CA2106052C - Cooling system - Google Patents
Cooling systemInfo
- Publication number
- CA2106052C CA2106052C CA002106052A CA2106052A CA2106052C CA 2106052 C CA2106052 C CA 2106052C CA 002106052 A CA002106052 A CA 002106052A CA 2106052 A CA2106052 A CA 2106052A CA 2106052 C CA2106052 C CA 2106052C
- Authority
- CA
- Canada
- Prior art keywords
- motor
- electric motor
- fan
- stator
- operatively
- 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 - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K9/00—Arrangements for cooling or ventilating
- H02K9/02—Arrangements for cooling or ventilating by ambient air flowing through the machine
- H02K9/04—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium
- H02K9/06—Arrangements for cooling or ventilating by ambient air flowing through the machine having means for generating a flow of cooling medium with fans or impellers driven by the machine shaft
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Motor Or Generator Cooling System (AREA)
Abstract
A cooling system for an electric motor is designed to be mounted on an end of the electric motor. The cooling system includes an independently powered electric motor which is designed as an inverted induction motor, in which a ring-shaped rotor rotates about an annular stator. The annular shape of the stator provides a cavity into (and/or through) which the shaft of the electric motor can protrude. The ring shaped rotor is supported and maintained in place about the stator by a bearing-mounted fan.
Description
~1~6~5~
The present invention relates to a cooling system for an electric motor, and in particular to a compact fan unit designed to be mounted on an end of an electric motor for delivering a flow of air across the housing of the electric motor.
Electric motors are often cooled by passing air over cooling fins located on the motor housing. To cause such a flow of air, it is common to attach a cooling fan directly to the motor's shaft at the non-drive end of the motor. The fan is thus driven by the motor itself. A shroud is generally placed over the fan such that air drawn into the shroud is directed over the cooling fins of the motor.
However, in the case of variable speed and/or low speed motors, shaft mounted fans of the above-mentioned type often provide inadequate cooling, particularly at low operating speeds. For example, in many cases (such as, for example, in a crane or elevator), a motor will be required to develop its maximum rated torque at low, or possibly even zero speed. Under these conditions, the flow of air produced by a fan directly coupled to the motor shaft will be essentially zero, so the fan will not produce any cooling effect.
However, since the torque generated by the motor is dependent on the current, heat generated in the motor, due to I2R
losses, can be very large, even if the motor rotation speed is very low. Other electric motors for which shaft mounted fans are inadequate include motors with short time rated overloading, such as are associated with crane duty, and direct current motors having continuously energized field poles.
In order to address this deficiency, it is known to provide a separate motor-driven fan, operating independently of the motor to be cooled, to provide a flow of cooling air.
For example, Canadian Patent No. 2,066,957 (Bauer et al) discloses an electrically powered food processor in which a variable speed motor is cooled by an independently driven blower unit. Referring to Figure 1 of this patent, air is a~ 060 5 2 ~
, drawn by the independent blower through the variable speed motor and a duct system, and is exhausted out of the food processor housing. The blower is composed of a radial impeller driven by a conventional DC motor. This type of arrangement is suitable for small motors, such as a food processor, but is unacceptable for large motor installations.
This is because the space provided in equipment and machine rooms in which motors of this type are typically installed, is frequently insufficient for bulky duct systems.
Canadian Patent No. 2,012,447 (Wolcott) discloses a cooling system for an asynchronous motor. The cooling system comprises two conventional centrifugal blower units mounted so as to force cooling air into the housing of the motor. The interior of the motor housing is provided with baffles and the like so as to conduct the flow of cooling air around the stator coils in such a manner as to ensure even and effective cooling thereof. In addition, the stator is provided with channels which permit a flow of cooling air therethrough, so as to increase the cooling of the stator.
While this arrangement eliminates the bulky duct system of Canadian Patent No. 2,066,957 (Bauer et al), it requires that the motor housing and stator be specially fabricated to provide the necessary baffles and cooling channels, which substantially increases the overall size of the motor.
Furthermore, the special motor housing and stator design means that the arrangement taught by Canadian Patent No. 2,012,447 (Wolcott) cannot be applied as a retrofit to existing electric motors.
