GB578859A - Improvements in or relating to power indicating or measuring devices - Google Patents

Abstract

578,859. Electric indicating systems. SHEPHERD, G. R. (Westinghouse Electric International Co.). April 13, 1944, No. 6852. [Class 40 (i)] [Also in Groups XIX and XXXVI] A device for indicating or measuring the power output of a rotating shaft is characterized by a single magnetic flux producing electromagnetic unit comprising a stationary member having an electrical coil and a member rotatable with the shaft and responsive to the toraue and speed characteristics of the shaft for inducing a voltage in the coil indicative of the power of the shaft. The rotatable member comprises two axially displaced torque rings 7 and 9, Fig. 1, mounted on shaft 1 by means of non-magnetic bushes 13 and a central toothed member 17 also mounted on shaft 1 by means of a non-magnetic bush 19. The torque rings 7 and 9 each have axially extending fingers 7a and' 9a which are so positioned as to form the air gaps 6 and 8, Fig. 2, with the teeth 15 of the member 17. The stationary member 5 is of magnetic material and forms air gaps 24 and 26 with the torque rings 7 and 9. The member 5 has teeth portions 27 having windings 29 in series or in parallel and attached to an indicating instrument 31. Either the member 9 or the member 5 is a permanent magnet producing a flux flowing in the path shown, i.e., member 5, gap 26, member 7, finger 7a, air-gap 6, a tooth 15, air-gap 8, finger 9a, member 9, air-gap 24, member 5. When the shaft 1 is stationary or rotating at no load the flux path is unaltered but when the shaft is rotating at load circumferential distortion due to the transmission of torque takes place, the air gaps 6 and 8 are altered and a magnetizing force appears across the air-gaps 28 between the teeth 15 and the tooth portions 27 causing a flux to flow in the said tooth portions 27 thus generating a voltage in the winding 29 which is proportional to the speed of the shaft and to the torque transmitted, i.e., is a measurement of the power transmitted. In another embodiment not shown coils are used to obtain the magnetic induction instead of a permanent magnet. The faces of the teeth 15 and of the fingers 7a and 9a are shaped and dimensioned to compensate for relative changes of position of the component parts due to changes of temperature, end thrust of the shaft, and/or bending of the shaft.