GB419892A - Improvements in and relating to electrically heated apparatus - Google Patents

Abstract

419,892. Electric hot-plates. RHEINISCH-WESTFALISCHES ELEKTRIZITATSWERK AKT.-GES., 38, Mõrkischestrasse, Essen, Germany. July 19, 1933, No. 20424. Convention date, March 8. [Class 39 (iii).] In electrically-heated apparatus such as hot-plates, the heating resistance is connected to the mains in such a manner that a current flows in the element higher than the maximum current which can flow when the apparatus is connected to its nominal voltage, the resistance being automatically disconnected after a limited period of time before it is damaged. For example two elements a and b, provided with a series parallel switch c and normally connected between an outer conductor R and the neutral O of a polyphase system, may be connected by a switch e across the two outer conductors R and S to give an overload current in the element. The thermostat d opens switch e when the temperature of the apparatus reaches a certain limit. The switch e may be replaced by a switch f. When this switch makes the connections shown by the continuous lines both elements are connected in parallel between the two outers R and S. When the thermostat acts the connections shown by the dotted lines are made and the apparatus is thereby connected up in the manner determined by switch c which has already been set. The thermostat d may be connected to the hot plate, by a heat conducting connection as shown in Fig. 12. If only one voltage can be obtained from the mains a transformer i may be provided to give the overload voltage, disconnecting thermostats d<1> and d<2> being provided. The overload may also be obtained simply by the use of the highest step in series parallel regulation.