CA1140975A - Permanent magnet alternator with claw type rotor and means to adjust the excitation module - Google Patents
Permanent magnet alternator with claw type rotor and means to adjust the excitation moduleInfo
- Publication number
- CA1140975A CA1140975A CA000339013A CA339013A CA1140975A CA 1140975 A CA1140975 A CA 1140975A CA 000339013 A CA000339013 A CA 000339013A CA 339013 A CA339013 A CA 339013A CA 1140975 A CA1140975 A CA 1140975A
- Authority
- CA
- Canada
- Prior art keywords
- spider
- claws
- permanent magnets
- stator
- excitation module
- 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
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
- H02K21/38—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with rotating flux distributors, and armatures and magnets both stationary
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/30—Structural association with control circuits or drive circuits
- H02K11/33—Drive circuits, e.g. power electronics
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K19/00—Synchronous motors or generators
- H02K19/16—Synchronous generators
- H02K19/36—Structural association of synchronous generators with auxiliary electric devices influencing the characteristic of the generator or controlling the generator, e.g. with impedances or switches
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/70—Wind energy
- Y02E10/72—Wind turbines with rotation axis in wind direction
Abstract
Case 2572 PERMANENT MAGNET ALTERNATOR WITH CLAW TYPE ROTOR
AND MEANS TO ADJUST THE EXCITATION MODULE
ABSTRACT OF THE DISCLOSURE
A dynamoelectric machine and, particularly an alternator, has a claw type rotor in which the magnetic field is induced by permanent magnets. The claw type rotor has a spider of magnetic material secured to the rotor shaft and having a first set of claws on the periphery. An annular disc of magnetic material is mounted to said spider and is spaced axially from said spider by a non-magnetic ring. A second set of claws is on the periphery of the annular disc and these are interleaved with the first set of claws. An excitation module is mounted within the casing of the machine and this module has one surface facing the spider and another facing the annular disc. The permanent magnets are mounted on one of these surfaces, preferably on the surface facing the disc. The magnets thus provide flux across the air gap to the spider to induce poles of one polarity in the first set of claws, and across the air gap to the disc to induce poles of the other polarity in the second set of claws. A
straight axial movement of the excitation module will adjust the air gap at the permanet magnets. A screw arrangement is provided to move the excitation module axially to reduce the attractive forces due to the permanent magnets to aid in assembly and disassembly.
Also, a field winding may be provided on the excitation module to control the flux at the poles during running, and to reduce the attractive force caused by the permanent magnets to aid in assembly and disassembly.
AND MEANS TO ADJUST THE EXCITATION MODULE
ABSTRACT OF THE DISCLOSURE
A dynamoelectric machine and, particularly an alternator, has a claw type rotor in which the magnetic field is induced by permanent magnets. The claw type rotor has a spider of magnetic material secured to the rotor shaft and having a first set of claws on the periphery. An annular disc of magnetic material is mounted to said spider and is spaced axially from said spider by a non-magnetic ring. A second set of claws is on the periphery of the annular disc and these are interleaved with the first set of claws. An excitation module is mounted within the casing of the machine and this module has one surface facing the spider and another facing the annular disc. The permanent magnets are mounted on one of these surfaces, preferably on the surface facing the disc. The magnets thus provide flux across the air gap to the spider to induce poles of one polarity in the first set of claws, and across the air gap to the disc to induce poles of the other polarity in the second set of claws. A
straight axial movement of the excitation module will adjust the air gap at the permanet magnets. A screw arrangement is provided to move the excitation module axially to reduce the attractive forces due to the permanent magnets to aid in assembly and disassembly.
Also, a field winding may be provided on the excitation module to control the flux at the poles during running, and to reduce the attractive force caused by the permanent magnets to aid in assembly and disassembly.
Description
1 Case 2572 PERMANENT MAGNET A~TERNATOR WITH CLAW TYPE ROTO~
AND MEANS TO ADJUST THE EXCITATION MODULE
This invention relates to claw type dynamoelec-tric machines, and in particular it relates to claw type alternators having a field provided by permanent magnets with means to control the field.
Claw type alternators having permanent magnets to generate the active field are known. For example, Canadian Patent No. 773 214 - Tiltins, issued December 5, 1972, describes a claw type alternator structure which may have either a permanent magnet arrangement or a fiéld winding to provide the alternator field.
It is also known to control the flux from a permanent magnet in an alternator. In Canadian Patent No.
793 961 - Rosenberg, issued September 3, 1968, there i~ described, for example, a claw type alternator having permanent magnets mounted on the rotor to generate flux for the alkernator, and a control winding on the stator which is able to adjust or control the flux in the main air gap.
None of the known prior art alternators seem to include a structural arrangement which simplifies adju~tment as well as as~embly and disassembly.
To provide higher efficiencies in alternators which use permanent magnets, it is of course desirable to use magnets with a high field strength. The large magnetic attraction forces associated with the permanent magnets create problems during assembly and disassembly as well as with adjustment of the air gap.
'--~
li4~975 Case 2572 The present invention reduces or eIiminates these problems.