United States Patent No. 4,429,242 (Layh) teaches a system for converting a constant speed motor into a variable speed motor. This arrangement consists of a tachometric generator coupled directly to the non-drive end of the motor's shaft. An independently powered blower unit is also provided to supply a flow of cooling air to the motor. The tachometric generator, and the blower unit are mounted substantially co-axially with the motor shaft within a housing which is designed to be fitted on the end of the motor's housing.
While this system is designed to be applied as a retrofit, it will be seen from figure 1 of this references that the considerable size of the blower unit (the fan and its drive motor) means that installation of this system (even without the tacheometric generator) significantly increases the overall length of the motor.
It is therefore an object of the present invention to provide a cooling system for electric motors which can be mounted as a retrofit onto existing motors, while minimizing any increase in the overall size of the motor as a result of such retrofit installation.
Thus according to an aspect of the present invention, there is provided an apparatus for cooling an electric motor having a shaft, comprising: mounting means capable of operatively securing said apparatus to an end of said electric motor; motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means when said apparatus is operatively installed on said electric motor; and fan means drivably coupled to said motor means.
A further aspect of the invention provides an electric motor having an independently driven cooling system, said cooling system comprising: mounting means capable operatively securing said apparatus to an end of said electric motor; motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means; and fan means drivably coupled to said motor means.
In a preferred embodiment of the present invention, the motor means is formed as an inverted squirrel cage motor, in which a ring-shaped rotor surrounds an annular stator.
This arrangement allows the annular stator to provide a recess into which an end of the motor shaft can protrude. In addition the recess formed by the annular stator is capable of accommodating conventional sensors (such as a tachometer ~l o~a5~
sensor) which may be mounted in relation to the non-drive end of the motor shaft. A particular advantage of this arrangement lies in the fact that the stator (by virtue of its being stationary with respect to the motor housing) can also serve to protect the sensor (and its associated wires) from the rotating parts of the cooling system.
In a preferred embodiment of the invention, the rotor and fan are arranged so as to be coaxial with the shaft of an electric motor to be cooled. Such an arrangement lends itself to a compact design, and facilitates the creation of a flow of air which is distributed evenly over the electric motor.
The fan is preferably surrounded by a suitable shroud which directs the flow of air created by the fan over the housing of the electric motor.
In an embodiment of the invention, the mounting means includes base plate means designed to attach to a flange having standard dimensions. Many electric motors are designed to employ a standard flange, such as a type C- or D- flange as specified by the National Electrical Manufacturers Associationff (NEMA) mounted on its drive end to facilitate driving connection of the motor to pumps and the like.
However, in many cases, it is also possible to mount a flange of this type on the non-drive end of the motor. Thus in this embodiment, the non-drive end of the motor is fitted with a standard flange, and the base-plate means is designed to be mounted on the flange.
The cooling system of the present invention is particularly suitable for use in cooling variable speed induction motors. However, this field of application is in no way limitative of the present invention. Other applications include motors with short time rated overloading (such as those used in crane duty), in which case the cooling system would operate continually, and D.C. motors having continuously energized field poles. The cooling system of the present invention can also advantageously be employed in 2~û6~2 situations where provision of continuous cooling would permit a smaller motor to be utilized.
Embodiments of the invention will now be described by way of example, with reference to the accompanying s drawings, in which:
Figure 1 is a cross-sectional side view of a cooling system according to an embodiment of the present invention;
Figure 2 is a cross-sectional side view of a cooling system according to a second embodiment of the present invention; and Figure 3 is a simplified schematic illustration of a control system for controlling a motor and a cooling system according to an embodiment of the present invention.
Note that throughout the Figures, like elements are identified by like reference numerals.
Referring to Figure 1, a cooling system 1 of the invention is illustrated operatively mounted on the non-drive end of a electric motor 2. The electric motor 2 is shown fitted with a face flange conforming to NEMA C standards.
The NEMA C face standard dimensions dictate bolt spacings, shaft sizes, etc. and thus provide a standard mechanical interface for the installation of pumps, hydraulic power units, blowers, etc. to motors of various ratings produced by various manufacturers. It will be noted, however, that other standards are available such as, inter alia, those specified by the British Standards Institute~ (BSI), British Standards Specifications~ (BSS), German Institute for StAnA~rdization~ (DIN), and the Association of Electrical Engineers of Germany~ (VDE), to which the cooling system 1 can be readily adapted.
