An improved apparatus for demonstrating the properties of alternating electric potentials

摘要

473,210. Converting; resistances; educational appliances. BUCKLE, C. May 19, 1936, No. 14190. [Class 38 (ii)] [Also in Groups XV and XXXVI] An arrangement for obtaining alternating potentials from a D.C. source comprises potentiometers 1, 2, 3 fed with D.C. from separate sources 4, 5, 6, the sliding contacts 7, 8, 9 being continuously reciprocated, and the potentials between them and centre tappings on the potentiometers being fed to centre zero voltmeters 10, 11, 12 mounted on a panel 24 on the front of a housing containing the potentiometers and their actuating gear. The latter is driven at low speed by a motor 17 so that slowly alternating voltages, the instantaneous values of which are indicated by the voltmeters, are produced. The apparatus is intended for demonstrating the properties of alternating currents and may include pointers 19, 20, 21 synchronously driven to provide a vectorial representation of the conditions. The driving gear comprises reduction gearing from the motor 17 to a crank-pin 36 which engages three cross-heads 40, 41, 42 coupled to the sliding contacts, or the crank-pin may be coupled to the contacts through connecting rods in which case the resistances may be graduated to compensate for the obliquity of the rods. For three-phase potentials the potentiometers are arranged at 60‹ with the connections of the centre one reversed. The potentiometer 1 may, however, be swung round and clamped by a screw 61 at rightangles to the potentiometer 2 to produce twophase potentials with the potentiometer 3 disconnected. According to the Provisional Specification, the crank and connecting rod mechanism may be replaced by cam and follower mechanism, or the potentiometer resistances may be arranged in a circle to co-operate with rotating sliding contacts.