Dynamoelectric machine and method for manufacturing same

A rotor for a dynamoelectric machine having a stator assembly including a stator core having slots therein and energizable windings on the stator core, the rotor comprising a stack of generally thin, circular rotor laminations made of highly magnetically permeable material, each rotor lamination having slots therein spaced circumferentially around its periphery and each slot including a radially inner portion and a radially outer skew portion extending outwardly and laterally from the radially inner portion toward the circumference of the rotor lamination, each slot overlapping corresponding slots on the other rotor laminations in the stack such that the overlapping slots of the rotor laminations define passages extending axially through the rotor, and electrically conductive material disposed in each of the passages, the rotor laminations in the stack being arranged in at least two sets, the slots of a first of said sets of rotor laminations having their skew portions extending laterally in a first direction and the slots of a second of said sets of rotor laminations having their skew portions extending laterally in a second direction opposite the first direction, the radially inner portions of corresponding slots in said first and second sets of rotor laminations generally overlying each other, the laterally outermost points of the skew portions of the corresponding slots in said first set of rotor laminations lying generally along a first axially extending line and the laterally outermost points of said skew portions of the corresponding slots in said second set of rotor laminations lying generally along a second axially extending line, the distance d between the first line and second line falling within a range expressed by the following equation,

• (2.pi.r)/(2S-P)<d.ltoreq.(2.pi.r)/(2S-P)+.delta.+.rho.
• where r is the distance between the center of a rotor lamination and the laterally outermost point of the skew portions of one of the slots on the rotor lamination, S is the number of slots in the stator core, P is the number of poles of a selected one of the windings, .delta./2 is an amount selected to inhibit the occurrence of more than one saturation region associated with each rotor slot, and .rho./2 is approximately the distance between first and second parallel planes, the first plane including the radially outermost point of the slot and the second plane including the first or second axially extending line nearest the radially outermost point, the first and second planes being perpendicular to and intersecting a third plane including the first and second lines.

A method of assembling a dynamoelectric machine comprising the steps of:

• providing a stator assembly including a stator core having slots and a bore therein, energizable windings disposed on the stator core, and at least one bearing;
• providing a rotor assembly comprising a shaft supported by the at least one bearing, and a squirrel cage rotor fixedly mounted on the shaft for conjoint rotation therewith, the rotor being disposed at least in part in the stator core bore, and the rotor and stator assembly being adapted for magnetic coupling therebetween during energization of the windings;
• stacking generally thin, circular rotor laminations made of highly magnetically permeable material to form the rotor, each rotor lamination having slots therein spaced circumferentially around its periphery and each slot including a radially inner portion and a radially outer skew portion extending outwardly and laterally from the radially inner portion toward the circumference of the rotor lamination, each slot at least partially overlying corresponding slots on the other rotor laminations of the stack such that the at least partially overlying slots of the rotor laminations define passages extending axially through the rotor, and electrically conductive material disposed in each of the passages;
• arranging the rotor laminations in the stack in at least two sets, the slots of a first of said sets of rotor laminations having their skew portions extending laterally in a first direction and the slots of a second of said sets of rotor laminations having their skew portions extending laterally in a second direction opposite the first direction, the radially inner portions of corresponding slots in said first and second sets of rotor laminations overlapping each other;
• said step of arranging further including the step of positioning the laterally outermost points of the skew portions of the corresponding slots in said first set of rotor laminations generally along a first axially extending line and positioning the laterally outermost points of said skew portions of the corresponding slots in said second set of rotor laminations generally along a second axially extending line, the distance d between the first line and second line falling within a range expressed by the following equation,
• (2.pi.r)/(2S-P)<d.ltoreq.(2.pi.r)/(2S-P)+.delta.+.rho.
• where r is the distance between the center of a rotor lamination and the laterally outermost point of the skew portions of one of the slots on the rotor lamination, S is the number of slots in the stator core, P is the number of poles of a selected one of the windings, .delta./2 is an amount selected to inhibit the occurrence of more than one saturation region associated with each rotor slot, and .rho./2 is approximately the distance between first and second parallel planes, the first plane including the radially outermost point of the slot and the second plane including the first or second axially extending line nearest the radially outermost point, the first and second planes being perpendicular to and intersecting a third plane including the first and second lines.