The cooling system 1 includes a baseplate 3 which is designed to facilitate connection onto an end (normally the non-drive end) of the electric motor 2. In cases where the electric motor 2 is provided with a standard flange (such as a NEMA C face flange) the base plate 3 would be fabricated according to the particular st~n~rd, so as to facilitate easy ~l06a~2 mounting onto the standard flange. In cases where a standard flange is not provided, the base plate 3 would be fabricated to be mounted on the motor 2 using bolt holes (not shown) normally provided on the housing of the motor 2 to permit installation of auxiliary equipment, such as a conventional cooling fan driven by the shaft 2a of the motor 2.
The cooling system 1 comprises a motor unit 4 mounted on the base plate 3, which powers a fan 5. The motor unit 4 is provided with an annular configuration, which leaves an open cavity 4a in the interior of the motor unit 4. In the illustrated embodiment, the stator 6 and field windings 7 of the motor unit 4 are mounted directly onto the base plate 3.
The rotor 8 of the motor unit 4 surrounds the stator 6, so that the resulting configuration of the motor unit 4 is inverted in relation to a conventional electric motor.
The fan 5 is comprised of a fan disc 9 attached at its periphery to the rotor 8. The fan disc 9 can be either flat, or bowl-shaped as illustrated. Fan blades 10 mounted on the outer face of the fan disc 9 may be of any suitable design. The fan 5 and rotor 8 are rotatably supported by a fan/rotor support shaft 11 through a bearing assembly 12. The fan/rotor support shaft 11 is in turn supported by a support bracket 13 mounted on the base plate 3. The bearing assembly 12 and support bracket 13 may have any suitable design provided that the resulting structure is sufficiently rigid to ensure maintenance of adequate air gap tolerances between the rotor 8 and the stator 6 during operation of the cooling system 1. In addition, the support bracket 13 should not unduly interfere with the operation of the fan 5 and the flow of air through the cooling system.
An essentially conventional shroud 14 conveniently surrounds the fan 5 and motor unit 4, providing a shield for the fan to protect personnel from injury. In addition, the shroud 14 permits air to enter the fan 5 in a directional manner, and facilitates the production of a concentrated 21G~S2 stream of air directed across the surface of the motor housing, thereby providing the desired cooling effect.
In the illustrated embodiment, the motor unit 4 is constructed as an inverted induction motor. In a conventional induction motor (sometimes referred to as a repulsion induction motor) the stator consists of steel laminations and associated field windings located within a steel shell disposed about a rotating member (the rotor). The rotor conventionally consists of steel laminations having slots or holes. During assembly, the steel laminations are stacked so that the slots or holes are aligned, and a molten conductive metal (typically aluminum) is injected into the slots or holes. Simultaneously a conductive metal ring (composed of the same material as that injected into the slots) is formed at each end of the rotor to join the cast slot bars together, thereby creating the rotor windings in the form of an electrically conductive metal cage, embedded within the laminated steel assembly forming the rotor. (Hence the term "squirrel cage motor").
In the illustrated embodiment of the present invention, this conventional construction has been inverted, so that the stator 6 (and associated stator windings 7) is mounted on the base place, and the rotor (and its embedded "squirrel cage" rotor winding) is disposed about the stator.
This configuration has the particular advantage that a cavity 4a is provided within the interior of the motor unit 4, and this cavity is surrounded by stationary components (the stator 6). As a result, sensor devices (for example magnetic detectors, encoders, or other devices capable of sensing differential rotary motion) and the like can be mounted on the end of the shaft 2a of the motor 2 (for example, to monitor and control speed, positioning, acceleration rates etc. of the motor 2), and wires associated therewith can be safely lead thereto without having to be routed past rapidly moving components. This simplifies the installation of such sensor equipment, and contributes to reducing maintenance problems.
21~6~2 Figure 3 is a simplified schematic illustration of a controller system for a motor 2 and a cooling system 1 according to the present invention, in which the motor 2 and the cooling system 1 are controlled by respective control units 16 and 17 through respective control lines 16a and 17a.
