Abstract:
A method of assembling a power tool, a power tool, a method of assembling an electrical device, and an electrical device includes a switched reluctance motor. The electrical device is preferably a hand-held power tool, however, any type of electrical device that includes a switched reluctance motor may benefit from any number of aspects of the invention. In one independent aspect, the invention provides a construction that reduces tolerance stack-up. In another independent aspect, the invention provides a self-contained electronics package that plugs into a switched reluctance motor to provide control operation of the switched reluctance motor. In another independent aspect, the invention provides enhanced cooling that increases the efficiency of the electrical device using a switched reluctance motor. In another independent aspect, the invention provides an encapsulated magnet that allows for contaminant free motor control over the life of the SR motor. In another independent aspect, the invention provides an apparatus and a method for aligning magnets of a magnet hub with respect to the rotor poles the magnet poles represent.

Description:
RELATED APPLICATIONS 
   This application is a continuation of prior filed patent application Ser. No. 10/357,729; filed on Feb. 4, 2003, now U.S. Pat. No. 7,064,462 which claims the benefit of Provisional Patent Application Ser. No. 60/354,253, filed Feb. 4, 2002, the entire contents of both of which are incorporated by reference herein. 

   FIELD OF THE INVENTION 
   The present invention relates to electrical devices that include a switched reluctance (“SR”) motor and, more particularly, to power tools that include a SR motor. 
   BACKGROUND OF THE INVENTION 
   A typical SR motor includes multiple salient poles on both the stator and the rotor. Windings or coils are wound on the stator poles, and each pair of windings on diametrically opposite stator poles are connected in series or in parallel to form an electrically independent phase of the SR motor. The rotor is made of a magnetically permeable material such as, for example, a ferrous alloy. Electronics are utilized to energize the independent phases of the SR motor which thereby produce a magnetic field that interacts with the rotor poles to turn the rotor and the shaft to which the rotor is attached. 
   The simple design of SR motors is a feature which allows SR motors to generally last longer than other types of motors that are used in electrical devices. SR motors do not utilize permanent magnets, brushes and/or commutators as are typically used on the other types of motors. Elimination of these components reduces the maintenance needs and increases the life span of the SR motor when compared with the other types of motors. 
   SR motors also offer a number of other benefits over the other types of motors. These benefits include increased performance and a rugged construction for harsh environments. SR motors generally produce more torque than similarly sized models of the other types of motors. SR motors include efficiencies that are consistent over a wider range of operation and that are at least as good as the other types of motors. SR motors also include high speed and high acceleration capabilities. The benefits of SR motors make the use of SR motors desirable in a wide variety of electrical devices. 
   SUMMARY OF THE INVENTION 
   One type of electrical device that can benefit from the use of SR motors includes power tools and, more particularly, power tools configured to be hand-held during operation (“hand-held power tools”). Hand-held power tools generally include, for example, drills, circular saws, grinders, reciprocating saws, sanders, etc. These power tools typically include a housing that supports a drive unit (e.g., an electric motor) that is powered by a power source (e.g., an alternating current (“AC”) corded power and/or a direct current (“DC”) battery power) to drive a driven unit (e.g., a gearbox and an associated driven element such as a drill bit). The drive unit for these power tools is commonly a universal motor. 
   Although SR motors provide a number of benefits over the types of drive units currently used in hand-held power tools, a number of constraints have kept the SR motor from being utilized as a drive unit for such hand-held power tools. Hand-held power tools inherently need to be small enough that the operator can comfortably support and control the tool. Size and weight considerations typically dictate that such a power tool can be operated using a single hand under normal conditions. Some larger and more powerful hand-held power tools (e.g., a rotary hammer) may require two hands for operation. Regardless of the number of hands required for operation, space within the housing of these hand-held power tools is always a design consideration. 
   The small space design considerations result in problems when attempting to integrate a SR motor and the electronics associated with the SR motor into a hand-held power tool. The independent problems include, among others, those associated with heat dissipation, electrical noise, manufacturing tolerances, etc. SR motors are commonly used in applications including washing machines, compressors, blower units, automotive applications, etc. The space available in these applications commonly allows designers to integrate SR motors and the electronics associated with the SR motors into the device without experiencing many of the independent problems noted above with respect to the use of a SR motor and its associated electronics in a hand-held power tool. 
   Accordingly, in some aspects, the invention provides a hand-held power tool including a switched reluctance motor which substantially alleviates one or more of the above-described and other independent problems with existing SR motors and hand-held power tools. 
   In some aspects and in some constructions, the invention provides a construction that reduces tolerance stack-up. Manufacturing techniques that result in increased tolerance stack-up generally require components that have tolerances that are tighter than those tolerances required when increased tolerance stack-up is not present. Tighter tolerances therefore often correspond with higher manufacturing costs which thereby increase the overall cost of the electrical device the SR motor is integrated in. 
   In some aspects and in some constructions, the invention provides a self-contained electronics package that plugs into a SR motor to provide control functions to the SR motor. The electronics package can be quickly replaced and/or removed for service. 
   In some aspects and in some constructions, the invention provides enhanced cooling that keeps the electronics and the components of the SR motor cool for efficient operation. 
   In some aspects and in some constructions, the invention provides an encapsulated magnet that allows for contaminant free motor control over the life of the SR motor. The magnet is physically protected from contaminants such that contaminants cannot form on the magnet and thereby affect the motor control. 
   In some aspects and in some constructions, the invention provides an apparatus and a method for aligning magnet poles of a magnet hub with respect to the rotor poles the magnet poles represent. 
   The aspects of the invention that alleviate the integration problems for hand-held power tools may also provide benefits in electrical devices other than hand-held power tools. For example, the aspects may increase the efficiencies of the operation of SR motors used in other electrical devices and/or reduce costs associated with producing and/or servicing the SR motors and the electronics associated with the SR motors of the other electrical devices. Additionally, some aspects of the invention may further be applicable for use in electrical devices that utilize other types of motors. 
   It is an independent advantage of the invention to provide a power tool that is configured to be hand-held during operation that is driven by a switched reluctance motor. It is an independent advantage of the invention to provide a construction that reduces tolerance stack-up. Also, it is an independent advantage of the invention to provide a self-contained electronics package that plugs into a SR motor to provide control functions to the SR motor. In addition, it is an independent advantage of the invention to provide enhanced cooling that keeps the electronics and the components of the SR motor cool for efficient operation. Further, it is an independent advantage of the invention to provide an encapsulated magnet that allows for contaminant free motor control over the life of the SR motor. It is an independent advantage to provide an apparatus and a method for aligning magnet poles of a magnet hub with respect to the rotor poles the magnet poles represent. 
   Other independent features and independent advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  is a perspective view of an electrical device embodying the invention. 
       FIG. 2  is a simplified schematic representation of a switched reluctance motor. 