In the present invention the permanent magnets are mounted on a radially extending surface of a stationary module. The magnetic attractive forces are axially directed. The module may be moved axially using jack screws to adjust the air gap. Assembly and disassembly can be carried out using screw adjustment means to move the module inwardly the final part of the distance during assem~ly and to move the module initially outwards during disassembly until the attractive forces diminish to manageable levels.
The present invention also provides a field winding or control winding on the stationary module.
lS The module thus includes the permanent magnets which provide the "normal" excitation and the field coil which provides regulatory excitation, and the module is axially movable as a unit for assembly and disassembly as well as for adjustment of the air gap.
The arrangement of the magnets and the field coil is such that the field coil may be energized during as3embly or disassembly, and the field it generates will reduce the magnetic flux at the poles, due to the permanent magnets, substantially to zero if desired. Thus the magnetic forces may be reduced to manageable levels during assembly and disassembly if desired.
The present invention i9 particularly suited for use with a low speed wind turbine where a substan-tially constant output is desired over a speed rangeof perhaps 70 - 200 RPM. However, it will be apparent that the alternator of the present invention is not restricted to any particular use. The structure which permits easy assembly and disassembly, and also adjustment, may be used in any alternator having 114~)975 Case 2572 permanent magnets and a fieId winding or control winding. The present invention is, in addition, suitable for use in motors as will be apparent to those skilled in the art. In fact, if the invention is incorporated in a synchronous motor, the ~ield winding may be energized for a short time during the starting cycle to assist the motor to accelerate under load.
It is a feature of the present invention to provide a structure for a claw type dynamoeIectric machine having permanent magnets which permits easier assembly, disassembly and adjustment.
It is another feature of the present invention to provide in a claw type dynamoelectric machine, a stationary module which includes both the permanent magnets for providing the main excitation flux and a field winding for regulating the flux in the air gap and which is adjustable and removable as a unit.
It is also a feature of the invention to provide a claw type alternator with a module that is readily assembled and disa9sembled and which includes means to provide a controllable flux.
~ ccordingly in one form of the invention there is provided a dynamoelectric machine comprising, a stator with a stator winding, a claw type rotor having a spider of magnetic material mounted to a shaft for rotation within said stator, said spider having a plurality of first claws spaced around the periphery forming a first set of poles, an annular disc of magnetic material spaced axially from said spider by a non-magnetic material, said annular disc having a plurality of second claws spaced around the periphery and interleaved with said first claws forming a second set of poles, an excitation module having a core of magnetic material with a first radially extending planar surface and a second radially extending planar Case 2572 surface spaced axially from and outwardly with respect to said first surface, and a plurality of permanent magnets on said second surface, said module when in an operating position having said first surface in juxtaposition with said spider forming a first air gap therewith and said permanent magnets in juxtaposition , with said annular disc forming a second air gap therewith, said permanent magnets providing flux to said first claws of one polarity and to said second claws of opposite polarity.
According to another form of the invention there is provided an alternator comprising a casing having a first and second endshield and an intermediate stator shell, a stator core mounted within said stator shell, a stator winding on said stator core, a claw type rotor mounted to a shaft supported by bearings in at least one endshield for rotation within said stator core, said rotor including a spider of magnetic material mounted to said shaft and having a plurality of first claws spaced around the periphery thereof forming a first set of poles, an annular disc of magnetic material spaced axially from said spider by a non-magnetic material, and means mounting said . annular disc to said spider, said annular disc having a plurality of second claws, equal in number to said first claws, spaced around the periphery thereof forming a second set of poles and interleaved with said first claws, a stationary excitation module having a core of magnetic material,with first and second parallel and radially extending surfaces, the second surface being spaced axially from the first surface and being positioned outwardly with respect to said first surface, a plurality of permanent magnets mounted on said second surface, said first surface forming with said spider a first air gap and the Case 2572 magnets on said second surface forming with said annular disc a second air gap, said permanent magnets inducing north magnetic poles in one of said first set of poles or said second set of poles and south magnetic poles in the other.
According to yet another form of the invention there is provided in a dynamoelectric machine having a stator and a stator winding, a claw type rotor having a spider secured to a rotor with first spaced peripheral claws, and an annular disc spaced axially from said spider and fixed thereto with second spaced peripheral claws interleaved with said first claws, said spider and said disc being of magnetic material, an excitation module having a first planar surface facing said spider and a second planar surface facing said annular disc, a plurality of permanent magnets mounted on one of said first or second surfaces, and, means to move said excitation module axially for assembly, disassembly and adjuqtment of the air gap between said magnets and the opposing one of said spider or disc.
The invention will be described in more detail with reference to the accompanying drawings in which Figure 1 is a cross-sectional view of a dynamoelectric machine according to the invention, showing only one half of the machine, and Figure 2 is an isometric overall view of the machine of Figure 1.
Referring now to the drawings an alternator 10 has a casing 11 which includes a stator shell 12 with an upper endshield 14 and a lower endshield lS.