It will be noted that, in the schematic illustration, the cooling system controller 16 and the motor controller 17 are illustrated as being separate units. It will be readily apparent, however, that these controllers can equally be suitably provided as separate components or as a single integrated unit. During operation of the cooling system 1, the stator windings 7 are powered by an alternating current supplied by the cooling system controller 16. Magnetically induced forces between the stator windings 7 and the rotor windings 8a cause rotation of the rotor 8 and fan 5. The alternating current source supplying the stator windings 7 is preferably isolated from the power source driving the motor 2, so that the cooling system 1 operates independently of the operating speed of the motor 2. In general, the cooling system controller 16 and the motor controller 17 are independent so that, for example, a variable frequency voltage can conveniently be used to drive the motor 2 (for variable speed operation), while a fixed frequency voltage would power the cooling system 1 to provide constant fan speed.
Normally, the cooling system controller 16 powers the cooling system 1 at all times when the motor 2 is energised by the motor controller 17, regardless of the rotation speed of the motor shaft 2a. However, as an optional feature, one or more suitable sensors 18 (such as, for example, conventional thermocouples or other types of temperature sensors) can be mounted in the motor 2 so as to detect the temperature thereof. The cooling system controller 16 can then use the output of the sensor(s) 18 to energise the cooling system 1 as required to maintain the temperature of the motor 2 below a desired maximum temperature.
2 ~
It will be apparent from the foregoing that various modifications, variations and adaptations may be made to the above described and illustrated preferred embodiment of the present invention without departing from the scope of the invention. For example, Figure 2 illustrates an embodiment of the present invention in which the support shaft 11 and support bracket 13 have been replaced by a hollow cylindrical support structure 15 attached directly to the base plate 3.
The support structure lS is designed to provide a substantially rigid foundation for both the stator 6, and the fan unit 5. As with the embodiment illustrated in Figure 1, the support structure 15 provides a hollow cavity 15a into which the end of the shaft 2a can protrude. However, in the case this second embodiment, the open end of the support structure 15 provides simplified access to the end of the shaft 2a. This facilitates easy mounting and service of any sensor equipment which may be mounted thereon on the shaft 2a.
In addition, it will be apparent that by suitably modifying the shroud 14 the cooling system 1 can be readily mounted on the drive end of the motor 2, with the shaft 2a protruding completely through the cooling system 1 and being drivably coupled to another device (for example through a universal coupling, not shown).
The present invention relates to a cooling system for an electric motor, and in particular to a compact fan unit designed to be mounted on an end of an electric motor for delivering a flow of air across the housing of the electric motor.
Electric motors are often cooled by passing air over cooling fins located on the motor housing. To cause such a flow of air, it is common to attach a cooling fan directly to the motor's shaft at the non-drive end of the motor. The fan is thus driven by the motor itself. A shroud is generally placed over the fan such that air drawn into the shroud is directed over the cooling fins of the motor.
However, in the case of variable speed and/or low speed motors, shaft mounted fans of the above-mentioned type often provide inadequate cooling, particularly at low operating speeds. For example, in many cases (such as, for example, in a crane or elevator), a motor will be required to develop its maximum rated torque at low, or possibly even zero speed. Under these conditions, the flow of air produced by a fan directly coupled to the motor shaft will be essentially zero, so the fan will not produce any cooling effect.
However, since the torque generated by the motor is dependent on the current, heat generated in the motor, due to I2R
losses, can be very large, even if the motor rotation speed is very low. Other electric motors for which shaft mounted fans are inadequate include motors with short time rated overloading, such as are associated with crane duty, and direct current motors having continuously energized field poles.
In order to address this deficiency, it is known to provide a separate motor-driven fan, operating independently of the motor to be cooled, to provide a flow of cooling air.
For example, Canadian Patent No. 2,066,957 (Bauer et al) discloses an electrically powered food processor in which a variable speed motor is cooled by an independently driven blower unit. Referring to Figure 1 of this patent, air is a~ 060 5 2 ~
, drawn by the independent blower through the variable speed motor and a duct system, and is exhausted out of the food processor housing. The blower is composed of a radial impeller driven by a conventional DC motor. This type of arrangement is suitable for small motors, such as a food processor, but is unacceptable for large motor installations.
This is because the space provided in equipment and machine rooms in which motors of this type are typically installed, is frequently insufficient for bulky duct systems.
Canadian Patent No. 2,012,447 (Wolcott) discloses a cooling system for an asynchronous motor. The cooling system comprises two conventional centrifugal blower units mounted so as to force cooling air into the housing of the motor. The interior of the motor housing is provided with baffles and the like so as to conduct the flow of cooling air around the stator coils in such a manner as to ensure even and effective cooling thereof. In addition, the stator is provided with channels which permit a flow of cooling air therethrough, so as to increase the cooling of the stator.