       FIGS. 3A ,  3 B, and  3 C illustrate a rotor construction of the switched reluctance motor of  FIG. 2 . 
       FIG. 4  illustrates a perspective view of a stator of the switched reluctance motor of  FIG. 2 . 
       FIGS. 5A ,  5 B, and  5 C illustrate a stator construction of the switched reluctance motor of  FIG. 2 . 
       FIG. 6  illustrates a perspective view of a rotor assembly of the electrical device illustrated in  FIG. 1 . 
       FIG. 7  illustrates the rotor assembly of  FIG. 6  including a magnet hub and a shaft tube. 
       FIG. 8  illustrates an exploded view of the rotor assembly of  FIG. 7 . 
       FIG. 9  illustrates a side view of the rotor assembly of  FIG. 7 . 
       FIGS. 10 and 11  illustrate perspective views of a stator assembly of the electrical device illustrated in  FIG. 1 . 
       FIG. 12  illustrates an exploded view of the stator assembly of  FIGS. 10 and 11 . 
       FIGS. 13A and 13B  illustrate a side and an end view of the stator assembly of  FIGS. 10 and 11 . 
       FIGS. 14A ,  14 B,  14 C,  14 D,  14 E, and  14 F illustrate a rear bell of the stator assembly of  FIGS. 10 and 11 . 
       FIGS. 15 and 16  illustrate partial sectional views of the electrical device illustrated in  FIG. 1 . 
       FIGS. 17A and 17B  illustrate an end and a side view of a terminal board of the stator assembly of  FIGS. 10 and 11 . 
       FIGS. 18A ,  18 B,  18 C, and  18 D illustrate a front bell of the stator assembly of  FIGS. 10 and 11 . 
       FIGS. 19A-C  illustrate a schematic diagram of an electronics package of the electrical device of  FIG. 1 . 
       FIG. 20  illustrates a perspective view of a first printed circuit board of the electronics package illustrated in  FIGS. 19A-C . 
       FIG. 21  illustrates a perspective view of a second printed circuit board of the electronics package illustrated in  FIGS. 19A-C . 
       FIGS. 22 and 23  illustrate partial assemblies of the electrical device illustrated in  FIG. 1 . 
       FIG. 24  illustrates a fixture for coupling a magnet hub to a rotor assembly. 
       FIGS. 25 ,  26 ,  27 ,  28 , and  29  illustrate an alternate construction of a portion of the electrical device illustrated in  FIG. 1   
       FIG. 30  is a perspective view of an electrical device embodying the invention. 
       FIGS. 31 and 32  illustrate perspective views of a rotor assembly of the electrical device illustrated in  FIG. 30 . 
       FIGS. 33 and 34  illustrates perspective views of a stator assembly of the electrical device illustrated in  FIG. 30 . 
       FIG. 35  illustrates a partial sectional view of the electrical device illustrated in  FIG. 30 . 
       FIG. 36  illustrates a perspective view of a printed circuit board of the electrical device illustrated in  FIG. 30 . 
       FIGS. 37 and 38  illustrate partial assemblies of the electrical device illustrated in  FIG. 30 . 
   

   Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
   DETAILED DESCRIPTION 
     FIG. 1  illustrates an electrical device  100  embodying aspects of the invention. In the illustrated construction and in some aspects, the electrical device  100  is a power tool, and, more particularly, a power tool configured to be hand-held during operation (i.e., the electrical device  100  is a power tool designed to be supported by an operator, and not normally supported on a surface, such as a workbench, during operation). In the illustrated construction, the electrical device  100  is a reciprocating saw. It should be understood that aspects of the invention apply equally to any electrical device that includes a SR motor, such as, for example other power tools configured to be hand-held during operation (e.g., drills, circular saws, grinders, reciprocating saws, sanders, caulk guns, jigsaws, screwdrivers, heat guns, impact wrenches, shears, nibblers, rotary hammers, routers, hand planers, plate jointers, rotary tools, etc.), power tools not configured to be hand-held during operation (e.g., miter saws, planers, drill presses, table saws, lathes, etc.) and other types of electrical devices (e.g., washing machines, compressors, blower units, automotive applications, etc.). In the illustrated construction, the electrical device  100  includes a control housing  104 , a drive unit housing  108  and a driven unit housing  112 . In other constructions, more or fewer housing sections may be utilized (e.g., a single housing formed of two corresponding halves). 
   A first end  116  of the control housing  104  is configured to fit an operator&#39;s hand, and a second end  120  of the control housing  104  houses a majority of an electronics package discussed below in more detail. A trigger  124  is actuated by the operator to operate the electrical device  100  by selectively connecting a power source (not shown) to the SR motor of the electrical device  100 . In the illustrated construction, a power cord  128  electrically connects the electrical device  100  to an AC power source. Other constructions may include a battery pack that acts as a DC power source, a combination of an AC and a DC power source, and/or any other type of power source. 
   The drive unit housing  108  is coupled to the control housing  104  and houses the drive unit (i.e., a SR motor and components associated with the SR motor). The driven unit housing  112  is coupled to the drive unit housing  108  and houses the driven unit. The driven unit of the illustrated electrical device  100  includes a toothed blade  132  which cuts in a reciprocating type motion. The driven unit may be any type of driven unit and shall therefore not be discussed further in detail. 
     FIG. 2  illustrates a schematic view of a representative SR motor  10 . The SR motor  10  includes a rotor  14  mounted for rotation about an axis  18 , and a stator  38  surrounding the rotor  14 . The rotor  14  includes four rotor poles  22 ,  26 ,  30  and  34  evenly spaced about the axis  18 , and extending radially outward from the rotor  14  relative to the axis  18 . The stator  38  has an inner surface  42 , and six stator poles  46 ,  50 ,  54 ,  58 ,  62  and  66  evenly spaced about the inner surface  42 , and extending from the inner surface  42  radially inwardly toward the axis  18 .  FIGS. 3A and 3B  further illustrate one construction of the rotor  14  in more detail. In one construction, the rotor  14  is constructed of a number of laminations  15  as shown in  FIG. 3C .  FIG. 4  illustrates a perspective view of the stator  38  and  FIG. 5A and 5B  further illustrate one construction of the stator  38  in more detail. In one construction, the stator  38  is constructed of a number of laminations  39  as shown in  FIG. 5C . As shown in  FIGS. 4 and 5A , the stator  38  includes a number of apertures  240 , any number of which may extend axially through the stator  38 . In one construction, two diametrically opposite apertures  240   a  and  240   d  include a round shaped cross-section and the remaining four apertures  240   b,    240   c,    240   e  and  240   f  include an oblong shaped cross-section. In other constructions, the positioning of the apertures  240 , the shape of the cross-sections of the apertures  240  and/or the number of apertures  240  may vary. In alternative constructions, other types of positioning features could be utilized. 
