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1. 发明专利

GB513844A Improvements in or relating to switching apparatus suitable for indicating the magnitude of a transient or abnormal condition in an electric circuit 未知
公开(公告)号：GB513844A
公开(公告)日：1939-10-24
申请号：GB744838
申请日：1939-03-09
申请人： WILLIAM THOMAS JOHN ATKINS , NALDER BROS & THOMPSON LTD , CHMOUL LEIB LIPMAN
IPC分类号： G01R13/00
摘要： 513,844. Electrical measurements. ATKINS, W. T. J., NALDER BROS. & THOMPSON, Ltd., and LIPMAN, C. L. March 9, 1939, No. 7448/38. [Class 37] [Also in Group XXXVII] Apparatus, adapted to indicate the magnitude of an abnormal or transient condition in an electric circuit, comprises means for detecting the condition and a device rendered effective by the detector to initiate the energization of an electrical measuring instrument for a predetermined time, the instrument having means for indicating the maximum deflection thereof. The invention is particularly applicable for indicating abnormal currents in the earth connections of the neutral points of supply networks for fault locating purposes. In one embodiment, a circuit 1 is arranged to carry a current dependent on the condition to be indicated, and, should this current reach a predetermined value, the detector, comprising the moving coil 4 of an instrument having a permanent-magnet or electro-magnetically produced field and energized over a saturated transformer 2 and rectifier-bridge 3, is deflected against the action of a spring 4d to a terminal position where it is held by a spring-catch 7 engaging behind an arm 4b on the spindle 4a thereof. In this position a contact arm 4e on the spindle 4a may close a visual or acoustic signalling circuit and a disc 4f may give a further visual indication of the deflection of the coil 4. A short-circuited coil 5 rotatable in the field of a permanent magnet 5c is mounted coaxially with the spindle 4a, and held in a zero-position by the arm 4b holding back an arm 5b on the spindle 5a of coil 5 against the action of a spring 5d which is weaker than spring 4d. When the coil 4 is deflected as above described the short-circuited coil 5 is released and rotates under the action of spring 5d to a terminal position determined by a stop. During this motion a commutator 8 on the spindle 5a completes the secondary circuit of a transformer 11 for a predetermined time to energize the moving coil 12 of the moving coil measuring instrument 13 through a rectifier-bridge 10. The meter 13 has a frictionally held maximum deflection indicator 14 which thus indicates the maximum current in the circuit 1 during the abnormal condition and cannot again be operated until resetting thereof and of the detector 4. Moving-iron instruments may be used instead of 4, 5 and 12, the rectifiers then being unnecessary. The detector circuit may be controlled by, e.g., a directional relay when it is required to indicate only transient or abnormal currents in a particular direction. In another embodiment, the detector comprises a fuse, which ruptures on occurrence of the condition to be indicated, and releases a switch and a weight, the switch closing the measuring instrument circuit for a time determined by the weight which after a predetermined time closes a switch to short-circuit the instrument.

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