The endshields 14 and 15 are secured to shell 12 with bolts 16 and 17 respectively, spaced around the periphery of the casing. A bearing assembly 18 is mounted inside collar 20 of endshield 14 and supports a shaft 21 for rotation therein. The bearing assembly 11~0975 Case 2572 comprises deep groove ball bearing sets 22 and 23 separated by a spacer 24. A locknut 25 on shaft 21 - retains the bearing assembly 18. Bearing caps 26 and 27 are mounted to collar 20 above and below the bearing assembly 18 with bolts 31. A flinger 28 is mounted to shaft 21 and has a portion extending into a groove or well 30 in bearing cap 27 to fling oil lubricant upwards and outwards away from the shaft.
It is preferred to locate the bearings on one side of the rotor as will become apparent. This not only places the bearings in a region where they will not be subjected to magnetic flux, but it simplifies assembly and disassembly of the flux providing module also as will become apparent subsequently.
Mounted within the stator shell 12 is stator core 32 with stator winding 33. Preferably a series of grooves 34 behind core 32 in shell 12, are provided to form passages for circulating air. The outer surface of shell 12 has radiating fins 35 to assist in radiating or dissipating heat. The cooling of the alternator will be discussed subsequently.
A rotor 36 is mounted to shaft 21. The rotor 36 may be keyed to shaft 21 with a key 37 and retained by a lock ring 38. Other suitable Eastening means may be used.
The rotor 36 comprises a spider 40 of magnetic material having at the outer periphery a plurality of more or less L-shaped claws 41. The claws 41 are spaced apart and form one set of poles. The claws 41 are conveniently integrally formed with spider 40.
An annular disc 42 of magnetic material has at the outer periphery a plurality of more or less L-shaped claws 43. The claws 43 are spaced apart and interleaved with claws 41. The claws 43 are conveniently integrally formed with disc 42 and form 11~0975 Case 2572 the other set of poles. The disc 42 is spaced from spider 40 by a ring 44 of non-magnetic material.
Machine screws or bolts 45 spaced around the spider 40 extend through spider 40 and through ring 44 into disc 42 to mount the disc 42 and ring 44 to spider 40 forming the rotor assembly.
A stationary excitation module 46 comprises a core 47 of magnetic material mounted to end shield 15 by a plurality of bolts 48. The core 47 has a radially extending planar surface 50 on which are mounted a plurality of permanent magnets 51 extending around the planar surface 50 and forming with the adjacent surface of annular disc 42 an air gap 52.
This is the air gap that is adjustable. Core 47 has a recess or well 53 extending around it, the bottom surface of well 53 forming a cylindrical surface at right angles to planar surface 50. A field winding or control winding 54, in the form of a doughnut shaped coil, is mounted in well 53. Field winding 54 may have applied to it a dc current, and the strength and direction of the current determines the strength and direction of the field in core 47. Thus the field coil may provide a flux which aids or opposes the flux from the permanent magnets 51. An opposing flux may be of a strength to substantially prevent magnets 51 from providing excitation flux.
It will be apparent that the magnets could be mounted to the surface of core 47 which faces spider 36. While this alternative is satisfactory, it is not preferred because the area of the air gap surfaces at this location is smaller than the available area at the gap facing the surface of rotor disc 42 since the air gap at rotor disc 42 is at a larger radius or distance from the axis of rotation.
3S When the alternator 10 is operating, the 114~)97S
Case 2572 permanent magnets 51 provide the operating flux to the rotor. Assuming for convenience of description that the permanent magnets have a north pole facing air gap - 52, flux will cross air gap 52, disc 42, and the claws 43 will be north poles. Similarly, there will be a flux path through core 47, across an air gap 55, through spider 40, and the claws ~l will be south poles. As the claws 41 and 43 are interleaved there will be a succession of alternating north and south poles around rotor 36, and as rotor 36 rotates there will be an alternating current generated in stator winding 33.
It should be noted that the permanent magnets 51 are located where they are magnetically shielded from armature reaction effects even up to a condition where a short circuit might occur in the armature winding .
As the speed increase~ over the working speed range of the alternator, the current in field winding 54 is controlled to maintain the output voltage of the alternator substantially constant. When the alternator is used with a wind turbine, it is normally used to charge a battery and it is therefore necessary that the output voltage be kept within preset limits, i.e.
substantially constant over the working range.
Referring for a moment to heat dissipation during operation, heat generated by field winding 54 tends to flow through the heavy magnetic core 47 to casing 11 where it is radiated or removed by air flow over the surface of the casing. Because of its considerable mass, core 47 provides a good heat flow path. The moving rotor 36 causes internal circulation of air generally as indicated by arrows 56. This air flow passes over the end heads of the stator winding, through rotor 36 and through the passage formed by 114~)975 Case 2572 grooves 34. Heat tends to be transferred to shell 12 where it is removed by radiation or by air flow over fins 35. Air can be circulated over shell 12 by an air duct and a fan if desired.
In the assembling of alternator 10, very briefly, the shaft 21 and bearing assembly 18 are positioned in endshield 14 and locknut 25 mounted.