   Because the SR motor  10  includes six stator poles and four rotor poles, the SR motor  10  shown in  FIG. 2  is referred to as a 6/4 (six stator pole to four rotor pole ratio) SR motor. While the description refers to the operation of the invention in terms of a 6/4 SR motor, it should be understood that any SR motor having any number of stator poles or rotor poles can be utilized as the drive unit in the electrical device  100 . 
   The SR motor  10  also includes windings or coils  70 ,  74 ,  78 ,  82 ,  86  and  90  on the stator poles  46 ,  50 ,  54 ,  58 ,  62  and  66 , respectively. The windings  70 ,  74 ,  78 ,  82 ,  86  and  90  are made of a conductor of a precise gauge which is wound around the corresponding stator pole  46 ,  50 ,  54 ,  58 ,  62  and  66  a precise number of times or turns. The gauge of the wire and the number of turns vary depending upon the application of the SR motor  10 . The description applies equally to any SR motor using any gauge wire or having any number of turns. 
   The windings  70 ,  74 ,  78 ,  82 ,  86  and  90  on diametrically opposite stator poles  46 ,  50 ,  54 ,  58 ,  62  and  66 , respectively, are connected in series to form three electrically independent phases  1 ,  2  and  3  of the SR motor  10 . In an alternative construction, the windings  70 ,  74 ,  78 ,  82 ,  86  and  90  could be connected in parallel to form the three electrically independent phases  1 ,  2  and  3 . As shown in  FIG. 2 , the windings  70  and  82  on stator poles  46  and  58 , respectively, form pole pairs which together form phase  1 . The windings  74  and  86  on stator poles  50  and  62 , respectively, form pole pairs which together form phase  2 . The windings  78  and  90  on stator poles  54  and  60 , respectively, form pole pairs which together form phase  3 . Because the rotor  14  is made of ferromagnetic material, energizing a particular phase of the SR motor  10  results in the formation of a magnetic attraction between the windings on the stator pole pairs comprising the energized phase and the rotor poles closest to the stator poles of the energized phase. By energizing the phases  1 ,  2  and  3  in a particular manner, the rotational direction and speed of the rotor  14  can be precisely controlled. 
     FIG. 6  illustrates a rotor assembly  130 . The rotor assembly  130  includes a shaft  132  to which the rotor  14  is mounted for rotation about the axis  18 . The shaft  132  rotates in response to rotational forces caused by the rotor  14  in accordance with operation of the SR motor  10  (e.g., in a forward direction and/or in a reverse direction as selectively indicated by the operator of the electrical device  100  (dependent upon the construction of the electrical device  100 )). The shaft  132  is supported for rotational movement about the axis  18  by a first bearing  136  and a second bearing  140 . A fan  144  is also coupled to the shaft  132 . The fan  144  is utilized to dissipate heat from the electrical device  100  as discussed below. As illustrated in  FIG. 7 , a magnet hub  148  may also be mounted to the shaft  132 . The magnet hub  148  includes magnet poles M (not individually shown). In one construction, the magnet hub  148  includes eight magnet poles M (i.e., two magnet poles M per rotor pole). In alternative constructions, the magnet hub  148  may include any number of magnet poles M. The magnet hub  148  may further include any number of magnets that include any number of magnet poles M to provide the overall number of magnet poles M of the magnet hub  148  (e.g., to achieve a total of eight magnet poles M, the magnet hub  148  may include eight magnets with eight magnet poles M, or one magnet with  8  magnet poles M, or two magnets with two magnet poles M each and one magnet with four magnet poles M, etc.). The magnet poles M may be utilized, as discussed below, to determine the speed at which the shaft  132  is rotating, the direction in which the shaft  132  is rotating and the position of the rotor  14  with respect to the stator  38 . 
     FIG. 8  illustrates an exploded view of and  FIG. 9  illustrates a side view of the rotor assembly  130 . A shaft tube  152  may be coupled to the shaft  132  radially inward of the rotor  14 . In one construction, the shaft tube  152  may electrically insulate the rotor  14  from the shaft  132 . 
     FIGS. 10 and 11  illustrate a stator assembly  156  that includes the stator  38 , a rear bell  160 , a terminal board  164  and a front bell  168 .  FIG. 12  illustrates an exploded view of and  FIGS. 13A and 13B  illustrate a side view and an end view of the stator assembly  156 . 
   As shown in  FIGS. 14A ,  14 B,  14 C,  14 D,  14 E, and  14 F, the rear bell  160  includes a first side  244 , a second side  248  and a stepped hub  200  having a magnet pocket  204  and a bearing pocket  208 . The first side  244  includes an opening to the stepped hub  200 . The opening allows the magnet hub  148  and the first bearing  136  to pass through the first side  244  into the stepped hub  200 . As shown in  FIGS. 15 and 16 , when the electrical device  100  is assembled as discussed below, the magnet hub  148  is encapsulated between the stepped hub  200  and the first bearing  136 . The magnet hub  148  is allowed to rotate in the magnet pocket  204  and the first bearing  136  is seated in the bearing pocket  208  such that no contaminants can reach the magnet hub  148  as discussed below in more detail. 
   The first side  244  also includes a first annular region  252  which is positioned radially adjacent and outward of the opening to the stepped hub  200 , and a second annular region  256  which is positioned radially adjacent and outward of the first annular region  252 . The first annular region  252  is substantially planar. The second annular region  256  includes a number of spacer blocks  260  that extend axially away from the plane of the first annular region  252  in a direction opposite the direction of the second side  248 . The second annular region  256  also includes a number of contact apertures  264  that allow contacts of the electronics package to pass through. In one construction, the number of contact apertures  264  corresponds to the number of contacts. 
   In one construction, the second annular region  256  includes six spacer blocks  260   a,    260   b,    260   c,    260   d,    260   e  and  260   f  which are evenly spaced about the circumference of the second annular region  256 . As discussed above, the positioning features utilized may vary. The spacer blocks  260   a  and  260   d  include apertures  266   a  and  266   d,  respectively. In one construction, the apertures  266   a  and  266   d  include a round shaped cross-section corresponding to the round shaped cross-section of apertures  240   a  and  240   d.  In one construction, the apertures  266   a  and  266   d  do not extend to the second side  248 . The spacer blocks  260   c  and  260   f  include pin members  268   c  and  268   f,  respectively. In one construction, the pin members  268   c  and  268   f  include an oblong shaped cross-section corresponding to the oblong shaped cross-section of apertures  240   c  and  240   f.  In one construction, apertures  240   c  and  240   f  are configured to receive pin members  268   c  and  268   f.  In one construction, the spacer blocks  260   b  and  260   e  are axially shorter than the spacer blocks  260   a,    260   c,    260   d  and  260   f.  The spacer blocks  260   b  and  260   e  may be shorter than the spacer blocks  260   a,    260   c,    260   d  and  260   f  by an amount corresponding approximately to the thickness of the terminal plate  164 . The spacer blocks  260   c  and  260   f  include a protrusion (i.e., pin members  268   c  and  268   f ) that results in an overall height profile that is taller than the remaining blocks. However, the pin members  268   c  and  268   f  are utilized such that, when the stator assembly  156  is assembled as discussed below, each spacer block  260   a,    260   b,    260   c,    260   d,    260   e  and  260   f  rests flush against a corresponding surface. 