While this arrangement eliminates the bulky duct system of Canadian Patent No. 2,066,957 (Bauer et al), it requires that the motor housing and stator be specially fabricated to provide the necessary baffles and cooling channels, which substantially increases the overall size of the motor.
Furthermore, the special motor housing and stator design means that the arrangement taught by Canadian Patent No. 2,012,447 (Wolcott) cannot be applied as a retrofit to existing electric motors.
United States Patent No. 4,429,242 (Layh) teaches a system for converting a constant speed motor into a variable speed motor. This arrangement consists of a tachometric generator coupled directly to the non-drive end of the motor's shaft. An independently powered blower unit is also provided to supply a flow of cooling air to the motor. The tachometric generator, and the blower unit are mounted substantially co-axially with the motor shaft within a housing which is designed to be fitted on the end of the motor's housing.
While this system is designed to be applied as a retrofit, it will be seen from figure 1 of this references that the considerable size of the blower unit (the fan and its drive motor) means that installation of this system (even without the tacheometric generator) significantly increases the overall length of the motor.
It is therefore an object of the present invention to provide a cooling system for electric motors which can be mounted as a retrofit onto existing motors, while minimizing any increase in the overall size of the motor as a result of such retrofit installation.
Thus according to an aspect of the present invention, there is provided an apparatus for cooling an electric motor having a shaft, comprising: mounting means capable of operatively securing said apparatus to an end of said electric motor; motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means when said apparatus is operatively installed on said electric motor; and fan means drivably coupled to said motor means.
A further aspect of the invention provides an electric motor having an independently driven cooling system, said cooling system comprising: mounting means capable operatively securing said apparatus to an end of said electric motor; motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means; and fan means drivably coupled to said motor means.
In a preferred embodiment of the present invention, the motor means is formed as an inverted squirrel cage motor, in which a ring-shaped rotor surrounds an annular stator.
This arrangement allows the annular stator to provide a recess into which an end of the motor shaft can protrude. In addition the recess formed by the annular stator is capable of accommodating conventional sensors (such as a tachometer ~l o~a5~
sensor) which may be mounted in relation to the non-drive end of the motor shaft. A particular advantage of this arrangement lies in the fact that the stator (by virtue of its being stationary with respect to the motor housing) can also serve to protect the sensor (and its associated wires) from the rotating parts of the cooling system.
In a preferred embodiment of the invention, the rotor and fan are arranged so as to be coaxial with the shaft of an electric motor to be cooled. Such an arrangement lends itself to a compact design, and facilitates the creation of a flow of air which is distributed evenly over the electric motor.
The fan is preferably surrounded by a suitable shroud which directs the flow of air created by the fan over the housing of the electric motor.
In an embodiment of the invention, the mounting means includes base plate means designed to attach to a flange having standard dimensions. Many electric motors are designed to employ a standard flange, such as a type C- or D- flange as specified by the National Electrical Manufacturers Associationff (NEMA) mounted on its drive end to facilitate driving connection of the motor to pumps and the like.
However, in many cases, it is also possible to mount a flange of this type on the non-drive end of the motor. Thus in this embodiment, the non-drive end of the motor is fitted with a standard flange, and the base-plate means is designed to be mounted on the flange.
The cooling system of the present invention is particularly suitable for use in cooling variable speed induction motors. However, this field of application is in no way limitative of the present invention. Other applications include motors with short time rated overloading (such as those used in crane duty), in which case the cooling system would operate continually, and D.C. motors having continuously energized field poles. The cooling system of the present invention can also advantageously be employed in 2~û6~2 situations where provision of continuous cooling would permit a smaller motor to be utilized.
Embodiments of the invention will now be described by way of example, with reference to the accompanying s drawings, in which:
Figure 1 is a cross-sectional side view of a cooling system according to an embodiment of the present invention;
Figure 2 is a cross-sectional side view of a cooling system according to a second embodiment of the present invention; and Figure 3 is a simplified schematic illustration of a control system for controlling a motor and a cooling system according to an embodiment of the present invention.
Note that throughout the Figures, like elements are identified by like reference numerals.
