CA1134421A - Insulating sub-slot cover for direct-cooled dynamoelectric machine rotors - Google Patents
Insulating sub-slot cover for direct-cooled dynamoelectric machine rotorsInfo
- Publication number
- CA1134421A CA1134421A CA000329364A CA329364A CA1134421A CA 1134421 A CA1134421 A CA 1134421A CA 000329364 A CA000329364 A CA 000329364A CA 329364 A CA329364 A CA 329364A CA 1134421 A CA1134421 A CA 1134421A
- Authority
- CA
- Canada
- Prior art keywords
- sub
- slot
- slot cover
- rotor
- slots
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
Abstract of the Disclosure The rotating field of a dynamoelectric machine comprises a rotor having electrically conductive windings extending along the axial length of the rotor. The windings are disposed in axially extending slots and the slots include electrical insulation for preventing the transfer of electric current between the windings and the rotor body. A direct cooled generator field is one which is cooled by the atmosphere surrounding the field; e.g., hydrogen or air, and is designed so that the gas coolant is pumped radially through the windings and axially through sub-slots in the rotor body. The present invention is concerned with sub-slot covers which are designed to improve the electrical insulating properties of the cover by increasing the electrical path length between the windings and the rotor body and by obviating the formation of electrical paths due to the possible accumulation of foreign material.
Description
1~34~Z~ 17MT 2695 This invention relates to dynamoelectric machines and, in particular, to direct cooled dynamoelectric machines of the type including a rotating field comprising electrically conductive windings disposed in a plurality of axially extend-ing slots.
The rotating field of a dynamoelectric machine includes a rotor body having a plurality of axially extending slots into which the electrical windings are inserted. The rotor body is generally a steel material whereas the rotor windings comprise a plurality of copper wires. In a direct cooled dynamoelectric machine each slot may further include an axially extending sub-slot for ventilation and cooling.
The direct cooled machine is one which is cooled directly by the atmosphere in which it is disposed; e.g., air or hydrogen. The sub-slots are part of a ventilation scheme, known in the art, for transferring gas coolant axially along the rotor. Each slot also includes provisions for the radial flow of gas coolant primarily through ventilation slots in the windings.
In the afore-described machine it is necessary to electrically insulate the rotor windings from the rotor body such insulation taking the form of non-conductive "slot armor". Moreover, it has been the practice of some manufacturers to provide sub-slot covers which increase the insulation of the bottom of the slot. In a direct cooled dynamoelectric machine wherein the machine coolant is air it is possible that foreign material may accumulate on sub-slot surfaces in such a way as to reduce electrical creepage distances and lead to low insulation resistance or a grounded field.
It is one object of the present invention to provide an improved sub-slot cover for a dynamoelectric ~L~34421 machine rotating field.
It is another object of the present invention to provide an improved sub-slot cover for a dynamoelectric machine field which increases the electrical creepage distances between the field windings and the rotor.
It is still another object of the present inven-tion to provide an improved sub-slot cover for a direct cooled dynamoelectric machine field which reduces the possibility of inadvertent grounding of the field windings which may be caused by the accumulation of foreign deposits.
~he novel features believed characteristic of the present invention are set forth in the appended claims.
The invention itself, however, together with further objects and advantages thereof, may best be understood with reference to the following description taken in connection with the appended drawings.
In accordance with the foregoing objects of the invention a sub-slot cover is formed to be inserted along the axial length of a winding slot. The sub-slot cover is inserted into the slot and the coils are thereafter laid onto the sub-slot cover. One unique feature, of the sub-slot cover construction is a pair of oppositely directed grooves or slots formed on each side of the sub-slot cover and into which one end of the slot armor is inserted.
Interlocking of the slot armor and sub-slot cover extends the length of the electrical creepage path.
A second feature in accordance with one embodiment of the invention is provided by a pair of fins which extend radially inwardly into the sub-slot to interrupt the ~enerally flat configuration of the sub-slot cover thereby increasing once again the electrical creepage path by obviating the accumulation of foreign material on the underside of the ~3 ~42~ 17MT 2695 sub-slot cover.
Figure 1 is an end view of a generator rotor and stator showing in cross-scetion the electrical field and armature windings.
Figure 2 is a prior art showing of a rotor slot and sub-slot including several strands of field windings.
Figure 3 is a cross-section view similar to Figure 2 updating the prior art with one embodiment of the applicant's invention.
Figure 4 is a perspective view of a new sub-slot cover according to the applicant's invention.