   The second side  248  of the rear bell  160  includes an exterior stepped annular wall and a closed end of the stepped hub  200 . The second side  248  also includes the contact apertures  264  and apertures  265 . In one construction, the apertures  265  do not extend to the first side  244 . The aperture  265  may be utilized to retain the printed circuit boards to the rear bell  160 . The second side  248  is surrounded by a circumferentially positioned annular wall  272  that extends axially away from the plane of the first annular region  252  in a direction opposite the first side  244 . The annular wall  272  extends axially such that each printed circuit board (“PCB”) of the electronics package is radially enclosed by the annular wall  272  as discussed below. In one construction, the annular wall  272  includes two diametrically opposed flange portions  274 . Each flange portion  274  may includes an aperture  276 . In one construction, the aperture  276  is located on the second side  248  of the flange portion  274  and does not extend through to the first side  244  of the flange portion  274 . The aperture  276  may be utilized to retain the PCBs to the rear bell  160 . 
   As shown in  FIG. 17A , the terminal board  164  includes an aperture  280 . Radially adjacent and outward of the aperture  280  the terminal board  164  includes an annular region  284 . The aperture  280  is preferably sized such that the annular region  284  substantially similar in size to the second annular region  256  of the first side  244  of the rear bell  160 . The annular region  284  includes a number of cutouts  304   a,    304   c,    304   d  and  304   f.  In one construction, the cutouts  304   a  and  304   d  include a recess  305   a  and  305   d,  respectively, having a half-round cross section corresponding to a portion of the round shaped cross-section of the apertures  240   a  and  240   d.  In one construction, the spacing of the cutouts  304   a,    304   c,    304   d  and  304   f  corresponds to the spacing of the spacer blocks  260   a,    260   c,    260   d  and  260   f  (i.e. the spacer blocks that include the apertures  266   a  and  266   d  and the pin members  268   c  and  268   f ). The annular region  284  includes a first side  292  and a second side  296 . The first side  292  is substantially planar. The second side  294  includes a number of pin members  308   b  and  308   e.  In one construction, the pin members  308   b  and  308   e  include an oblong shaped cross-section corresponding to the oblong shaped cross-section of the apertures  240   b  and  240   e.  In one construction, the apertures  240   b  and  240   e  are configured to receive pin members  304   b  and  304   e.  The second side  296  also includes placement locations  300  for placement of terminal blocks  192 . In one construction, the terminal blocks  192  are attached to the terminal board  164  with an adhesive. In another construction, the terminal blocks  192  are integral with the terminal board  164 . The terminal blocks  192  include female connectors  191 . The female connectors  191  are electrically coupled to representative conductors that make up the stator windings of the SR motor  10 . As discussed further below, contacts of the electronics package engage the female connectors  191  thereby releasably electrically coupling the electronics package to the electrically independent phases.  FIGS. 15 and 16  illustrate the releasable engagement. In one construction, the placement locations  300  are spaced such that the spacing of the female connectors  191  in the terminal blocks  192  corresponds to the spacing of the representative contacts that releasably engage the female connectors  191 . In other constructions, the terminal blocks  192  may include male connectors. 
   Referring to  FIGS. 18A ,  18 B,  18 C, and  18 D, the front bell  168  includes a first end  312  and a second end  316 . The first end  312  is configured to be adjacent to the stator  38 . The second end is configured to be adjacent to the gearbox of the driven unit which is housed in the driven unit housing  112 . A circumferentially positioned annular wall  320  connects the first end  312  to the second end  316 . The circumferentially positioned annular wall  320  includes a number of air inlet vents  322 . The air inlet vents  322  may be utilized as part of the heat dissipation techniques discussed below. 
   The first end  312  includes an annular region  324  radially adjacent and outward of an aperture  328 . The aperture  328  is sized such that the annular region  324  is substantially similar in size to the radially outward portion of the stator core. In one construction, the circumferentially positioned annular wall  320  includes a positioner portion  320   p  that extends axially beyond the annular region  324 . The positioner portion  320   p  of the circumferentially positioned annular wall  320  may be utilized to position the front bell  168  with respect to the stator  38 . The positioner portion  320   p  is located radially outward of the stator  38  when utilized to position the front bell  168  with respect to the stator  38 . The annular region  324  includes apertures  329   a  and  329   d.  In one construction, the apertures  329   a  and  329   d  include a round shaped cross-section corresponding to the round shaped cross-section of apertures  240   a  and  240   d.    
   The second end  316  also includes an annular region  332  radially adjacent and outward of an aperture  336 . The aperture  336  is sized such that the annular region  332  is substantially similar in size to the corresponding surface of the driven unit housing  112 . The annular region  332  includes a number of tabs  340 . The tabs  340  include apertures  344  that allow fasteners to pass through which are utilized to position the stator assembly  156  with respect to the drive unit housing  108  and the driven unit housing  112 . 
   Referring to  FIG. 12 , a fan baffle  345  is configured to direct heated air propelled by the fan  144  out of the electrical device  100 . The fan baffle  345  is supported by the annular region  324  and the circumferentially annular wall  320  of the front bell  168 . The fan baffle  345  includes an annular region  348  radially adjacent and outward of an aperture  352 . The aperture  352  is sized such that the annular region  348  is substantially similar in size to the annular region  324 . The annular region  348  includes a triangular shaped cross-section corresponding to the cross-section shape of each blade member of the fan  144 . The fan baffle  345  includes a number of spacer blocks  356  that extend axially towards the annular region  324 . In one construction, the spacer blocks  356  are configured such that the air inlet holes  322  are not blocked by the fan baffle  345 . 
     FIGS. 19A-C  illustrate a schematic diagram of an electronics package that is utilized to control the operation of the SR motor  10  based on the operator&#39;s input using the trigger  124 . The electronics package includes a number of low voltage (e.g., a controller and hall effect devices) and a number of high voltage (i.e., power) components. Generally, power components need to be isolated from low voltage components because electrical noise generated by the power components can disrupt the operation of the low voltage components. A technique for reducing the electrical interference caused by the power components is to separate the power components from the low voltage components by enough space on the PCB on which the power components and the low voltage components are mounted such that the degree of electrical interference experienced by the low voltage components does not disrupt the operation of the low voltage components. As discussed above, space considerations of the illustrated electrical device  100  do not allow for such spacing techniques. Accordingly, in one aspect, the invention provides for the use of two PCBs that are stacked, thereby separating the power components from the low voltage components such that the low voltage components operate as intended. The stacked PCBs are shown in  FIGS. 15 and 16  which illustrate partial sectional views of the electrical device  100 . In other constructions, the components and/or the PCB(s) may be placed alternatively (e.g., some low voltage components placed on a PCB that is perpendicular to a PCB that includes low voltage components and power components), shielding techniques may be utilized to limit the amount of electrical interference received by the low voltage components, and/or other techniques may be utilized to ensure proper operation of the electrical components. 
