GB612357A - Improvements in and relating to apparatus for balancing rotors - Google Patents

Abstract

612,357. Electric indicating systems. BRITISH THOMSON-HOUSTON CO., Ltd. May 20, 1946, No. 15213. Convention date, May 23, 1945. [Class 40 (i)] [Also in Group XX] An indication of the out-of-balance of a rotor, e.g. of a gyroscope, is given by the resultant of two voltages induced in series connected coils due to the vibration of the two ends of a freely-supported stator surrounding the rotor, the coils being connected to a reversing switch. As shown, the rotor is surrounded by a stator (not shown), supported on a spring or springs and having secured at each end thereof a downwardly-extending flexible rod carrying a coil 20, 21, each arranged for movement between a pair of permanent magnets. If the unbalance is on the central vertical axis of the rotor, a simple vertical vibration will'result and the voltages will be equal being 180 degrees out of phase and the resultant zero when switch 26 is thrown right. If there is a pair of equal and symmetrically spaced out-ofbalance points away from the central axis, there will be a tilting tendency, but the voltages will still be equal, the zero resultant however occurring when the switch 26 is left. Generally, both such conditions will occur and the magnitude of each component (but not the position) will be proportional to the voltages with the switch in the two positions, and these voltages are applied in turn to the wattmeter 37 through an attenuator 41, filter 42 and amplifier 43. It is assumed that a voltage so obtained is displaced by an angle # from a voltage A derived from a photo cell 36 receiving light from a lamp 35 deflected by a patch 33 on the rotor, this voltage being converted to one of constant sine wave form by a device 38, and the wattmeter reading will be proportional to A, B, Cos # from which the magnitude of the out-of-balance can be ascertained if a reading is taken with the phase adjuster turned to give maximum wattmeter reading, signifying Cos # equals unity. If the phase.adjuster is then turned until the wattmeter reads zero, the phase angle between the voltages will be 90 degrees, and the angle of turn of the phase shifter to achieve this will give the angle 34 between the patch 33 and the out-of-balance position 32 on a scale previously calibrated by using a known mass in known positions on the rotor. The operation is repeated with the switch 26 thrown the other way to measure the out-of-balance producing a tilting effect as distinct from the purely vertical vibrations. The apparatus may be adapted for an oscillograph instead of a wattmeter.