Figure 1 shows an end view schematic partially in cross-section of a dynamoelectric machine 11 which includes a frame mounted stationary armature core or stator 13 comprising a plurality of stacked laminations having axially directed electrically conductive armature bars 17 running the length of the machine and terminating in end windings at each of the dynamoelectric machine. The reader will note that only a portion of this well known construction has been shown, the exact details of which are generally available and not particularly germane to the present invention except by way of explanation. The radially inner dovetail slots 19 and the radially outer dovetail slots 21 accommodate stator wedges and keybars respectively (not shown) which maintain the alignment and spacing of stator core laminations. The stator bars carry induced current to the dynamoelectric machine terminals.
A rotor 25 is positioned co-axially within the stator core and includes a cylindrical steel rotor body in which there are a pluarlity of field windings 27. The field windings are electrically conductive members; e.g., copper, which carry excitation current into the dynamoelectric ~ 4421 17MT 2695 machine. The rotor is rotatably supported at each end of the dynamoelectric machine on bearings well known in the art. The field windings are held in place against centrifu-gal forces by dovetail wedges 31.
Referring to Figures 2 and 3, the prior art and the applicant's invention are shown relative to a single rotor winding in that respective order. The drawings show a portion of the rotor steel 41 which has a channel shaped slot 43 formed therein to accept the rotor field windings 27. The windings are current carrying copper wires which must be electrically insulated from the rotor steel.
This is accomplished by so called slot insulation including slot armor 45, a channel shaped piece of glass laminate having spaced ventilation slots 47 along the axial length of the piece. The ventilation slots 47 are in register with radial openings 49 up through the field wlndlngs.
In a direct cooled machine, the field windings are cooled by the surrounding gaseous atmosphere by being pumped radially through the windings and axially through the rotor sub-slots 51. The slot insulation is further enhanced by a sub-slot cover 53 which is interposed between the sub-slot and the slot armor.
In order to understand the advantages of the present invention we must look into the disadvantages of the prior art. The problem involves current leakage paths which might lead to a grounded field. These paths are indicated by the arrows A and B superposed on Figure 2. Arrow A indicates a leakage path between the slot armor 45 and the sub-slot cover 53. Arrow B indicates a leakage path on the radially inner surface of the sub-slot cover, this latter path being a low resistance path ~L~344Zl generated by the deposit of minute particles of foreign matter being thrown in the radially outward direction by centrifugal force. The minute particles are carried into the machine from the surrounding environment by the coolant gas.
The present invention is shown in a preferred embodiment in Figure 4O The sub-slot cover according to the present invention is a substantial]y planar member which includes an upper (radially outer) surface 61 and a lower (radially inner) surface 63. Between the two surfaces, there are two oppositely directed grooves or slots 65 which are made to interlock with the slot armor.
The slots extend along the axial length of the sub-slot cover. Returning to Figure 3, the effect of this construction is to obviate leakage path A demonstrated in Figure 2.
Again, it is the interlock between the grooves in the sub-slot cover and the base legs of the slot armor which forms a part of this invention.
Continuing with the detailed description of the present invention, the lower or radially inner surface of the sub-slot cover is formed with a pair of radially inwardly extending fins 67 which also extend along the axial length of the sub-slot cover. The fins extend radially inwardly into the sub-slot. It will be understood of course that the broad aspects of the inventive concept include embodiments having at least one radially inwardly extending member or fin. The function of the fin is obviously to extend the leakage path based upon that leakage path B indicated in Figure 2.
It is a further, but less apparent function of the fins to provide walls to which minute particles cannot cling as they are flung in the radially outward direction by centrifugal force and hence, the walls become barriers to electrical leakage vis-a-vis path B.
~7~
~1344Zl The improved sub-slot cover is also formed with a ventilation slot 69 and may be made of any suitable insulating material such as glass laminate.
While there has been shown what is considered to be a preferred embodiment of the present invention other modifications may occur to thos having skill in the art. It is intended to cover in the appended claims all such modifications which fall within the true spirit and scope of the claims.
The rotating field of a dynamoelectric machine includes a rotor body having a plurality of axially extending slots into which the electrical windings are inserted. The rotor body is generally a steel material whereas the rotor windings comprise a plurality of copper wires. In a direct cooled dynamoelectric machine each slot may further include an axially extending sub-slot for ventilation and cooling.
