GB267612A - Improvements in and relating to current generating and controlling appliances particularly applicable for use in electric arc welding - Google Patents

Abstract

267,612. Quasi-Arc Co., Ltd., and Strohmenger, A. P. Dec. 18, 1925. Supplying and controlling consuming devices. -An electric generator for arc welding has a shunt field winding and a series field winding tending to oppose strong fluctuations of current and the magnetic circuit is formed so that there are at least two zones located at different axial positions along the armature, one of which is saturated even at low armature voltages while another remains unsaturated practically throughout the whole working range. Fig. 1 shows diagrammatically a generator 1 having a shunt field winding 2 and rheostat 15, a back-compounding winding 3, and an interpole winding 6. The armature, Fig. 3, is stepped axially so as to provide a central unsaturated zone having a long airgap 18 and two saturated zones at the ends having short air gaps 21. This is effected by disposing the winding in slots which are open in the middle part while the teeth 19 project at the ends. Alternatively, the pole faces may be stepped. The series field windings 3 which are disposed near the ends of the poles so as to localize flux changes in the air-gap zone, are given a high self-induction by embedding them in slots, or the conductors themselves may be in iron. The shunt field winding is made with heavier wire and fewer turns than usual so as to reduce the time of building up the field, and the field poles are normally fairly saturated. To compensate for fluctuations, in the load circuit, a reactance is provided comprising cores 7, 10 carrying a primary winding 9 in series with the load and a secondary winding 11 in the shunt field circuit. These windings set up opposed fluxes. The limb 10 is preferably of cast iron so as normally to be highly saturated. The primary winding 9 is given a high self inductance by embedding it in the laminated core 7 or by constructing it of iron wire. With this arrangement, the reactance of the winding 9 is high when the load current is small, but with a heavier current, the effects of windings 9 and 11 more nearly counterbalance and the reactance is reduced. Tappings may be taken from the winding 9 and connected to a series parallel switch, and one or more air-gaps 8 which may be variable are formed in the core 7,