Rotor resistor assembly for ac induction motors

Claim 2

A rotor resistor assembly for an electric motor including a stator, a rotor including a shaft, and a winding carried by said shaft and rotatable relative to said stator, said rotor resistor assembly comprising: a support member including a hub mounted on said shaft terminating in axially spaced radial end portions; a plurality of coiled bar resistors, said coiled bar resistors formed by metal bars having a predetermined resistance and forming coils having a plurality of spaced substantially circular coil turns extending circumferentially around said hub and progressing axially between said radial end portions; a plurality of movable mounting assemblies supported for movement relative to said radial end portions of said support member; plural bracket means extending axially from said movable mounting assemblies for connecting said plurality of movable mounting assemblies to said substantially circular coil turns of said coiled bar resistors at equally circumferentially spaced locations, whereby said coil turns of said coiled bar resistors are mounted in a balanced relationship to said support member for preventing lateral movement with limited radially inward and outward movement being provided relative to said support member in response to variations in thermal expansion and to centrifugal forces developed on said coil bar resistors when said shaft is rotated at high speeds; and conductor means electrically connecting said coiled bar resistors to said windings of said rotor.

Claim 3

A rotor resistor assembly for an electric motor including a stator, a rotor including a shaft, and a winding carried by said shaft and rotatable relative to said stator, said rotor resistor assembly comprising: a support member including a hub mounted on said shaft terminating in axially spaced radial end portions; a plurality of coiled bar resistors formed by metal bars having a predetermined resistance and wound in coils extending circumferentially around said hub and forming plural coil turns progressing axially between said radial end portions; a plurality of pivotal linkages including first and second ends and middle portions intermediate said first and second ends; means connecting said first ends of said plurality of pivotal linkages to said plurality of coiled bar resistors; means pivotally connecting said middle portions of said plurality of pivotal linkages on equally circumferentially spaced lOcations of said radial end portions of said support member so that said pivotal linkages are movably mounted relative to said support member in a rotationally balanced relationship whereby said coiled bar resistors are movable radially inward and outward relative to said support member in response to variations in thermal expansion and to centrifugal forces developed when said shaft is rotated at high speeds; a counterweight means connected to said second ends of said plurality of pivotal linkages for applying radial inward forces to said coiled bar resistors to restrain the radially outward movement of said coils when said shaft is rotated at high speeds; and conductor means for connecting said coiled bar resistors to said winding of said rotor.

Claim 4

A rotor resistor assembly for an electric motor including a stator, a rotor including a shaft, and a winding carried by said shaft and rotatable relative to said stator, said rotor resistor assembly comprising: a support member including a hub mounted on said shaft terminating in axially spaced radial end portions; a plurality of coiled bar resistors formed by metal bars having a predetermined resistance and wound in coils extending circumferentially around said hub and forming plural coil turns progressing axially between said radial end portions; a plurality of pivotal linkages including first and second ends and middle portions intermediate said first and second ends; means connecting said first ends of said plurality of pivotal linkages to said plurality of coiled bar resistors; means pivotally connecting said middle portions of said plurality of pivotal linkages on equally circumferentially spaced lOcations of said radial end portions of said support member so that said pivotal linkages are movably mounted relative to said support member in a rotationally balanced relationship whereby said coiled bar resistors are movable radially inward and outward relative to said support member in response to variations in thermal expansion and to centrifugal forces developed when said shaft is rotated at high speeds; a counterweight means connected to said second ends of said plurality of pivotal linkages for applying radial inward forces to said coiled bar resistors to restrain the radially outward movement of said coils when said shaft is rotated at high speeds; and conductor means for connecting said coiled bar resistors to said winding of said rotor.

Claim 5

A rotor resistor assembly for a dynamoelectric machine having a stator and a rotor including a shaft carrying a polyphase winding having plural phase windings rotatable relative to said stator, said rotor resistor assembly comprising: a support member mounted on said shaft including a hub terminating in radial end portions; a plurality of substantially identical resistors including one resistor for each of said plural phase windings wherein said resistors are formed by metal bars having substantially identical lengths and predetermined resistances, each of said metal bars being formed in a coil forming a plurality of substantially circular coil turns terminating in first and second coil ends, said coil turns being circumferentially disposed about said hub and wound progressively in an axial direction extending between said radial end portions of said support member with the sides of said coil turns being mutually spaced apart a predetermined axial distance for providing heat radiating surfaces exposed to air circulated therebetween; said first coil ends of each coil being equally circumferentially spaced relative to said first coil ends of the other coils and said second coil ends of each coil being equally circumferentially spaced relative to said second coil ends of the other coils; means fixedly mounting said first coil ends and said second coil ends on said support member so as to maintain said circumferentially spaced relationship of said first and said second coil ends, whereby said resistors are symmetrically mounted to maintain rotational balance of said rotor resistor assembly and are expandable between said first and second coil ends; and electrical conductor means electrically connecting said first coil ends and said second coil ends in a circuit including each of said phase windings of said rotor.