The direct cooled machine is one which is cooled directly by the atmosphere in which it is disposed; e.g., air or hydrogen. The sub-slots are part of a ventilation scheme, known in the art, for transferring gas coolant axially along the rotor. Each slot also includes provisions for the radial flow of gas coolant primarily through ventilation slots in the windings.
In the afore-described machine it is necessary to electrically insulate the rotor windings from the rotor body such insulation taking the form of non-conductive "slot armor". Moreover, it has been the practice of some manufacturers to provide sub-slot covers which increase the insulation of the bottom of the slot. In a direct cooled dynamoelectric machine wherein the machine coolant is air it is possible that foreign material may accumulate on sub-slot surfaces in such a way as to reduce electrical creepage distances and lead to low insulation resistance or a grounded field.
It is one object of the present invention to provide an improved sub-slot cover for a dynamoelectric ~L~34421 machine rotating field.
It is another object of the present invention to provide an improved sub-slot cover for a dynamoelectric machine field which increases the electrical creepage distances between the field windings and the rotor.
It is still another object of the present inven-tion to provide an improved sub-slot cover for a direct cooled dynamoelectric machine field which reduces the possibility of inadvertent grounding of the field windings which may be caused by the accumulation of foreign deposits.
~he novel features believed characteristic of the present invention are set forth in the appended claims.
The invention itself, however, together with further objects and advantages thereof, may best be understood with reference to the following description taken in connection with the appended drawings.
In accordance with the foregoing objects of the invention a sub-slot cover is formed to be inserted along the axial length of a winding slot. The sub-slot cover is inserted into the slot and the coils are thereafter laid onto the sub-slot cover. One unique feature, of the sub-slot cover construction is a pair of oppositely directed grooves or slots formed on each side of the sub-slot cover and into which one end of the slot armor is inserted.
Interlocking of the slot armor and sub-slot cover extends the length of the electrical creepage path.
A second feature in accordance with one embodiment of the invention is provided by a pair of fins which extend radially inwardly into the sub-slot to interrupt the ~enerally flat configuration of the sub-slot cover thereby increasing once again the electrical creepage path by obviating the accumulation of foreign material on the underside of the ~3 ~42~ 17MT 2695 sub-slot cover.
Figure 1 is an end view of a generator rotor and stator showing in cross-scetion the electrical field and armature windings.
Figure 2 is a prior art showing of a rotor slot and sub-slot including several strands of field windings.
Figure 3 is a cross-section view similar to Figure 2 updating the prior art with one embodiment of the applicant's invention.
Figure 4 is a perspective view of a new sub-slot cover according to the applicant's invention.
Figure 1 shows an end view schematic partially in cross-section of a dynamoelectric machine 11 which includes a frame mounted stationary armature core or stator 13 comprising a plurality of stacked laminations having axially directed electrically conductive armature bars 17 running the length of the machine and terminating in end windings at each of the dynamoelectric machine. The reader will note that only a portion of this well known construction has been shown, the exact details of which are generally available and not particularly germane to the present invention except by way of explanation. The radially inner dovetail slots 19 and the radially outer dovetail slots 21 accommodate stator wedges and keybars respectively (not shown) which maintain the alignment and spacing of stator core laminations. The stator bars carry induced current to the dynamoelectric machine terminals.
A rotor 25 is positioned co-axially within the stator core and includes a cylindrical steel rotor body in which there are a pluarlity of field windings 27. The field windings are electrically conductive members; e.g., copper, which carry excitation current into the dynamoelectric ~ 4421 17MT 2695 machine. The rotor is rotatably supported at each end of the dynamoelectric machine on bearings well known in the art. The field windings are held in place against centrifu-gal forces by dovetail wedges 31.
Referring to Figures 2 and 3, the prior art and the applicant's invention are shown relative to a single rotor winding in that respective order. The drawings show a portion of the rotor steel 41 which has a channel shaped slot 43 formed therein to accept the rotor field windings 27. The windings are current carrying copper wires which must be electrically insulated from the rotor steel.
This is accomplished by so called slot insulation including slot armor 45, a channel shaped piece of glass laminate having spaced ventilation slots 47 along the axial length of the piece. The ventilation slots 47 are in register with radial openings 49 up through the field wlndlngs.
In a direct cooled machine, the field windings are cooled by the surrounding gaseous atmosphere by being pumped radially through the windings and axially through the rotor sub-slots 51. The slot insulation is further enhanced by a sub-slot cover 53 which is interposed between the sub-slot and the slot armor.