     FIG. 20  illustrates a perspective view of a first PCB  169  that is utilized primarily for the low voltage components of the electronics package. The first PCB  169  may be screen printed to indicate the location of the components included on the first PCB  169 . The first PCB  169  includes a number of position/speed sensors  193 . In one construction, the position/speed sensors  193  are hall effect devices. The position/speed sensors  193  interact with the magnet hub  148  to determine the speed and direction in which the shaft  132  is rotating and the position of the rotor poles  22 ,  26 ,  30  and  34  with respect to the stator poles  46 ,  50 ,  54 ,  58 ,  62  and  66 , such that the representative phases  1 ,  2  and  3  of the SR motor  10  can be energized at appropriate times to effectively operate the SR motor  10 . Such determinations may be made by the controller in accordance with techniques generally known in the art. In one construction, the first PCB  169  includes an aperture  196 . The aperture  196  corresponds to the size of the stepped hub  200  on the rear bell  160  such that the first PCB  169  can rest against the second side  248  of the rear bell  160 . 
   The aperture  196  of the first PCB  169  may include a number of tabs  212  that correspond to notches  216  in the stepped hub  200  of the rear bell  160 . The position/speed sensors  193  are located on the tabs  212  such that the radial distance between the magnet hub  148  and the position/speed sensors  193  is minimal. As discussed above, the magnet hub  148  includes a number of magnet poles M. As the shaft  132  rotates, the rotor  14  and the magnet hub  148  rotate at the same speed as the shaft  132 . The position/speed sensors  193  sense the magnet poles M as the magnet poles M pass by each position/speed sensor  193 . The position/speed sensors  193  generate a signal representative of what is currently being sensed by the position/speed sensor  193  (e.g., the presence of a north and/or south magnet pole M and the strength of the interaction, or the lack of the presence of a magnet pole M). The controller receives the signal and utilizes the data to determine the speed and direction of the shaft  132  rotation, the position of the rotor  14  with respect to the stator  38  and the energizing pattern of the representative electrically independent phases  1 ,  2  and  3 . In alternative constructions, the method of position/speed sensing could vary (e.g., optical sensing, varied placement of the position/speed sensors  193  (e.g., inboard of the magnet poles M instead of outboard of the magnet poles M such that the signal is obtained from an axial surface of the magnet poles M instead of a radial surface), use of surface mount technology, etc). 
     FIG. 21  illustrates a perspective view of a second PCB  172  that is utilized primarily for the power components of the electronics package.  FIGS. 19A-C  include a section  173  (surrounded by a dashed line). The components in the section  173  generally correspond to the power components, and the components outside of the section  173  generally correspond to the low voltage components. The second PCB  172  may be screen printed in a manner similar to that used on the first PCB  169 . The second PCB  172  includes a large heat sink  176 , a power box  180  (e.g., power transistors and diodes) and storage capacitors  184 . The second PCB  172  further includes a number of connectors (not shown) that electrically connect the second PCB  172  to the first PCB  169 . In one construction, the connectors provide signals (e.g., a power signal and a ground) to the low voltage components mounted on the first PCB  169 . 
   The second PCB  172  also includes a number of contacts  190  (only one contact  190  is illustrated in  FIG. 21 ). As discussed above, each of the contacts  190  is designed to removably electrically couple the electronics package of the electrical device  100  to a representative stator winding  70 ,  74 ,  78 ,  82 ,  86  and  90 . The illustrated contacts  190  are male connectors. The corresponding female connectors  191  are located in the terminal blocks  192 . When the stator assembly  156  is assembled as discussed below, the electronics package is electrically connected to the stator windings  70 ,  74 ,  78 ,  82 ,  86  and  90  and the controller can control the operation of the SR motor  10  in accordance with generally known techniques. 
   In one construction, the second PCB  172  includes one contact  190  for each stator winding, or two contacts for each electrically independent phase. A single conductor is utilized to form the stator windings of the pole pair of stator windings that form an electrically independent phase when the number of contacts  190  equals the number of stator windings. That is, for example, a single conductor is utilized to first form stator winding  74  on stator pole  50  and then stator winding  86  on stator pole  62 . A portion of the single conductor forms an input to the electrically independent phase  2  and another portion of the single conductor forms an output to the electrically independent phase  2 . One contact  190  is electrically coupled to the input, and a second contact  190  is electrically coupled to the output. The controller can then control the operation of that particular phase. 
   In another construction, the second PCB  172  may include twice as many contacts  190  as stator windings, or four contacts for each electrically independent phase. A single conductor is utilized to form a single stator winding when the number of contacts  190  equals twice the number of stator windings. Each stator winding of the pole pair of stator windings that form an electrically independent phase includes an input and an output. A first contact  190  is electrically coupled to the input of a first stator winding, a second contact  190  is electrically coupled to the output of the first stator winding, a third contact  190  is electrically coupled to the input of a second stator winding and a fourth contact  190  is electrically coupled to the output of the second stator winding. The second and third contacts  190  are electrically coupled to one another via the electronics package to form an electrically independent phase. The controller can then control the operation of that particular phase. 
   In an alternative construction of the stator assembly  156 , a terminal plate  164  may be provided on each side of the stator  38  or on the side of the stator  38  opposite to that of the illustrated construction. Techniques in accordance with those discussed above may then be utilized to form the electrically independent phases of the SR motor  10 . 
   It should be understood that the present invention is capable of use with other PCB configurations and that the first PCB  169  and the second PCB  172  are merely shown and described as an example of one such PCB configuration. The illustrated PCB configuration includes two double-sided single-layer PCBs. 
   For example, as is further illustrated in  FIGS. 19A-C , the electrical device  100  may include a third small PCB (not shown) that includes the components in a section  174  (surrounded by a dashed line). The components in section  174  may be utilized to determine a temperature at a location inside the electrical device  100  (e.g., near the electronics mounted on the heat sink  176 ) and may be utilized as part of the heat dissipation techniques discussed below in more detail. In one construction, if the temperature inside the electrical device  100  exceeds a threshold level, the power provided to the electrical device  100  may be automatically limited to ensure the operational parts of the electrical device  100  are not adversely affected by the high temperature. 