Claim 6

A rotor resistor assembly for a dynamoelectric machine having a stator and a rotor including a shaft carrying a polyphase winding having plural phase windings rotatable relative to said stator, said rotor resistor assembly comprising: a support member mounted on said shaft including a hub terminating in radial end portions; a plurality of substantially identical resistors including one resistor for each of said plural phase windings wherein said resistors are formed by metal bars having substantially identical lengths and predetermined resistances, each of said metal bars being formed in a coil forming a plurality of substantially circular coil turns terminating in first and second coil ends, said coil turns being circumferentially disposed about said hub and wound progressively in an axial direction extending between said radial end portions of said support member with the sides of said coil turns being mutually spaced apart a predetermined axial distance for providing heat radiating surfaces exposed to air circulated therebetween; said first coil ends of each coil being equally circumferentially spaced relative to said first coil ends of the other coils and said second coil ends of each coil being equally circumferentially spaced relative to said second coil ends of the other coils; means fixedly mounting said first coil ends and said second coil ends on said support member so as to maintain said circumferentially spaced relationship of said first and said second coil ends, whereby said resistors are symmetrically mounted to maintain rotational balance of said rotor resistor assembly and are expandable between said first and second coil ends; and electrical conductor means electrically connecting said first coil ends and said second coil ends in a circuit including each of said phase windings of said rotor.

Claim 7

In a wound rotor induction motor, the combination comprising: a frame; a stator carried on said frame; a shaft rotatably supported by said frame and including a shaft extension extending externally of said stator; a rotor secured to said shaft including polyphase windings mounted for rotation adjacent said stator; a support member including a hub mounted on said shaft extension and a fan impeller means extending radially of said hub, said support member further including a pair of end portions extending radially from the ends of said hub, one end portion of said pair of end portions including a plurality of terminal connections insulated from each other and from said one end portion and the other end portion of said pair of end portions being formed of an electrically conductive material and including terminal connections being electrically interconnected by said electrically conductive material; a resistor assembly including plural resistors made of a stainless steel bar material and formed in axially aligned coils formed by coil turns wound circumferentially around said hub and progressing axially in mutually spaced relationship between said pair of end portions of said support member, each of said coils including first and second coil ends which are axially spaced relative to each other and to said pair of end portions of said support member; a plurality of movable mounting assemblies supported for movement relaTive said support member including insulatingly interconnected and spaced-apart stirrup brackets connected to each of said coil turns forming said resistors for maintaining said mutually spaced relationship between each of the circumferentially wound coil turns; conductor means electrically connecting said first coil ends to said plurality of terminal connections of said one end portion; conductor means electrically connecting said second coil ends to said terminal connections of said other end portion, thereby electrically interconnecting said second coil ends; and conductor means connecting said plurality of terminal connections of said one end portion to said polyphase windings of said rotor, whereby said resistors are connected in a wye-connected rotor resistance circuit and to said polyphase windings of said rotor.

Claim 8

In a wound rotor induction motor, the combination comprising: a frame; a stator carried on said frame; a shaft rotatably supported by said frame and including a shaft extension extending externally of said stator; a rotor secured to said shaft including polyphase windings mounted for rotation adjacent said stator; a support member including a hub mounted on said shaft extension and a fan impeller means extending radially of said hub, said support member further including a pair of end portions extending radially from the ends of said hub, one end portion of said pair of end portions including a plurality of terminal connections insulated from each other and from said one end portion and the other end portion of said pair of end portions being formed of an electrically conductive material and including terminal connections being electrically interconnected by said electrically conductive material; a resistor assembly including plural resistors made of a stainless steel bar material and formed in axially aligned coils formed by coil turns wound circumferentially around said hub and progressing axially in mutually spaced relationship between said pair of end portions of said support member, each of said coils including first and second coil ends which are axially spaced relative to each other and to said pair of end portions of said support member; a plurality of movable mounting assemblies supported for movement relaTive said support member including insulatingly interconnected and spaced-apart stirrup brackets connected to each of said coil turns forming said resistors for maintaining said mutually spaced relationship between each of the circumferentially wound coil turns; conductor means electrically connecting said first coil ends to said plurality of terminal connections of said one end portion; conductor means electrically connecting said second coil ends to said terminal connections of said other end portion, thereby electrically interconnecting said second coil ends; and conductor means connecting said plurality of terminal connections of said one end portion to said polyphase windings of said rotor, whereby said resistors are connected in a wye-connected rotor resistance circuit and to said polyphase windings of said rotor.

