Improvements in Alternate Current Measuring and Indicating Instruments.

摘要

22,330. Mordey, W. M. Dec. 7. Current and energy meters.-An alternating- current electrodynamometer contains a horizontally-pivoted loop f of a metal having a low temperature-resistance coefficient, forming a closed electric circuit of low resistance, provided with a pointer g, and controlled by a spring or a weight. Part of the loop is situated within the iron circuit c of a stationary transformer, having a fixed pressure coil b, by which a large secondary current is induced in the loop f. This coil b may be of copper wire. Another part of the loop surrounds a stationary coil a, carrying the main current, which causes deflection of the loop. The pointer moves over a suitably-graduated scale on which deflections are read ; or the loop may be connected by a spring to a torsion head, the rotation of which is observed, necessary to return the loop to its zero position, as in a Siemens' dynamometer. The loop f may consist of more than one turn of wire. The instrument may be used as a voltmeter or ampere meter, both stationary coils a, b being connected in one circuit, or the deflecting- coil a supplied with current from a secondary fixed on the transformer c. Such instruments are stated to be accurate on circuits having low power factors, and to be independent of frequency variations.