Flinger 28 is installed. Bearing caps 26 and 27 are installed using bolts 31. The rotor 36 including disc 42, ring 44 and both sets of claws is placed on shaft 28, key 37 is positioned and lock ring 38 installed.
The stator shell 12 with core 32 and winding 33 is mounted to endshield 14 using bolts 15. Now the portion so far assembled is fixed with respect to a reference surface by using mounting bracket 57 and bolts 58 indicated in broken lines. The distance is measured from spider 37 and disc 42 to the reference surface. The distance is measured from the exposed end surface of shell 12 i.e. from the outer surface of flanged portion 60 on shell 12 to the reference surface. With these measurements and knowing the dimensions of core 47, magnets 51 and endshield 15, a required measurement for shims 59 to be placed between core 47 and endshield 15 can be determined to provide the required air gaps 52 and 55. When the necessary shimming has been determined, core 47, with field winding 54 and magnets 51 installed, is mounted to endshield 15 with shims 59 in place, using bolts 48. The endshield 15 with the excitation, module 46 (core 47, winding 54 and magnets 51) is now ready to mount.
Referring for the moment to Figure 2, the flanged portions 60 and 61 on the stator shell 12 and the lower endshield 15 respectively, and which are secured by bolts 17 to hold the lower endshield 15 Case 2572 to shell 12~ are also provided with jack screws 62.
There are four jack screws 62, distributed around the flanged portions 60 and 61. Any number of jack screws 62 may of course be used as long as they are sufficient to move the endshield 15 slowly towards shell 12. The jack screws may be threaded into flanged portion 61 and project to engage flanged portion 62.
To continue with the assembly, the jack screws 62 are extended and guide pins placed in at least some of the holes which accommodate bolts 17 to align the bolt holes. It will be recalled that the attractive force caused by the permanent magnets is axial in direction. Now the lower endshield 15 with the excitation module 46 is positioned with the holes for bolts 17 aligned and the jack screws 62 engaging flanged portion 60. The jack screws 62 are then progressively retracted to permit the flanged portion 61 to engage the flanged portion 60. The guide pins are removed and bolts 17 tightened to secure the casing.
In a typical alternator designed, for example, to provide 720 W when rotating at a rated speed of 200 RPM, the magnetic force with the alternator assembled might be of the order of 2000 lb. The working air gap 52 might be of the order of 0.030 inch (0.7620 mm). When this air gap has been enlarged to say 14 times the working air gap, that is to about 0.42 inch (10.668 mm), the magnetic force will have decreased to about 1/200 of the assembled force or about 10 lb. Thus, the jack screws 62 need anly be capable, under these conditions, of operating through a movement of about 0.5 inch (13 mm).
The field winding 54, it will be recalled, is a doughnut shaped coil and it will produce in core 47 a flux which is substantially in either the same . , 1~4~975 Case 2572 direction or in the opposite direction to the flux from the permanent magnets 51. Thus, if preferred, the field winding 54 can be energized to reduce the resultant flux to substantially zero prior to assembling the endshield 15 with excitation module 46 to the remainder of the alternator. The same technique, in reverse, can be used for disassembly. This makes assembly and disassembly much easier provided the permanent magnets 51 can withstand the reverse excitation. This will depend on the material of the permanent magnets. A cobalt rare earth magnet is able to withstand such reverse excitation.
It was previously mentioned that the present invention could be used in a motor and this will now be apparent. When the machine described is used as a motor, the field winding 54 is obviously used for a different purpose as there is no output voltage to regulate. The invention is directed primarily to a structure which provides a simpler assembly and disassembly and thiC is available in a dynamoelectric machine of the type described uRed either as an alternator or as a motor. The field winding may be used to aid assembly and disassembly whether in an alternator or motor. Also, in an alternator, the field winding can regulate voltage and in a motor it can be used to assist starting.
Other advantages and uses may be apparent to those Rkilled in the art.
AND MEANS TO ADJUST THE EXCITATION MODULE
This invention relates to claw type dynamoelec-tric machines, and in particular it relates to claw type alternators having a field provided by permanent magnets with means to control the field.
Claw type alternators having permanent magnets to generate the active field are known. For example, Canadian Patent No. 773 214 - Tiltins, issued December 5, 1972, describes a claw type alternator structure which may have either a permanent magnet arrangement or a fiéld winding to provide the alternator field.
It is also known to control the flux from a permanent magnet in an alternator. In Canadian Patent No.
793 961 - Rosenberg, issued September 3, 1968, there i~ described, for example, a claw type alternator having permanent magnets mounted on the rotor to generate flux for the alkernator, and a control winding on the stator which is able to adjust or control the flux in the main air gap.
None of the known prior art alternators seem to include a structural arrangement which simplifies adju~tment as well as as~embly and disassembly.
To provide higher efficiencies in alternators which use permanent magnets, it is of course desirable to use magnets with a high field strength. The large magnetic attraction forces associated with the permanent magnets create problems during assembly and disassembly as well as with adjustment of the air gap.
'--~
li4~975 Case 2572 The present invention reduces or eIiminates these problems.
