GB595418A - Improvements in or relating to systems for continuously measuring the power output of a rotating shaft - Google Patents

Abstract

595,418. Dynamometers. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. Jan. 26, 1945, No. 2132. Convention date, Nov. 19, 1942. [Class 106 (ii)] , [Also in Group XXXVIII] A system for continuously measuring the power output of a rotating shaft comprises a rotor assembly secured to rotate with the shaft, a stationary member disposed in close proximity to the rotor assembly, electrical coil means associated with said stationary member, means for producing a potential varying in magnitude with the speed of rotation of the shaft for energizing said electrical coil means which arc in flux linkage with said stationary member and said rotor assembly upon energization thereof, means included in the rotor assembly for changing the value of the flux linkage by an amount corresponding to the torque of said shaft thereby changing the value of a voltage in said electrical coil means, and means for measuring the voltage in said coil means, whereby the power output of said shaft is indicatecl. A rotor assembly 3 comprises a pair of axially spaced torque rings 7 and 9 and a reference ring 11 secured on non-magnetic bushings to a shaft 1, the power output of which is to be measured. Each of the torque rings 7 and 9 has a plurality of axially extending fingers 15, 17 which are of sufficient length to overlap the extremities of axial fingers 13 on the reference ring 11 forming small air gaps 19 and 21 as shown. When the shaft 1 is transmitting torque the size of the air gaps 19 9 and 21 will change due to torsional deflection of the shaft, the air gaps- 19 increasing and the air gaps 21 decreasing or vice versa depending on the direction of twist of the shaft. The rotor assembly 3 co-operates with a stator member 5 comprising an outer annular shell 23 having secured therewithin axially spaced ring elements 25, 27, 29 positioned to form air gaps 31, 33 and 35 respectively with the rotor assembly 3. A pair of annular coils 37 and 39 'are positioned within said ring elements 25, 27, 29 as shown and are energized with a voltage produced by a generator 45 which is driven by the shaft in any convenient manner. An inverter 44 converts the D.C. voltage of generator 45 to A.C. to energize the coils 37 and 39, which are each connected as one leg in a conventional bridge circuit which is balanced for the condition of no load on the shaft 1, and creates a flux across the air gaps 31, 33, 35 and 19, 21. When the shaft 1 is transmitting a load the voltage in the coils 37, 39, which is proportional to the speed of the shaft 1 since the generator 45 is driven by the shaft, is varied by reason of the change in the air gaps 19 and 21, previously explained, causing the flux in the path round the coils (see Figure) to be changed to vary the voltage in the coils proportionally to the speed and torque. This change in voltage is measured so giving a measure of the power output of the shaft.