Referring to Figure 1, a cooling system 1 of the invention is illustrated operatively mounted on the non-drive end of a electric motor 2. The electric motor 2 is shown fitted with a face flange conforming to NEMA C standards.
The NEMA C face standard dimensions dictate bolt spacings, shaft sizes, etc. and thus provide a standard mechanical interface for the installation of pumps, hydraulic power units, blowers, etc. to motors of various ratings produced by various manufacturers. It will be noted, however, that other standards are available such as, inter alia, those specified by the British Standards Institute~ (BSI), British Standards Specifications~ (BSS), German Institute for StAnA~rdization~ (DIN), and the Association of Electrical Engineers of Germany~ (VDE), to which the cooling system 1 can be readily adapted.
The cooling system 1 includes a baseplate 3 which is designed to facilitate connection onto an end (normally the non-drive end) of the electric motor 2. In cases where the electric motor 2 is provided with a standard flange (such as a NEMA C face flange) the base plate 3 would be fabricated according to the particular st~n~rd, so as to facilitate easy ~l06a~2 mounting onto the standard flange. In cases where a standard flange is not provided, the base plate 3 would be fabricated to be mounted on the motor 2 using bolt holes (not shown) normally provided on the housing of the motor 2 to permit installation of auxiliary equipment, such as a conventional cooling fan driven by the shaft 2a of the motor 2.
The cooling system 1 comprises a motor unit 4 mounted on the base plate 3, which powers a fan 5. The motor unit 4 is provided with an annular configuration, which leaves an open cavity 4a in the interior of the motor unit 4. In the illustrated embodiment, the stator 6 and field windings 7 of the motor unit 4 are mounted directly onto the base plate 3.
The rotor 8 of the motor unit 4 surrounds the stator 6, so that the resulting configuration of the motor unit 4 is inverted in relation to a conventional electric motor.
The fan 5 is comprised of a fan disc 9 attached at its periphery to the rotor 8. The fan disc 9 can be either flat, or bowl-shaped as illustrated. Fan blades 10 mounted on the outer face of the fan disc 9 may be of any suitable design. The fan 5 and rotor 8 are rotatably supported by a fan/rotor support shaft 11 through a bearing assembly 12. The fan/rotor support shaft 11 is in turn supported by a support bracket 13 mounted on the base plate 3. The bearing assembly 12 and support bracket 13 may have any suitable design provided that the resulting structure is sufficiently rigid to ensure maintenance of adequate air gap tolerances between the rotor 8 and the stator 6 during operation of the cooling system 1. In addition, the support bracket 13 should not unduly interfere with the operation of the fan 5 and the flow of air through the cooling system.
An essentially conventional shroud 14 conveniently surrounds the fan 5 and motor unit 4, providing a shield for the fan to protect personnel from injury. In addition, the shroud 14 permits air to enter the fan 5 in a directional manner, and facilitates the production of a concentrated 21G~S2 stream of air directed across the surface of the motor housing, thereby providing the desired cooling effect.
In the illustrated embodiment, the motor unit 4 is constructed as an inverted induction motor. In a conventional induction motor (sometimes referred to as a repulsion induction motor) the stator consists of steel laminations and associated field windings located within a steel shell disposed about a rotating member (the rotor). The rotor conventionally consists of steel laminations having slots or holes. During assembly, the steel laminations are stacked so that the slots or holes are aligned, and a molten conductive metal (typically aluminum) is injected into the slots or holes. Simultaneously a conductive metal ring (composed of the same material as that injected into the slots) is formed at each end of the rotor to join the cast slot bars together, thereby creating the rotor windings in the form of an electrically conductive metal cage, embedded within the laminated steel assembly forming the rotor. (Hence the term "squirrel cage motor").
In the illustrated embodiment of the present invention, this conventional construction has been inverted, so that the stator 6 (and associated stator windings 7) is mounted on the base place, and the rotor (and its embedded "squirrel cage" rotor winding) is disposed about the stator.
This configuration has the particular advantage that a cavity 4a is provided within the interior of the motor unit 4, and this cavity is surrounded by stationary components (the stator 6). As a result, sensor devices (for example magnetic detectors, encoders, or other devices capable of sensing differential rotary motion) and the like can be mounted on the end of the shaft 2a of the motor 2 (for example, to monitor and control speed, positioning, acceleration rates etc. of the motor 2), and wires associated therewith can be safely lead thereto without having to be routed past rapidly moving components. This simplifies the installation of such sensor equipment, and contributes to reducing maintenance problems.