In the present invention the permanent magnets are mounted on a radially extending surface of a stationary module. The magnetic attractive forces are axially directed. The module may be moved axially using jack screws to adjust the air gap. Assembly and disassembly can be carried out using screw adjustment means to move the module inwardly the final part of the distance during assem~ly and to move the module initially outwards during disassembly until the attractive forces diminish to manageable levels.
The present invention also provides a field winding or control winding on the stationary module.
lS The module thus includes the permanent magnets which provide the "normal" excitation and the field coil which provides regulatory excitation, and the module is axially movable as a unit for assembly and disassembly as well as for adjustment of the air gap.
The arrangement of the magnets and the field coil is such that the field coil may be energized during as3embly or disassembly, and the field it generates will reduce the magnetic flux at the poles, due to the permanent magnets, substantially to zero if desired. Thus the magnetic forces may be reduced to manageable levels during assembly and disassembly if desired.
The present invention i9 particularly suited for use with a low speed wind turbine where a substan-tially constant output is desired over a speed rangeof perhaps 70 - 200 RPM. However, it will be apparent that the alternator of the present invention is not restricted to any particular use. The structure which permits easy assembly and disassembly, and also adjustment, may be used in any alternator having 114~)975 Case 2572 permanent magnets and a fieId winding or control winding. The present invention is, in addition, suitable for use in motors as will be apparent to those skilled in the art. In fact, if the invention is incorporated in a synchronous motor, the ~ield winding may be energized for a short time during the starting cycle to assist the motor to accelerate under load.
It is a feature of the present invention to provide a structure for a claw type dynamoeIectric machine having permanent magnets which permits easier assembly, disassembly and adjustment.
It is another feature of the present invention to provide in a claw type dynamoelectric machine, a stationary module which includes both the permanent magnets for providing the main excitation flux and a field winding for regulating the flux in the air gap and which is adjustable and removable as a unit.
It is also a feature of the invention to provide a claw type alternator with a module that is readily assembled and disa9sembled and which includes means to provide a controllable flux.
~ ccordingly in one form of the invention there is provided a dynamoelectric machine comprising, a stator with a stator winding, a claw type rotor having a spider of magnetic material mounted to a shaft for rotation within said stator, said spider having a plurality of first claws spaced around the periphery forming a first set of poles, an annular disc of magnetic material spaced axially from said spider by a non-magnetic material, said annular disc having a plurality of second claws spaced around the periphery and interleaved with said first claws forming a second set of poles, an excitation module having a core of magnetic material with a first radially extending planar surface and a second radially extending planar Case 2572 surface spaced axially from and outwardly with respect to said first surface, and a plurality of permanent magnets on said second surface, said module when in an operating position having said first surface in juxtaposition with said spider forming a first air gap therewith and said permanent magnets in juxtaposition , with said annular disc forming a second air gap therewith, said permanent magnets providing flux to said first claws of one polarity and to said second claws of opposite polarity.
According to another form of the invention there is provided an alternator comprising a casing having a first and second endshield and an intermediate stator shell, a stator core mounted within said stator shell, a stator winding on said stator core, a claw type rotor mounted to a shaft supported by bearings in at least one endshield for rotation within said stator core, said rotor including a spider of magnetic material mounted to said shaft and having a plurality of first claws spaced around the periphery thereof forming a first set of poles, an annular disc of magnetic material spaced axially from said spider by a non-magnetic material, and means mounting said . annular disc to said spider, said annular disc having a plurality of second claws, equal in number to said first claws, spaced around the periphery thereof forming a second set of poles and interleaved with said first claws, a stationary excitation module having a core of magnetic material,with first and second parallel and radially extending surfaces, the second surface being spaced axially from the first surface and being positioned outwardly with respect to said first surface, a plurality of permanent magnets mounted on said second surface, said first surface forming with said spider a first air gap and the Case 2572 magnets on said second surface forming with said annular disc a second air gap, said permanent magnets inducing north magnetic poles in one of said first set of poles or said second set of poles and south magnetic poles in the other.
According to yet another form of the invention there is provided in a dynamoelectric machine having a stator and a stator winding, a claw type rotor having a spider secured to a rotor with first spaced peripheral claws, and an annular disc spaced axially from said spider and fixed thereto with second spaced peripheral claws interleaved with said first claws, said spider and said disc being of magnetic material, an excitation module having a first planar surface facing said spider and a second planar surface facing said annular disc, a plurality of permanent magnets mounted on one of said first or second surfaces, and, means to move said excitation module axially for assembly, disassembly and adjuqtment of the air gap between said magnets and the opposing one of said spider or disc.
The invention will be described in more detail with reference to the accompanying drawings in which Figure 1 is a cross-sectional view of a dynamoelectric machine according to the invention, showing only one half of the machine, and Figure 2 is an isometric overall view of the machine of Figure 1.
Referring now to the drawings an alternator 10 has a casing 11 which includes a stator shell 12 with an upper endshield 14 and a lower endshield lS.