In order to understand the advantages of the present invention we must look into the disadvantages of the prior art. The problem involves current leakage paths which might lead to a grounded field. These paths are indicated by the arrows A and B superposed on Figure 2. Arrow A indicates a leakage path between the slot armor 45 and the sub-slot cover 53. Arrow B indicates a leakage path on the radially inner surface of the sub-slot cover, this latter path being a low resistance path ~L~344Zl generated by the deposit of minute particles of foreign matter being thrown in the radially outward direction by centrifugal force. The minute particles are carried into the machine from the surrounding environment by the coolant gas.
The present invention is shown in a preferred embodiment in Figure 4O The sub-slot cover according to the present invention is a substantial]y planar member which includes an upper (radially outer) surface 61 and a lower (radially inner) surface 63. Between the two surfaces, there are two oppositely directed grooves or slots 65 which are made to interlock with the slot armor.
The slots extend along the axial length of the sub-slot cover. Returning to Figure 3, the effect of this construction is to obviate leakage path A demonstrated in Figure 2.
Again, it is the interlock between the grooves in the sub-slot cover and the base legs of the slot armor which forms a part of this invention.
Continuing with the detailed description of the present invention, the lower or radially inner surface of the sub-slot cover is formed with a pair of radially inwardly extending fins 67 which also extend along the axial length of the sub-slot cover. The fins extend radially inwardly into the sub-slot. It will be understood of course that the broad aspects of the inventive concept include embodiments having at least one radially inwardly extending member or fin. The function of the fin is obviously to extend the leakage path based upon that leakage path B indicated in Figure 2.
It is a further, but less apparent function of the fins to provide walls to which minute particles cannot cling as they are flung in the radially outward direction by centrifugal force and hence, the walls become barriers to electrical leakage vis-a-vis path B.
~7~
~1344Zl The improved sub-slot cover is also formed with a ventilation slot 69 and may be made of any suitable insulating material such as glass laminate.
While there has been shown what is considered to be a preferred embodiment of the present invention other modifications may occur to thos having skill in the art. It is intended to cover in the appended claims all such modifications which fall within the true spirit and scope of the claims.
Claims (5)
1. A sub-slot cover for use in a direct-cooled dynamoelectric machine having a rotor body with axially extending rotor slots for receiving a plurality of electrical conductors;
corresponding, axially extending sub-slots adjoining respective rotor slots and extending radially inwardly therefrom;
and, insulating slot armor for electrically insulating said conductors from said rotor body, said sub-slot cover comprising a substantially planar member positionable between said conductors and a said sub-slot to extend axially along said rotor slot, said member being arranged to permit direct-cooling of said machine, said sub-slot cover having a pair of oppositely directed grooves formed on the edges of said planar member to receive edge portions of said slots armor by insertion therein, whereby an extended length electrical creepage path is provided.
corresponding, axially extending sub-slots adjoining respective rotor slots and extending radially inwardly therefrom;
and, insulating slot armor for electrically insulating said conductors from said rotor body, said sub-slot cover comprising a substantially planar member positionable between said conductors and a said sub-slot to extend axially along said rotor slot, said member being arranged to permit direct-cooling of said machine, said sub-slot cover having a pair of oppositely directed grooves formed on the edges of said planar member to receive edge portions of said slots armor by insertion therein, whereby an extended length electrical creepage path is provided.
2. The sub-slot cover as claimed in claim 1 having at least one fin extending radially inwardly into said sub-slot, whereby the length of the electrical creepage path is further increased.
3. The sub-slot cover as claimed in claim 2 having a plurality of said fins.
4. The sub-slot cover as claimed in claim 3, wherein said fins are arranged on both sides of a longitudinally extend-ing ventilating slot in said planar member.
5. The sub-slot cover as claimed in claim 1 in combination with said direct-cooled dynamoelectric machine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000329364A CA1134421A (en) | 1979-06-08 | 1979-06-08 | Insulating sub-slot cover for direct-cooled dynamoelectric machine rotors |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000329364A CA1134421A (en) | 1979-06-08 | 1979-06-08 | Insulating sub-slot cover for direct-cooled dynamoelectric machine rotors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1134421A true CA1134421A (en) | 1982-10-26 |
Family
ID=4114389
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000329364A Expired CA1134421A (en) | 1979-06-08 | 1979-06-08 | Insulating sub-slot cover for direct-cooled dynamoelectric machine rotors |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1134421A (en) |
-
1979
- 1979-06-08 CA CA000329364A patent/CA1134421A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |