GB293705A - A device for protecting transformers, switches, motors, generators, and similar electrical machines and apparatus - Google Patents

Abstract

293,705. Buchholz, M. July 8, 1927, [Convention date]. Transformers. -- The evolution of gases of decomposition &c., for example from transformers or switches when conditions are abnormal, causes the operation of indicating or cut-out devices. For this purpose the gases are led past an electrically heated device so as to cause a change in the rate at which heat is conducted away from the device and therefore a change in the temperature of the device.. According to the arrangement of Fig. 1, when gases ascend from a transformer tank through a tube a, the change in thermal conductivity of the medium surrounding a current-carrying resistance wire or strip c causes a change of temperature of and change of resistance of the wire. This causes a deflection of the needle e<1> of a registering instrument d, and the needle may engage a contact e<2> and operate a signalling or cut-off device. The gases may also operate directly a second contact device f. In a modification, Fig. 2, the wire c lies in a tube containing ether or the like, the expansion of which operates a contact device. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a construction, Fig. 3, in which the heat of the gases causes a wire h to sag and operate a contact device. The wire h is connected to a device i in a casing k to compensate for fluctuations of normal temperature. A modification of the Fig. 1 device is also described in which a second wire c is arranged in a Wheatstone Bridge circuit with the first wire c to compensate for fluctuations of normal temperature. This subject-matter does not appear in the Specification as accepted. Specification 241,228 is referred to.