The endshields 14 and 15 are secured to shell 12 with bolts 16 and 17 respectively, spaced around the periphery of the casing. A bearing assembly 18 is mounted inside collar 20 of endshield 14 and supports a shaft 21 for rotation therein. The bearing assembly 11~0975 Case 2572 comprises deep groove ball bearing sets 22 and 23 separated by a spacer 24. A locknut 25 on shaft 21 - retains the bearing assembly 18. Bearing caps 26 and 27 are mounted to collar 20 above and below the bearing assembly 18 with bolts 31. A flinger 28 is mounted to shaft 21 and has a portion extending into a groove or well 30 in bearing cap 27 to fling oil lubricant upwards and outwards away from the shaft.
It is preferred to locate the bearings on one side of the rotor as will become apparent. This not only places the bearings in a region where they will not be subjected to magnetic flux, but it simplifies assembly and disassembly of the flux providing module also as will become apparent subsequently.
Mounted within the stator shell 12 is stator core 32 with stator winding 33. Preferably a series of grooves 34 behind core 32 in shell 12, are provided to form passages for circulating air. The outer surface of shell 12 has radiating fins 35 to assist in radiating or dissipating heat. The cooling of the alternator will be discussed subsequently.
A rotor 36 is mounted to shaft 21. The rotor 36 may be keyed to shaft 21 with a key 37 and retained by a lock ring 38. Other suitable Eastening means may be used.
The rotor 36 comprises a spider 40 of magnetic material having at the outer periphery a plurality of more or less L-shaped claws 41. The claws 41 are spaced apart and form one set of poles. The claws 41 are conveniently integrally formed with spider 40.
An annular disc 42 of magnetic material has at the outer periphery a plurality of more or less L-shaped claws 43. The claws 43 are spaced apart and interleaved with claws 41. The claws 43 are conveniently integrally formed with disc 42 and form 11~0975 Case 2572 the other set of poles. The disc 42 is spaced from spider 40 by a ring 44 of non-magnetic material.
Machine screws or bolts 45 spaced around the spider 40 extend through spider 40 and through ring 44 into disc 42 to mount the disc 42 and ring 44 to spider 40 forming the rotor assembly.
A stationary excitation module 46 comprises a core 47 of magnetic material mounted to end shield 15 by a plurality of bolts 48. The core 47 has a radially extending planar surface 50 on which are mounted a plurality of permanent magnets 51 extending around the planar surface 50 and forming with the adjacent surface of annular disc 42 an air gap 52.
This is the air gap that is adjustable. Core 47 has a recess or well 53 extending around it, the bottom surface of well 53 forming a cylindrical surface at right angles to planar surface 50. A field winding or control winding 54, in the form of a doughnut shaped coil, is mounted in well 53. Field winding 54 may have applied to it a dc current, and the strength and direction of the current determines the strength and direction of the field in core 47. Thus the field coil may provide a flux which aids or opposes the flux from the permanent magnets 51. An opposing flux may be of a strength to substantially prevent magnets 51 from providing excitation flux.
It will be apparent that the magnets could be mounted to the surface of core 47 which faces spider 36. While this alternative is satisfactory, it is not preferred because the area of the air gap surfaces at this location is smaller than the available area at the gap facing the surface of rotor disc 42 since the air gap at rotor disc 42 is at a larger radius or distance from the axis of rotation.
3S When the alternator 10 is operating, the 114~)97S
Case 2572 permanent magnets 51 provide the operating flux to the rotor. Assuming for convenience of description that the permanent magnets have a north pole facing air gap - 52, flux will cross air gap 52, disc 42, and the claws 43 will be north poles. Similarly, there will be a flux path through core 47, across an air gap 55, through spider 40, and the claws ~l will be south poles. As the claws 41 and 43 are interleaved there will be a succession of alternating north and south poles around rotor 36, and as rotor 36 rotates there will be an alternating current generated in stator winding 33.
It should be noted that the permanent magnets 51 are located where they are magnetically shielded from armature reaction effects even up to a condition where a short circuit might occur in the armature winding .
As the speed increase~ over the working speed range of the alternator, the current in field winding 54 is controlled to maintain the output voltage of the alternator substantially constant. When the alternator is used with a wind turbine, it is normally used to charge a battery and it is therefore necessary that the output voltage be kept within preset limits, i.e.
substantially constant over the working range.
Referring for a moment to heat dissipation during operation, heat generated by field winding 54 tends to flow through the heavy magnetic core 47 to casing 11 where it is radiated or removed by air flow over the surface of the casing. Because of its considerable mass, core 47 provides a good heat flow path. The moving rotor 36 causes internal circulation of air generally as indicated by arrows 56. This air flow passes over the end heads of the stator winding, through rotor 36 and through the passage formed by 114~)975 Case 2572 grooves 34. Heat tends to be transferred to shell 12 where it is removed by radiation or by air flow over fins 35. Air can be circulated over shell 12 by an air duct and a fan if desired.
In the assembling of alternator 10, very briefly, the shaft 21 and bearing assembly 18 are positioned in endshield 14 and locknut 25 mounted.