21~6~2 Figure 3 is a simplified schematic illustration of a controller system for a motor 2 and a cooling system 1 according to the present invention, in which the motor 2 and the cooling system 1 are controlled by respective control units 16 and 17 through respective control lines 16a and 17a.
It will be noted that, in the schematic illustration, the cooling system controller 16 and the motor controller 17 are illustrated as being separate units. It will be readily apparent, however, that these controllers can equally be suitably provided as separate components or as a single integrated unit. During operation of the cooling system 1, the stator windings 7 are powered by an alternating current supplied by the cooling system controller 16. Magnetically induced forces between the stator windings 7 and the rotor windings 8a cause rotation of the rotor 8 and fan 5. The alternating current source supplying the stator windings 7 is preferably isolated from the power source driving the motor 2, so that the cooling system 1 operates independently of the operating speed of the motor 2. In general, the cooling system controller 16 and the motor controller 17 are independent so that, for example, a variable frequency voltage can conveniently be used to drive the motor 2 (for variable speed operation), while a fixed frequency voltage would power the cooling system 1 to provide constant fan speed.
Normally, the cooling system controller 16 powers the cooling system 1 at all times when the motor 2 is energised by the motor controller 17, regardless of the rotation speed of the motor shaft 2a. However, as an optional feature, one or more suitable sensors 18 (such as, for example, conventional thermocouples or other types of temperature sensors) can be mounted in the motor 2 so as to detect the temperature thereof. The cooling system controller 16 can then use the output of the sensor(s) 18 to energise the cooling system 1 as required to maintain the temperature of the motor 2 below a desired maximum temperature.
2 ~
It will be apparent from the foregoing that various modifications, variations and adaptations may be made to the above described and illustrated preferred embodiment of the present invention without departing from the scope of the invention. For example, Figure 2 illustrates an embodiment of the present invention in which the support shaft 11 and support bracket 13 have been replaced by a hollow cylindrical support structure 15 attached directly to the base plate 3.
The support structure lS is designed to provide a substantially rigid foundation for both the stator 6, and the fan unit 5. As with the embodiment illustrated in Figure 1, the support structure 15 provides a hollow cavity 15a into which the end of the shaft 2a can protrude. However, in the case this second embodiment, the open end of the support structure 15 provides simplified access to the end of the shaft 2a. This facilitates easy mounting and service of any sensor equipment which may be mounted thereon on the shaft 2a.
In addition, it will be apparent that by suitably modifying the shroud 14 the cooling system 1 can be readily mounted on the drive end of the motor 2, with the shaft 2a protruding completely through the cooling system 1 and being drivably coupled to another device (for example through a universal coupling, not shown).
Claims (19)
1. An apparatus for cooling an electric motor having a shaft, comprising:
mounting means capable of operatively securing said apparatus to an end of said electric motor;
motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means when said apparatus is operatively installed on said electric motor; and fan means drivably coupled to said motor means.
mounting means capable of operatively securing said apparatus to an end of said electric motor;
motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means when said apparatus is operatively installed on said electric motor; and fan means drivably coupled to said motor means.
2. An apparatus as claimed in claim 1, wherein said motor means comprises:
stator means substantially fixedly mounted on said mounting means, said stator means having an annular configuration such that an end of the shaft of said electric motor can operatively protrude into the interior of said stator means when said apparatus is installed on said electric motor; and annular rotor means operatively disposed about said stator means, said rotor means being drivably coupled to said fan means.
stator means substantially fixedly mounted on said mounting means, said stator means having an annular configuration such that an end of the shaft of said electric motor can operatively protrude into the interior of said stator means when said apparatus is installed on said electric motor; and annular rotor means operatively disposed about said stator means, said rotor means being drivably coupled to said fan means.
3. An apparatus as claimed in claim 1, wherein said fan means includes a fan disc rotatably supported in spaced relation to said motor means, a peripheral edge of said fan disc being substantially fixedly attached to said rotor means.
4. An apparatus as claimed in claim 3, wherein said rotor means is operatively supported about said stator means by said fan disc.