Claim 9

In a wound rotor induction motor, the combination comprising: a frame; a stator carried on said frame; a shaft rotatably supported by said frame and including a shaft extension externally of said stator; a rotor secured to said shaft including wye-connected three phase windings mounted for rotation adjacent said stator; three resistors including metal bars forming axially aligned coils formed by plural coil turns extending circumferentially around said shaft extension and progressing axially along said shaft extension whereby said coil turns are mutually axially spaced with said coils respectively terminating in first and second coil ends; a support member including a hub, a pair of axially spaced end portions extending radially outward at the opposite ends of said hub, and circumferentially spaced locations extending axially from said pair of end portions providing supporting surfaces for mounting of said first and second coil ends of said resistors to said support member; a fan means included on said support member including axially extending impellers which develop circulating air through the spaces between said coil turns when said support member is rotated; means for fixedly mounting said first and second coil ends of said resistors to said supporting surfaces of said pair of end portions; a plurality of pivotal linkages each including a pair of parallel pivot arms circumferentially disposed around the outer edges of said pair of end portions of said hub; a bracket assembly for connecting each of said coil turns of said resistors to first ends of said pair of pivot arms; plural counterweight members connected to said second ends of said pair of pivot arms; means for pivotally connecting a middle portion of each of said pair of pivot arms to said pair of end portions of said support member whereby said resistors are mounted to said support member for radially inward and outward movement between said first and second coil ends in response to variations in thermal expansion and to centrifugally developed forces when said shaft is rotated at high speeds and further have a radially inward restraining force applied thereto due to centrifugal force developed on said plural counterweight members when shaft is rotated; and means for respectively connecting said first coil ends of said resistors to each of said three phase windings of said rotor and means electrically interconnecting said second coil ends of said resistors, whereby said resistors form a wye-connected rotor resistance circuit for producing predetermined torque and speed characteristics of said wound rotor induction motor.

Claim 10

In a wound rotor induction motor, the combination comprising: a frame; a stator carried on said frame; a shaft rotatably supported by said frame and including a shaft extension externally of said stator; a rotor secured to said shaft including wye-connected three phase windings mounted for rotation adjacent said stator; three resistors including metal bars forming axially aligned coils formed by plural coil turns extending circumferentially around said shaft extension and progressing axially along said shaft extension whereby said coil turns are mutually axially spaced with said coils respectively terminating in first and second coil ends; a support member including a hub, a pair of axially spaced end portions extending radially outward at the opposite ends of said hub, and circumferentially spaced locations extending axially from said pair of end portions providing supporting surfaces for mounting of said first and second coil ends of said resistors to said support member; a fan means included on said support member including axially extending impellers which develop circulating air through the spaces between said coil turns when said support member is rotated; means for fixedly mounting said first and second coil ends of said resistors to said supporting surfaces of said pair of end portions; a plurality of pivotal linkages each including a pair of parallel pivot arms circumferentially disposed around the outer edges of said pair of end portions of said hub; a bracket assembly for connecting each of said coil turns of said resistors to first ends of said pair of pivot arms; plural counterweight members connected to said second ends of said pair of pivot arms; means for pivotally connecting a middle portion of each of said pair of pivot arms to said pair of end portions of said support member whereby said resistors are mounted to said support member for radially inward and outward movement between said first and second coil ends in response to variations in thermal expansion and to centrifugally developed forces when said shaft is rotated at high speeds and further have a radially inward restraining force applied thereto due to centrifugal force developed on said plural counterweight members when shaft is rotated; and means for respectively connecting said first coil ends of said resistors to each of said three phase windings of said rotor and means electrically interconnecting said second coil ends of said resistors, whereby said resistors form a wye-connected rotor resistance circuit for producing predetermined torque and speed characteristics of said wound rotor induction motor.