Flinger 28 is installed. Bearing caps 26 and 27 are installed using bolts 31. The rotor 36 including disc 42, ring 44 and both sets of claws is placed on shaft 28, key 37 is positioned and lock ring 38 installed.
The stator shell 12 with core 32 and winding 33 is mounted to endshield 14 using bolts 15. Now the portion so far assembled is fixed with respect to a reference surface by using mounting bracket 57 and bolts 58 indicated in broken lines. The distance is measured from spider 37 and disc 42 to the reference surface. The distance is measured from the exposed end surface of shell 12 i.e. from the outer surface of flanged portion 60 on shell 12 to the reference surface. With these measurements and knowing the dimensions of core 47, magnets 51 and endshield 15, a required measurement for shims 59 to be placed between core 47 and endshield 15 can be determined to provide the required air gaps 52 and 55. When the necessary shimming has been determined, core 47, with field winding 54 and magnets 51 installed, is mounted to endshield 15 with shims 59 in place, using bolts 48. The endshield 15 with the excitation, module 46 (core 47, winding 54 and magnets 51) is now ready to mount.
Referring for the moment to Figure 2, the flanged portions 60 and 61 on the stator shell 12 and the lower endshield 15 respectively, and which are secured by bolts 17 to hold the lower endshield 15 Case 2572 to shell 12~ are also provided with jack screws 62.
There are four jack screws 62, distributed around the flanged portions 60 and 61. Any number of jack screws 62 may of course be used as long as they are sufficient to move the endshield 15 slowly towards shell 12. The jack screws may be threaded into flanged portion 61 and project to engage flanged portion 62.
To continue with the assembly, the jack screws 62 are extended and guide pins placed in at least some of the holes which accommodate bolts 17 to align the bolt holes. It will be recalled that the attractive force caused by the permanent magnets is axial in direction. Now the lower endshield 15 with the excitation module 46 is positioned with the holes for bolts 17 aligned and the jack screws 62 engaging flanged portion 60. The jack screws 62 are then progressively retracted to permit the flanged portion 61 to engage the flanged portion 60. The guide pins are removed and bolts 17 tightened to secure the casing.
In a typical alternator designed, for example, to provide 720 W when rotating at a rated speed of 200 RPM, the magnetic force with the alternator assembled might be of the order of 2000 lb. The working air gap 52 might be of the order of 0.030 inch (0.7620 mm). When this air gap has been enlarged to say 14 times the working air gap, that is to about 0.42 inch (10.668 mm), the magnetic force will have decreased to about 1/200 of the assembled force or about 10 lb. Thus, the jack screws 62 need anly be capable, under these conditions, of operating through a movement of about 0.5 inch (13 mm).
The field winding 54, it will be recalled, is a doughnut shaped coil and it will produce in core 47 a flux which is substantially in either the same . , 1~4~975 Case 2572 direction or in the opposite direction to the flux from the permanent magnets 51. Thus, if preferred, the field winding 54 can be energized to reduce the resultant flux to substantially zero prior to assembling the endshield 15 with excitation module 46 to the remainder of the alternator. The same technique, in reverse, can be used for disassembly. This makes assembly and disassembly much easier provided the permanent magnets 51 can withstand the reverse excitation. This will depend on the material of the permanent magnets. A cobalt rare earth magnet is able to withstand such reverse excitation.
It was previously mentioned that the present invention could be used in a motor and this will now be apparent. When the machine described is used as a motor, the field winding 54 is obviously used for a different purpose as there is no output voltage to regulate. The invention is directed primarily to a structure which provides a simpler assembly and disassembly and thiC is available in a dynamoelectric machine of the type described uRed either as an alternator or as a motor. The field winding may be used to aid assembly and disassembly whether in an alternator or motor. Also, in an alternator, the field winding can regulate voltage and in a motor it can be used to assist starting.
Other advantages and uses may be apparent to those Rkilled in the art.
Claims (8)
1. A dynamoelectric machine comprising, a stator with a stator winding, a claw type rotor having a spider of magnetic material mounted to a shaft for rotation within said stator, said spider having a plurality of first claws spaced around the periphery forming a first set of poles, an annular disc of magnetic material spaced axially from said spider by a non-magnetic material, said annular disc having a plurality of second claws spaced around the periphery and interleaved with said first claws forming a second set of poles, an excitation module having a core of magnetic material with a first radially extending planar surface and a second radially extending planar surface spaced axially from and outwardly with respect to said first surface, and a plurality of permanent magnets on said second surface, said module when in an operating position having said first surface in juxtaposition with said spider forming a first air gap therewith and said permanent magnets in juxtaposition with said annular disc forming a second air gap therewith, said permanent magnets providing flux to said first claws of one polarity and to said second claws of opposite polarity, and means to move said excitation module axially between said operating position and a remote position where said first and second air gaps are increased by several times to reduce the magnetic attractive forces and permit easier assembly and disassembly.
