GB182468A - Improvements in or relating to alternating-current electric motors - Google Patents

Abstract

182,468. Weissberg, E. July 1, 1921, [Convention date]. Alternating-current motors.-Consists in an automatic starting device for single-phase or polyphase motors in which the rotor windings are subdivided into three or more sections, one cf the sections being short-circuited while the other sections are adapted to be successively shortcircuited by means of a centrifugal switch or switches. The winding a, Fig. 1, is permanently short-circuited and the windings b, c are closed in succession as the speed increases by switches e, d carried on centrifugally-operated arms i, h, Fig. 6. To prevent the circuits from opening should an overload cause the speed of the motor to decrease, the levers h, i may be retained in position by an electromagnet g excited by a coil f which is fed from the rotor winding b, c, or mechanical means such as a snapping spring may be provided which only releases the contact members when the speed of the rotor is so reduced that the spring o of the centrifugal switch overcomes the tension of the snapping spring. To reduce the starting-current impulse, a choking coil m, Fig. 5, may be included in the section a which winding may be carried on the centrifugal controller as shown in Fig. 6, or on the shaft l. The choking coil may be of resistance material to increase the " tractional strain." The entire winding a may be of resistance material connected in series with the winding b, both sections being short-circuited by the centrifugal switch e at a certain speed.