Claim 11

In a wound rotor induction motor, the combination comprising: a frame; a stator carried on said frame; a shaft rotatably supported by said frame and including a shaft extension externally of said stator; a rotor secured to said shaft including three phase windings connected in a wye configuration and mounted for rotation adjacent said stator; three resistors formed by metal bars having a predetermined resistance and forming axially aligned coils formed by plural coil turns extending circumferentially around said shaft extension and progressing in axially spaced relationship aLong said shaft extension between first and second coil ends; a support member including a hub, a pair of axially spaced end portions extending radially outward at the opposite ends of said hub with a series of circumferentially spaced pairs of axially aligned hole openings formed adjacent the outer edges of said pair of end portions, and said pair of end portions further including plural circumferentially spaced locations extending axially from the inner sides thereof for providing supporting surfaces for said first and second coil ends; a fan means carried by said support member including axially extending impellers for developing circulating air flow through the spaces between said coil Turns when said support member is rotated; means for fixedly mounting said first and second coil Ends of each of said coils to said supporting surfaces of said pair of end portions; a plurality of pairs of parallel extending pivot arms circumferentially disposed around the outer edges of said pairs of end portions having first and second ends disposed in mutual axial alignment; a bracket assembly including a rodmember connected between said first ends of each pair of pivot arms, said rod member carrying a plurality of annular bushings formed on an insulating material and a plurality of U-shaped stirrup brackets having closed ends and parallel sides extending from said closed ends, each of said closed ends extending over an outer circumferential side portion of one of said coil turns with said parallel sides being clamped between adjacent bushings and to the sides of said coil turns for connecting each of said coil turns to said first ends of said pivot arms, whereby said coil turns are axially interconnected in mutually spaced relationship and supported so as to prevent lateral movement at circumferentially spaced locations; counterweight members formed by elongated bars having ends extending through said pairs of aligned hole openings for limited movement therein and connected to said second ends of said pairs of pivot arms; means for pivotally connecting middle portions of said plurality of pairs of pivot arms to said pair of end portions of said support member whereby said resistors have radially inward restraining forces applied thereto due to centrifugal forces developed on said counterweight members when said shaft is rotated, and further whereby limited pivotal movement of each of said plurality of pairs of pivot arms is provided by the limited movement of said counterweight members, so that said coils have restrained radially inward and outward movement between said first and second coil ends in response to variations in thermal expansion and to centrifugally developed forces when said shaft is rotated at high speeds; and means for respectively electrically connecting said first coil ends to each of said three phase windings of said rotor and means electrically interconnecting said second coil ends, whereby said resistors form a wye-connected rotor resistance circuit for producing predetermined torque and speed characteristics of said wound rotor induction motor.

Claim 12

In a wound rotor induction motor, the combination comprising: a frame; a stator carried on said frame; a shaft rotatably supported by said frame and including a shaft extension externally of said stator; a rotor secured to said shaft including three phase windings connected in a wye configuration and mounted for rotation adjacent said stator; three resistors formed by metal bars having a predetermined resistance and forming axially aligned coils formed by plural coil turns extending circumferentially around said shaft extension and progressing in axially spaced relationship aLong said shaft extension between first and second coil ends; a support member including a hub, a pair of axially spaced end portions extending radially outward at the opposite ends of said hub with a series of circumferentially spaced pairs of axially aligned hole openings formed adjacent the outer edges of said pair of end portions, and said pair of end portions further including plural circumferentially spaced locations extending axially from the inner sides thereof for providing supporting surfaces for said first and second coil ends; a fan means carried by said support member including axially extending impellers for developing circulating air flow through the spaces between said coil Turns when said support member is rotated; means for fixedly mounting said first and second coil Ends of each of said coils to said supporting surfaces of said pair of end portions; a plurality of pairs of parallel extending pivot arms circumferentially disposed around the outer edges of said pairs of end portions having first and second ends disposed in mutual axial alignment; a bracket assembly including a rodmember connected between said first ends of each pair of pivot arms, said rod member carrying a plurality of annular bushings formed on an insulating material and a plurality of U-shaped stirrup brackets having closed ends and parallel sides extending from said closed ends, each of said closed ends extending over an outer circumferential side portion of one of said coil turns with said parallel sides being clamped between adjacent bushings and to the sides of said coil turns for connecting each of said coil turns to said first ends of said pivot arms, whereby said coil turns are axially interconnected in mutually spaced relationship and supported so as to prevent lateral movement at circumferentially spaced locations; counterweight members formed by elongated bars having ends extending through said pairs of aligned hole openings for limited movement therein and connected to said second ends of said pairs of pivot arms; means for pivotally connecting middle portions of said plurality of pairs of pivot arms to said pair of end portions of said support member whereby said resistors have radially inward restraining forces applied thereto due to centrifugal forces developed on said counterweight members when said shaft is rotated, and further whereby limited pivotal movement of each of said plurality of pairs of pivot arms is provided by the limited movement of said counterweight members, so that said coils have restrained radially inward and outward movement between said first and second coil ends in response to variations in thermal expansion and to centrifugally developed forces when said shaft is rotated at high speeds; and means for respectively electrically connecting said first coil ends to each of said three phase windings of said rotor and means electrically interconnecting said second coil ends, whereby said resistors form a wye-connected rotor resistance circuit for producing predetermined torque and speed characteristics of said wound rotor induction motor.