   In one construction, the controller of the electronics package is implemented in a programmable device. The controller may operate through the use of a number of inputs. For example, the controller may receive position and speed data from the position/speed sensors  193  from which the motor speed is computed. The controller may also receive input from one or more devices (e.g., the trigger  124 ) which indicate the desired speed of operation as well as the desired direction of rotation (if applicable). Based on the sensed speed and direction and the requested speed and direction, the controller outputs the proper commutation sequence in order to drive the SR motor  10  at the desired speed and direction of rotation. The controller may also receive information regarding the current in the SR motor  10  which can be used to monitor the current for a current overload condition. If such a condition exists, the controller outputs a reduced commutation sequence to limit the current in the windings. The controller may also receive temperature data that is utilized to monitor the temperature of monitored components (e.g. the heat sink  176 , the stator  38 , etc.) for a high temperature condition. If such a condition exists, the controller may output a shutdown command (or alternatively slow the speed of operation) to limit damage to the components of the electrical device  100 . 
   Heat Dissipation 
   Heat generated by the electrical device  100  includes heat generated by the electrical components and heat generated by the stator windings. Heat that is generated needs to be dissipated for efficient operation of the SR motor  10 . Typically, active dissipation techniques are more advantageous than passive dissipation techniques. 
   Power components commonly generate more heat than low voltage components. The heat sink  176  discussed above assists in dissipating heat generated by the power components through passive techniques. The effectiveness of the heat sink  176  can be greatly increased by propelling air across the fins of the heat sink  176  to produce active dissipation. Similarly, components of the SR motor  10  that include windings typically generate much more heat than components that do not include windings. Although the rotor  14  does not include windings, the stator  38  does. The stator  38  therefore adds to the heat generated by the electrical device  100 . This heat must also be dissipated for efficient operation of the electrical device  100 . Again, active dissipation is more effective than passive dissipation. 
   Accordingly, in one aspect, the invention includes a method and apparatus for propelling cooling air through the electrical device  100  such that heat is actively dissipated.  FIGS. 1 and 15  illustrate air intake vents  360  in the control housing  104  of the electrical device  100 . As the shaft  132  rotates, the fan  144  coupled to the shaft  132  rotates and pulls fresh air through the air intake vents  360 . Air entering the air intake vents  360  is cool and can be utilized for the cooling process. Air inside the electrical device  100  is encouraged to continue to travel toward the fan  144 . The air that enters the air intake vents  360  is directed either radially toward the geometry of the heat sink  176  or axially toward the SR motor  10 . 
   The rear bell  160  axially seals the electronics package from the SR motor  10  and, therefore, air that travels across the heat sink  176  is only allowed to travel radially away from the heat sink  176 . As the air travels radially away from the heat sink  176  it encounters an inside surface of the control housing  104  and is directed axially toward the SR motor  10 . 
   Air traveling axially toward the SR motor  10  travels between the circumferentially annular wall  272  and an inside surface of the control unit housing  104 . This air can continue to travel down the inside of the housing between the outside of the stator  38  and an inside surface of the drive unit housing  108  or, alternatively, this air can travel radially inward through gaps between the spacer blocks  260 .  FIGS. 22 and 23  further illustrate the spaces through which the air can travel. The spacer blocks  260  are configured such that air can travel between the spacer blocks  260  and then axially towards the stator windings. Air travelling axially towards the stator windings travels across the stator windings thereby cooling the stator windings. The air then continues to move axially towards the fan  144 . 
   Air traveling between the inside surface of the drive unit housing  108  and the stator  38  cools the outside of the stator  38 . As the air approaches the air inlet vents  322 , the air turns radially inward and travels through the air inlet vents  322  and toward the fan  144 . The heated air is then propelled through the fan and out an air outlet vent  364  ( FIG. 1 ). The air outlet vent  364  vents heated air to the outside of the electrical device  100 . As illustrated in  FIG. 1 , the air outlet vent is at the junction of the drive unit housing  104  and the driven unit housing  108 . Air is allowed to reach the air outlet vent  364  through gaps  368  created between the front bell  168  and the drive unit housing  108 . The front bell  168  is positioned adjacent the driven unit housing  112  at tabs  340 , but as illustrated in  FIG. 23 , the gaps  368  allow the heated air to reach the air outlet vent  364 . When the shaft  132  is rotating (i.e., when the electrical device  100  is operating and therefore generating heat), cool air is continually pulled in through the air intake vents  360  and heated air is continually pushed out of the air outlet vents  364 . In one construction, the fan  144  is a mixed flow fan that allows for axial and radial flow. In alternative constructions, an axial flow fan or a radial flow fan may be utilized. In alternative constructions, the air passages may be altered to allow for an efficient cooling process. 
   Tolerance Stack-Up 
   Manufacturing of a SR motor generally requires that the air gap between the stator  38  and the rotor  14  is small enough that the stator poles  46 ,  50 ,  54 ,  58 ,  62  and  66  and the rotor poles  22 ,  26 ,  30 , and  34  are allowed to interact for efficient operation of the SR motor  10 . Larger air gaps can generally be utilized for efficient operation of the other types of drive units commonly utilized in hand-held power tools. Therefore, the tolerance requirements for an efficient SR motor are generally much fighter than the tolerance requirements for an efficient other type of drive unit (e.g., a universal motor). Despite the potential benefits available through the use of the SR motor  10  as the drive unit for a hand-held power tool, the labor costs associated with producing the SR motor  10  for use in the electrical device  100  are inhibitive when accomplished in accordance with general power tool construction techniques (i.e., with the high tolerance requirements). Accordingly, in one aspect, the invention provides a construction of the electrical device  100  that reduces tolerance “stack-up” as is generally produced during power tool assembly in accordance with general power tool construction techniques. Tolerance stack-up typically does not result in power tool operation problems when the power tool being assembled incorporates a drive unit other than a SR motor because of the use of a larger air gap. 
   General power tool construction techniques include coupling the rotor of the drive unit to the gearbox of the driven unit and coupling the stator of the drive unit to the housing of the power tool. The invention incorporates a reduced tolerance stack-up design though the elimination of a number of the levels of tolerance. For example, the stator assembly  156  is not coupled to any portion of the housing (e.g., the control housing  104 , the drive unit housing  108  and/or the driven unit housing  112 ) for the purpose of aligning the stator assembly  156 . The stator assembly  156  is only positioned inside the housing of the electrical device  100  for the purpose of protecting the internal workings of the electrical device  100 . One end of the rotor assembly  130  is aligned with respect to the stator assembly  156  such that the rotor  14  and the stator  38  are allowed to interact for efficient operation of the SR motor  10 . 
