GB474193A - Improvements in or relating to single-phase electric motors - Google Patents

Abstract

474,193. Alternating current commutator motors. STALDER, M. Jan. 22, 1937, No. 2018. Convention date, Jan. 23, 1936. [Class 35] In a motor of the type which runs as a repulsion-motor up to a certain speed, the rotor being then short-circuited so that it runs as an induction-motor, the brushes and brush-lifting gear are replaced by mercuryswitching arrangements. For this purpose a number of hollow cylindrical bodies are arranged on the rotor shaft and each such body is provided with such a number of equally spaced contacts that the angle between two connecting contacts on the same cylindrical body is equal to the brush angle of an ordinary motor. The Figure shows an arrangement for a four-pole machine with twenty-eight rotor bars, so that there are seven hollow bodies and each one has four of the contacts K<1>, K<8> .. .... K<16> ; two consecutive contacts K<1>, K<8> on one of the bodies being 90‹ apart. The angle between a contact K<8> on one of the bodies and the consecutive contact K<9> on the next body is <1>/28 of the circumference. Each of the hollow bodies contains a quantiy of mercury sufficient to short-circuit two of the contacts when the mercury is collected at the bottom of the body, but when the machine attains a certain speed the mercury is distributed round the circumference of the cylinder and all the contacts are short circuited. The effect of shifting the brushes in an ordinary motor can be obtained by displacing the switching arrangement angularly with respect to the rotor.