2. A dynamoelectric machine as defined in claim 1 in which said stator is mounted to a stator shell and said excitation module is mounted to an endshield, said stator shell and endshield abutting when in operating position to form a portion of a casing, and having means to secure the abutted shell and endshield together, and in 13 Case 2572 which said means to move said excitation module axially comprises a plurality of jack screws spaced around the abutting portion of said shell and endshield, said jack screws operating to move said shell and endshield apart and together for disassembly and assembly.
3. A dynamoelectric machine as defined in claim 1 in which said core of said excitation module is provided with a core receiving recess and a field winding mounted in said recess, said field winding when energized providing a magnetic field which in said core is substantially in the same path as that provided by said permanent magnets whereby energization of said field winding can provide a field to control the flux at said first and second claws and to reduce the magnetic attractive forces created by said permanent mangets to permit easier assembly and disassembly.
4. A dynamoelectric machine as defined in claim 1, 2 or 3 in which said annular disc is spaced from said spider by a cylindrical ring of non-magnetic material through which a non-magnetic fastener extends securing said disc and spider together with said ring between.
5. An alternator comprising a casing having a first and second endshield and an intermediate stator shell, a stator core mounted within said stator shell, a stator winding on said stator core, a claw type rotor mounted to shaft supported by bearings in at least one endshield for rotation within said stator core, said rotor including a spider of magnetic material mounted to said shaft and having a plurality of first claws spaced around the periphery thereof forming a first set of poles, an annular disc of magnetic material spaced axially from said spider by a non-magnetic material, and means mounted said annular disc to said spider, said annular disc having a plurality of second claws, equal in number to said first claws, spaced around the periphery therof forming a second set of poles and interleaved with said first claws, 14 Case 2572 a stationary excitation module having a core of magnetic material with first and second parallel and radially extending surfaces, the second surface being spaced axially from the first surface and being positioned outwardly with respect to said first surface, a plurality of permanent magnets mounted on said second surface, said first surface forming with said spider a first air gap and the magnets on said second surface forming with said annular disc a second air gap, said permanent magnets inducing north magnetic poles in one of said first set of poles or said second set of poles and south magnetic poles in the other, said excitation module is mounted to said second endshield, and screw means engaging said stator shell and said second endshield for axially separating said stator shell and said second endshield to reduce the effect of attractive forces due to said permanent magnets.
6. An alternator as defined in claim 5 and further comprising an annular core receiving recess in said core of said excitation module between said first and second surfaces and a field winding mounted in said recess, said field wind-ing when energized providing in said core of said excitation module a magnetic field for opposing and reinforcing the field due to said permanent magnets, said field winding being energized to provide a field opposing the field due to said permanent magnets to reduce the effect of attractive forces of said permanent magnets for ease of assembly and disassembly.
7. In a dynamoelectric machine having a stator and a stator winding, a claw type rotor having a spider secured to a rotor shaft, said spider having first spaced peripheral claws, and an annular disc spaced axially from said spider and fixed with respect to said spider, said annular disc having second spaced peripheral claws interleaved with said first claws, said spider and said disc being of magnetic material, Case 2572 an excitation module having a first planar surface facing said spider and a second planar surface facing said annular disc, a plurality of permanent magnets mounted on one of said first or second surfaces, and, means to move said excitation module axially for assembly, disassembly and adjustment of the air gap between said magnets and the opposing one of said spider or disc.
8. A dynamoelectric machine as claimed in claim 7 in which said first and second planar surfaces are paralle.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000339013A CA1140975A (en) | 1979-11-02 | 1979-11-02 | Permanent magnet alternator with claw type rotor and means to adjust the excitation module |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000339013A CA1140975A (en) | 1979-11-02 | 1979-11-02 | Permanent magnet alternator with claw type rotor and means to adjust the excitation module |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1140975A true CA1140975A (en) | 1983-02-08 |
Family
ID=4115520
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000339013A Expired CA1140975A (en) | 1979-11-02 | 1979-11-02 | Permanent magnet alternator with claw type rotor and means to adjust the excitation module |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1140975A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2582164A1 (en) * | 1985-05-20 | 1986-11-21 | Tecumseh Products Co | COMPRESSOR ALTERNATOR WITH PERMANENT MAGNET EXCITATION AND DIRECT CURRENT CONTROL |
| CN114530958A (en) * | 2022-03-29 | 2022-05-24 | 江西泰豪军工集团有限公司 | Claw-pole generator |
| US20220360154A1 (en) * | 2021-05-10 | 2022-11-10 | General Electric Renovables Espana, S.L. | Armature assemblies for generators and assembly methods |
-
1979
- 1979-11-02 CA CA000339013A patent/CA1140975A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2582164A1 (en) * | 1985-05-20 | 1986-11-21 | Tecumseh Products Co | COMPRESSOR ALTERNATOR WITH PERMANENT MAGNET EXCITATION AND DIRECT CURRENT CONTROL |
| US20220360154A1 (en) * | 2021-05-10 | 2022-11-10 | General Electric Renovables Espana, S.L. | Armature assemblies for generators and assembly methods |
| CN114530958A (en) * | 2022-03-29 | 2022-05-24 | 江西泰豪军工集团有限公司 | Claw-pole generator |
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