   The rotor assembly  130  is assembled as discussed above. The stator assembly  156  is assembled according to the following process. The stator  38  including the terminal plate  164  is positioned between the front bell  168  and the rear bell  160 . The terminal plate  164  is positioned such that pin members  308   b  and  308   e  are received by apertures  240   b  and  240   e  of the stator  38  and the cutouts  304   a  and  304   d  including the recesses  305   a  and  305 d, respectively, are aligned with the corresponding apertures  240   a  and  240   d  on the stator  38 . The rear bell  160  is positioned on the side of the stator  38  including the terminal plate  164 . The spacer blocks  260  of the rear bell  160  are positioned such that the pin members  268   c  and  268   f  of spacer blocks  260   c  and  260   f  are received by apertures  240   c  and  240   f  of the stator  38  and the apertures  266   a  and  266   d  of spacer blocks  260   a  and  260   d  are aligned with the corresponding apertures  240   a  and  240   d  on the stator  38 . When the terminal plate  164  and the rear bell  160  are aligned in such a manner, the spacer blocks  260   b  and  260   e  rest flush against the terminal plate  164  on the first side  292  of the terminal plate  164  opposite the pin members  308   b  and  308   e,  spacer blocks  260   a,    260   c,    260   d  and  260   f  rest flush against the stator  38  and the second side  296  of the terminal plate  164  rests flush against the stator  38 . In one construction, the spacer blocks  260   b  and  260   e  actually do not rest flush on the terminal plate  164  but float with respect to the terminal plate  164  such that no tolerance stack-up is added due to the terminal plate  164 . The spacer blocks  260   b  and  260   e  may be a fraction of an inch (e.g., 0.004 inches) smaller than the gap they are utilized to fill to achieve this float. Inclusion of the cutouts  304   a,    304   c,    304   d  and  304   f  on the terminal plate  164  and the reduced height profile of spacer blocks  260   b  and  260   e  results in no tolerance stack-up attributable to the terminal plate. The positioner portion  320   p  of the circumferentially annular wall  320  is positioned radially outward of the stator  38 . Such placement positions the annular region  324  adjacent to the stator  38 . The apertures  329   a  and  329   b  are aligned with the corresponding apertures  240   a  and  240   d  on the stator  38 . As illustrated in  FIG. 12 , two bolt members  372   a  and  372   b  are positioned through the apertures  329   a  and  329   b  of the front bell  168 , through the apertures  240   a  and  240   d  of the stator  38 , through the cutouts  304   a  and  304   d  (including the recess  305   a  and  305   d ) of the terminal plate  164  and into the apertures  266   a  and  266   d  of the rear bell  160  wherein the bolt members  372   a  and  372   d  are terminated. As the bolt members  372   a  and  372   d  are fastened, the components of the stator assembly  156  are frictionally engaged with one another. The fan baffle  308  is placed in the front bell  168  resulting in an assembled stator assembly  156  (e.g., the stator assembly illustrated in  FIG. 12 ). In one construction, the bolt members  372   a  and  372   b  are threaded into the apertures  266   a  and  266   d.  In alternative constructions, the stator assembly  156  may be held together with other types of fasteners. 
   After the stator assembly  156  has been assembled, the rotor assembly  130  is coupled to the stator assembly  156  by pressing the end of the shaft  132  including the magnet hub  148  and the first bearing  136  into the stepped hub  200 . In one construction, a tolerance ring is placed radially adjacent and outward of the first bearing  136  in the bearing pocket  208 . The tolerance ring is utilized in one aspect to compensate for any thermal expansion of the rear bell  160 . The other end of the rotor assembly  130  is then coupled to the driven unit housed in the driven unit housing  112 . The combination of the rotor assembly  130  and the stator assembly  156  is positioned in the housing of the electrical device  100 . Tabs  340  and apertures  344  are utilized to position the combination in the drive unit housing  108  and the driven unit housing  112 . 
   The electronics package is then inserted as discussed below. After the electronics package is inserted, the remaining portions of the housing are assembled and the electrical device  100  is readied for use. 
   The method and apparatus for assembling the electrical device  100  reduces tolerance stack-up such that the rotor  14  and the stator  38  interact for efficient operation of the SR motor  10 . Additionally, the method and apparatus for assembling the electrical device  100  are accomplished with labor costs that are competitive in the market. These techniques may be useful in any electrical device  100  that utilizes a SR motor  10 . 
   Self-Contained Electronic Package 
   The electrical device  100  includes an electronics package that is releasably engaged by the remaining components of the stator assembly  156 . Such a construction is advantageous for assembly and future replacement of the electronics package. The characteristics of the SR motor  10  may necessitate replacement of the electronics package at some time. The electronics package may be replaced because of failure of all or a portion thereof of the electronics package and/or to provide enhanced motor operation through use of an improved electronics package (e.g., new software for position/speed sensing). The housing can be removed and the electronics package unengaged from the terminal blocks  192  simply by removing a number of fasteners. A replacement electronics package can then be quickly engaged by the terminal blocks  192  and the housing reassembled. This configuration may also be advantageous in applications of SR motors outside hand-held power tools. 
   The first PCB  169  is coupled to the rear bell  160  through the use of two fasteners (not shown). The fasteners are inserted past two cutouts  376  in the first PCB  169  and into the apertures  265  wherein the fasteners terminate. In one construction, the fasteners are threaded into the apertures  265 . In alternative constructions, the first PCB  169  may be coupled to the rear bell  160  using other methods. The second PCB  172  is then electrically coupled to the first PCB  169  via the connectors that deliver the signals such as power and ground, and via the contacts  190  that engage the female connectors  191  of the terminal blocks  192 . The second PCB  172  is coupled to the rear bell  160  through the use of two fasteners (not shown). The fasteners are inserted through two apertures  378  in the second PCB  172  and into the apertures  276 . In one construction, the apertures  378  have a round shaped cross-section corresponding to the round shaped cross-section of apertures  276 . In one construction, the fasteners are threaded into the apertures  276 . In alternative constructions, the second PCB  172  may be coupled to the rear bell  160  using other methods. Once the first PCB  169  and the second PCB  172  are coupled to the rear bell  160 , the rest of the electrical device  100  can be assembled and readied for operation. 
   Magnet Encapsulation 
   Encapsulation of the magnet hub  148  is advantageous because the magnet hub  148  is therefore not in an environment that may include foreign particles such as metal shavings, and the like, that could become magnetically or otherwise coupled to the magnet poles M of the magnet hub  148 . Foreign particles such as metal shavings and dirt may interfere with the accuracy of determinations of the speed at which the shaft  132  is rotating, the direction in which the shaft  132  is rotating and the position of the rotor  14  with respect to the stator  38 . 
   As discussed above, the magnet hub  148  is encapsulated when the stator assembly  156  and the rotor assembly  130  are combined. When the stator assembly  156  and the rotor assembly  130  are combined, the magnet hub  148  is placed in the magnet pocket  204  and the first bearing  136  is seated in the bearing pocket  208 . The shaft  132  is thereby allowed to rotate about the axis  18  via the first bearing  136  (and the second bearing  140 ) while the outside surface of the first bearing  136  remains frictionally engaged with the bearing pocket  208 . The magnet hub  148  rotates with the shaft  132  in the magnet pocket  204  and is used to determine speed and direction of the SR motor  10  as discussed above. 
