scale 20 is then equal to 1/P E  - 1/P R  which represents the saving obtained. A further slide 18 moving parallel to and beneath the slide 17 bears a curve 23 representing the function (1/P<SP>2</SP>-1)<SP>¢</SP>. The intercept of this curve along the scale 20 represents the capacity in KVAr per KW required to increase the power factor by the desired amount. This slide bears an index 27 for co-operation with a scale 25 to enable the slide to be set in accordance with a required power factor. The areas on the slides 17, 18 beneath the curves are differently coloured. The face and base plates have notches 13 to facilitate manipulation of the slides which have projections 19 to prevent their withdrawal. In another arrangement, differently coloured panels 3, 4 are guided by runners 5 engaged in grooves 7 to move in a curve representing the variation of 1/P with P. The panels are visible through an aperture provided with a power factor scale and a scale indicating the KVA. demanded for a 100-KW. load. The panels 4, 3 are set respectively according to the existing and required power factors, the saving to be obtained being shown by the thickness of the panel 4 appearing to the right of the panel 3. Figures representing the saving and the capacity required to effect the desired increase in the power factor may be marked on the panel 4 so as to appear through perpendicular slots in the panel 3 and face plate when the panels 3, 4 are in certain predetermined positions. The apparatus may be large for display purposes in which case the slides may be repeatedly driven through a predetermined cycle of operations. The display apparatus may be associated with a demonstration circuit in which a correcting capacity is inserted.