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Title: |
1892 Image-Thomson-Houston Electric Co., 1879 Dynamo |
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Source: |
Electricity, 27 Jul 1892 pg 17 |
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Insert Date: |
10/9/2011 5:37:04 PM |
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This machine, which varies only in detail from those manufactured by the Thomson-Houston Company to-day, embodied the famous three-coil armature, and is too well-known to need more than a passing word of description. The design of the machine was entirely original and unique, being different from any dynamo built before or since. The field magnets, as will be seen from the illustration, consist of four cylindrical cores expanded at one end and enclosing the armature. Upon these cylinders the field coils are wound, and the two parts of the frame are held in position by heavy bolts through the outer yokes, forming part of the magnetic circuit. The armature contains but three coils, the axes of which lie at an angle of 120° from each other. In order to balance the length of the coils, half of each coil is wound on the Core beginning with number one, then number two and number three; and then the second half of each is continued, but in inverse order of the numbers. This arrangement equalizes the resistance of the coils and their average distance from the armature core. The three inner ends of the coils are connected together, and the outer ends are brought to a commutator of three segments. The field magnets and armature bearings are supported on a framework resting upon the floor. The armature of this machine was wound with a double wire, and had about 60 pounds of copper on it. The field magnets each had about 50 or 60 pounds, making the total weight of the copper in the machine about 275 pounds. The position of the two sets of brushes on the commutator is such that the continuity of the circnit is not, broken. The first machines were of such moderate capacity as not to need any particular means for preventing the flashing at the commutator, a difficulty which developed later with the larger capacity machines. This difficulty, was, however successfully met by Prof. Thomson in his invention of the air blast mechanism applied to the commutator for preserving the insulation. To avoid flashing when a brush leaves a segment, a blast of air is directed on the commutator at every one-third of a revolution. The armature was wound by Prof. Thomson, assisted by Mr. Thomas McCollin, and the field also. The whole shop work upon the machine was done at the Harrison Machine Shop, 18th and Barker Sta., Philadelphia. The machine was completed early in March, 1879. It originally ran 4 arc lamps, each taking 20 amperes, the wires on the armature and field in this case being connected in multiple. When the wiring was in complete series, the dynamo ran 8 arc lamps, each taking 10 amperes. The machine was installed in the bakery located on 18th St., Philadelphia. It is the first machine having a 3-segment commutator and the connections of a 3-coil machine complete. The brushes and brush-holders are not on the machine, as shown by the photograph, neither are the binding posts. The total weight was perhaps something like 1.100 or 1,200 pounds. This dynamo was the object of much expert criticism, and numerous predictions of its impracticability were heard, but notwithstanding all this, the Thomson-Houston arc light machines probably operate more lamps than all the other classes of arc light dynamos put together. |
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