[LB014214], Letter from Thomas Alva Edison to Spencer Borden, October 4th, 1882



Please accept thanks for letters of S. B. Paine referred to me and which are returned herewith.##I think that upon investigation you will find that the Maxim people [use an extra coil] either around their field magnet or around their [--cites] This extra coil being in the line and as lamps are added it strengthens the field so as to compensate for the drop of Electro-motive force in the armature. They are comp[ared] on account of the great drop within the armature due to [load] and small mass of iron, to use a separate [----] otherwise a few lamps would make a great difference, while the drop in our armature due to load is comparatively small, but too large where there is great resistance in consumption.##The trouble with the Maxim devices is that it does not regulate for speed but only for more or less lamps, and a variation of speed causes a greater variation in candle power than it would if the device was not used. Another defect is the use of an [----] which if it should break down, would stop one or all the main line dynamos.##Where you get an order with regular speed but variable load we can send you a hollow bobbin to slip over your fields which will regulate for load but not for speed- of course like Maxim's device there will be a loss of energy on this device.##about thirty different kinds of Automatic regulators have been made and tested at Menlo Park, some that regulate for speed only, some for lamps only, and some regulate lamps and make their candle power constant, independent of the number or speed. Out of all these I have selected one which I think can be made satisfactory in the hands of the public, so far it has worked perfectly. It will be just the thing for irregular power. I will be able to supply them in about six or eight weeks. They go inside the regulator resistance box and have no perceptible loss of energy. Please investigate the Maxim device and report if my answers are correct as to not regulating for both speed and lamps.









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[LB014214], Letter from Thomas Alva Edison to Spencer Borden, October 4th, 1882

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Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University

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