GB495893A - Improvements in or relating to the starting of direct current motors - Google Patents

Abstract

495,893. Control of D.C. motors. CANTIERI RIUNITI DELL ADRIATICO, CANTIERE MONFALCONE. June 26, 1937, No. 17848. Convention date, June 27, 1936. [Class 38 (iii)] Varying E.M.F.-To facilitate the starting of a D.C. motor M and its supply finally from a main D.C. generator Dp, an auxiliary generator Da also supplies current in opposition to the main generator and is gradually cut out as the motor speeds up, the auxiliary generator being then available for starting another motor. The two generators may be mounted on the same driving shaft and they are arranged during starting in series opposition so as to supply current to the motor through the upper contacts of switch Co. The arm of the rheostat Ra is then in its lowest or inoperative position, so that the field e of the auxiliary generator Da is fully excited. As the motor speeds up, the arm of the rheostat is raised slowly, thus gradually reducing the voltage of generator Da, the arm being then held in its raised position by electromagnet F. When the speed of motor M is high enough switch Co is operated to open its upper and close its lower contacts, thus cutting generator Da out, when electromagnet F is de-energized and rheostat arm Ra falls, cutting out the rheostat ready for starting another motor connected to the mains. The rheostat may be dispensed with and an opposed field winding for the generator Da may be connected across the motor M so that the generator Da is automatically cut out as the motor speeds up.