5. An apparatus as claimed in claim 3 or 4, wherein said fan disc has an annular configuration.
6. An apparatus as claimed in claim 1, 2, 3 or 4, further comprising support means depending from said mounting means, said support means being capable of rotatably supporting said fan means in operative relation to said motor means.
7. An apparatus as claimed in claim 6, wherein said support means comprises a support bracket substantially fixedly attached to said mounting means, portions of said support bracket extending around said motor means and said fan means.
8. An apparatus as claimed in claim 6, wherein said support means comprises a hollow cylindrical portion of said mounting means, said hollow cylindrical portion extending through and operatively supporting said stator means and said fan means.
9. An apparatus as claimed in claim 1, 2, 3 or 4, wherein said mounting means comprises a base plate capable of being mounted on a face flange of said electric motor, said face flange conforming to standard dimensions.
10. An electric motor having an independently driven cooling system, said cooling system comprising:
mounting means capable operatively securing said system to an end of said electric motor;
motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means; and fan means drivably coupled to said motor means.
mounting means capable operatively securing said system to an end of said electric motor;
motor means having an annular configuration such that an end of the shaft of said motor can operatively protrude into the interior of said motor means; and fan means drivably coupled to said motor means.
11. An electric motor as claimed in claim 10, wherein said motor means comprises:
stator means substantially fixedly mounted on said mounting means, said stator means having an annular configuration such that an end of the shaft of said electric motor can operatively protrude into the interior of said stator means; and annular rotor means operatively disposed about said stator means, said rotor means being drivably coupled to said fan means.
stator means substantially fixedly mounted on said mounting means, said stator means having an annular configuration such that an end of the shaft of said electric motor can operatively protrude into the interior of said stator means; and annular rotor means operatively disposed about said stator means, said rotor means being drivably coupled to said fan means.
12. An electric motor as claimed in claim 10, wherein said fan means includes a fan disc rotatably supported in spaced relation to said motor means, a peripheral edge of said fan disc being substantially fixedly attached to said rotor means.
13. An electric motor as claimed in claim 11, wherein said rotor means is operatively supported about said stator means by said fan disc.
14. An electric motor as claimed in claim 12 or 13, wherein said fan disc has an annular configuration.
15. An electric motor as claimed in claim 10, 11, 12 or 13, further comprising support means depending from said mounting means, said support means rotatably supporting said fan means in operative relation to said motor means.
16. An electric motor as claimed in claim 15, wherein said support means comprises a support bracket substantially fixedly attached to said mounting means, portions of aid support bracket extending around said motor means and said fan means.
17. An electric motor as claimed in claim 15, wherein said support means comprises a hollow cylindrical portion of said mounting means, said hollow cylindrical portion extending through and operatively supporting said stator means and said fan means.
18. An electric motor a claimed in claim 10, 11, 12 or 13, wherein said mounting means comprises a base plate capable of being mounted on a face flange of said electric motor, said face flange conforming to standard dimensions.
19. An electric motor as claimed in claim 10, 11, 12 or 13, wherein said cooling system is mounted on the non-drive end of said electric motor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002106052A CA2106052C (en) | 1993-09-13 | 1993-09-13 | Cooling system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002106052A CA2106052C (en) | 1993-09-13 | 1993-09-13 | Cooling system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2106052A1 CA2106052A1 (en) | 1995-03-14 |
| CA2106052C true CA2106052C (en) | 1997-08-19 |
Family
ID=4152306
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002106052A Expired - Lifetime CA2106052C (en) | 1993-09-13 | 1993-09-13 | Cooling system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2106052C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102009050693A1 (en) * | 2009-10-26 | 2011-04-28 | Ralph Schelle | Electrical machine e.g. generator, cooling method, for use in small hydro electric power plant, involves regulating and/or controlling rotation of axial blowers depending on detected operating temperature of electrical machine |
-
1993
- 1993-09-13 CA CA002106052A patent/CA2106052C/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102009050693A1 (en) * | 2009-10-26 | 2011-04-28 | Ralph Schelle | Electrical machine e.g. generator, cooling method, for use in small hydro electric power plant, involves regulating and/or controlling rotation of axial blowers depending on detected operating temperature of electrical machine |
Also Published As
| Publication number | Publication date |
|---|---|
| CA2106052A1 (en) | 1995-03-14 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request |