Temperature rise of ventilated railway motor armatures

Abstract

CERTAIN applications, particularly testing, require a sine wave of generator voltage under all load conditions, and the round-rotor type of sine wave generator consequently was developed. The stator is similar to that of a salient-pole machine but for the field a round punched rotor is used with a double layer winding distributed in evenly spaced slots.A comparison of various types of these windings shows that three newly developed connections called the X, U and W types are superior to the old V and Y types, in that 15 per cent or more increase in output can be secured from the rotor without increas ing the maximum coil temperature rise or impairing the voltage wave shape. This change is wrought by eliminating the un desirable features of the old types; namely, too few active coils in the V type, and unequal leg heating in the Y type.The analysis made in this connection is quite general and directly applicable to all round-rotor synchronous machines with double layer rotor coil windings as exemplified by sine wave generators and also synchronous induction motors. By selection of the proper connections any one of the factors desired, wave form, efficiency, and heating, can be stressed to any desired degree. (A.