   Magnet Alignment 
   The positioning of the magnet poles M with respect to the rotor poles  22 ,  26 ,  30  and  34  which the magnet poles M are intended to represent is important when the interactions between the magnet poles M and the position/speed sensors  193  are used to determine the position of the rotor poles  22 ,  26 ,  30  and  34  with respect to the stator poles  46 ,  50 ,  54 ,  58 ,  62  and  66 . The positioning of the magnet poles M is important for determining position of the rotor  12  with respect to the stator  38  because the process of energizing each of the electrically independent phases  1 ,  2 , and  3  at the appropriate time is needed for efficient operation of the SR motor  10 . Accordingly, since the interactions between the magnet poles M and the position/speed sensors  193  are utilized for, among other things, position sensing, the invention provides an apparatus and a method for aligning the magnet poles M with respect to the rotor poles  22 ,  26 ,  30  and  34  the magnet poles M represent. The positioning of the magnet poles M with respect to the rotor poles  22 ,  26 ,  30  and  34  which the magnet poles M represent is not particularly important when the interactions between the magnet poles M and the position/speed sensors  193  are used only to determine the speed at which and/or the direction in which the shaft  132  is rotating. 
     FIG. 24  illustrates a fixture  220  for aligning the magnet poles M with respect to the rotor poles  22 ,  26 ,  30  and  34  which the magnet poles M represent. The fixture  220  includes a number of magnets  224 . The magnets  224  are preferably spaced in accordance with the spacing of the rotor poles  22 ,  26 ,  30  and  34  (e.g., evenly spaced about the axis  18 ). In alternative constructions of the rotor  14 , the fixture  220  would preferably be correspondingly altered. The magnets  224  are orientated such that the magnet poles M of the magnet hub  148  are attracted to the magnets  224  when the magnet hub  148  is inserted in the fixture  220  (i.e., north poles of magnet hub  148  are attracted to south poles of magnets  224  and south poles of magnet hub  148  are attracted to north poles of magnets  224 ). The fixture  220  includes a number of pole members  228 . The pole members  228  accept two diametrically opposite rotor poles (e.g., rotor poles  22  and  30 ). In one construction, the magnets  224  are circumferentially aligned with respect to the pole members  228  such that the magnet poles M on the magnet hub  148  are aligned with respect to the magnets  224  such that the position of each magnet poles M is known with respect to a leading edge or a trailing edge of the rotor pole which the corresponding magnet pole M represents. When the position of the magnet pole M being sensed is correlated to a position on the rotor pole which the magnet pole M represents, the controller can determine the optimum time to energize each of the electrically independent phases  1 ,  2  and  3 . 
   To align the magnet poles M of the magnet hub  148  with respect to the rotor poles  22 ,  26 ,  30  and  34  the magnet poles M represent, the magnet hub  148  is first placed in a recess  232  of the fixture  220 . In one construction, the magnet hub  148  is placed in the recess  232  such that the magnet portion of the magnet hub  148  (see  FIG. 10 ) is facing downward in the recess  232 . The recess  232  includes a spring biased member  236 . The spring biased member  236  supports the magnet hub  148  such that the magnet poles M align with respect to the magnets  224  thereby rotating the magnet hub  148 . In one construction, all of the magnet poles M are identically sized and the magnet hub  148  can be initially positioned in any orientation as discussed above. Once the magnet poles M of the magnet hub  148  have reached equilibrium, a partially assembled rotor assembly  130  (e.g., the rotor assembly  130  illustrated in  FIG. 6 ) is inserted into the fixture  220  such that the first bearing  136  side of the shaft  132  is facing downward in the fixture  220 . The end of the shaft  132  is inserted into the aperture  232  of the magnet hub  148  and the partially assembled rotor assembly  130  is forcibly pushed downward in the fixture  220 . The spring biased member  236  retracts in response to the force and the magnet hub  148  is coupled to the end of the shaft  132 . The rotor assembly  130  (e.g., the rotor assembly  130  illustrated in  FIG. 7 ) can then be used to assemble the electrical device  100  as discussed above. 
   Alternate Constructions 
     FIGS. 25 ,  26 ,  27 ,  28 , and  29  illustrate an alternate construction of a portion of the electrical device  100 . The alternate construction includes an electronics module (not shown) that is coupled to the electrical device  100  by at least one lead or connector. 
     FIGS. 25 and 26  illustrate a stator assembly  400  that is similar to the stator assembly  156  except that the stator assembly  400  does not include the terminal board  164  or the rear bell  160 . The stator assembly  400  instead includes a rear structure  404  that supports the bearing  136  of the rotor assembly  130 . The magnet hub  148  is allowed to rotate in a fashion similar to that of the construction discussed above. 
     FIGS. 27 ,  28 , and  29  illustrate partial assemblies of the alternate construction. A PCB  408  is coupled to the rear structure  404 . The PCB  408  includes position/speed sensors that interact with the magnet poles of the magnet hub  148  as discussed above. The rear structure  404  includes a number of apertures  412   a - f  that correspond to the apertures  240   a - f.    
     FIGS. 30 ,  31 ,  32 ,  33 ,  34 ,  35 ,  36 ,  37 , and  38  illustrate an alternative construction of an electrical device  1000 . In the illustrated alternative construction, the electrical device  1000  is a circular saw. The electrical device  100  and the electrical device  1000  are substantially identical with respect to the disclosed aspects. Common components of the electrical device  100  are indicated by the same reference numerals in the one-thousand series. Although the electrical device  100  and the electrical device  1000  have an obviously different appearance, the integration of the SR motor of the electrical device  1000  and the electronics package utilized to operate the SR motor of the electrical device  1000  is almost identical to the integration of SR motor  10  and the electronics package utilized to operate the SR motor  10 . The component parts of the rotor assembly  1130  and the stator assembly  1156  may vary in shape and size, but the function is similar to that discussed above with respect to the rotor assembly  130  and the stator assembly  156 . 
     FIG. 30  illustrates a perspective view of the electrical device  1000 .  FIGS. 31 and 32  illustrate perspective views of the rotor assembly  1130 .  FIGS. 33 and 34  illustrate perspective views of the stator assembly  1156 .  FIG. 35  illustrates a partial sectional view of the electrical device  1000  illustrated in  FIG. 30 .  FIG. 36  illustrates a perspective view of a second PCB  1172 .  FIGS. 37 and 38  illustrate perspective views of the electrical device  1000  with a portion of the housing removed. 
   Thus, the invention provides, among other things, an electrical device that includes a SR motor. One or more independent features and independent advantages of the invention are set forth in the following claims: