Patent Application
20070075595
The present invention generally relates to heat-generating devices and machines, including rotating machines such as electric induction motors. More particularly, the present invention relates to a technique for embedding a cooling coil or conduit in a device or machine component to promote heat dissipation from the device or machine.
Rotating machines of various types are commonly found in industrial, commercial and consumer settings. For instance, in industry, motors are employed to drive various kinds of machinery, such as pumps, conveyors, compressors, fans and so forth, to mention only a few. Conventional alternating current (ac) electric motors may be constructed for single- or multiple-phase power, and are typically designed to operate at predetermined speeds or revolutions per minute (rpm), such as 3600 rpm, 1800 rpm, 1200 rpm, and so on. Such motors generally include a stator comprising a multiplicity of windings surrounding a rotor, which is supported by bearings for rotation in the motor frame. Typically, the rotor comprises a core formed of a series of magnetically conductive laminations arranged to form a lamination stack capped at each end by electrically conductive end rings. Additionally, typical rotors include a series of conductors that are formed of a nonmagnetic, electrically conductive material and that extend through the rotor core. These conductors are electrically coupled to one another via the end rings, thereby forming one or more closed electrical pathways.
In the case of ac motors, applying ac power to the stator windings induces a current in the rotor, specifically in the conductors. That is, at a given point in time, alternating levels and polarities of current are routed through the various coil windings. This varied routing of current results in a dynamic electromagnetic field that induces rotation of the rotor. The speed of this rotation is typically a function of the frequency of ac input power (i.e., frequency) and of the motor design (i.e., the number of poles defined by the stator windings). A rotor shaft extending through the motor housing takes advantage of this produced rotation and translates the movement of the rotor into a driving force for a given piece of machinery. That is, rotation of the shaft drives the machine to which it is coupled.
As will be appreciated, transmission of electricity through the windings of a motor, or the circuitry of an electronic device, and friction between moving and stationary components within devices generate heat, which may interfere with proper operation of the motor or other device. Further, in the case of a motor, heat may be transmitted to the motor from external devices or components coupled to the motor, such as a mining drill driven by a motor. While some devices may adequately dissipate such heat through passive cooling techniques, other devices create more heat than can be effectively dissipated through such techniques. Particularly, in certain demanding applications for motors, such as high speed operation and mining activities, active cooling techniques are desirable to adequately dissipate heat from the motor and facilitate proper operation of the motor. However, inclusion of active cooling systems increases the time, labor, and expense of producing such motors and other devices.
There exists, therefore, a need for machines and devices having efficient cooling systems and an improved technique for producing such systems efficiently while reducing manufacturing costs of the systems.
In accordance with certain embodiments, the present technique provides a device component having a cooling coil embedded in a cast body of the component. The cooling coil includes an internal conduit or passage for transmission of a cooling material through the cooling coil. The cooling coil material has a melting point substantially equal to or less than the melting point of the material of the cast body. Heat is transferred from the device to the cooling material and is thereby removed from the component. The cooling material may be any material with suitable thermal characteristics, including various fluids or gases. By way of example, the device component may be a motor frame having a serpentine or helical cooling coil.
In accordance with another embodiment, the present technique provides a rotating machine having an internal cooling coil embedded within a frame of the machine. The frame material has a melting point generally equal to or greater than the melting point of the cooling coil. A coolant may be routed through the cooling coil to dissipate heat present during operation of the machine. The exemplary apparatus also includes a rotor and stator core disposed within the frame.
Additionally, the present technique provides an exemplary method for manufacturing a device having an embedded cooling coil for dissipating heat in the device. The exemplary method includes the act of disposing a cooling coil in a casting mold for a device component. The method also includes casting the device component in the mold having the cooling coil and circulating a coolant through the cooling coil during at least a portion of the casting step. This results in a device component having the cooling coil embedded within the component, facilitating active cooling of the component during operation.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As discussed in detail below, certain embodiments of the present invention provide components, apparatus, and methods for motors and motor construction. Although the following discussion focuses on induction motors, the present invention also affords benefits to a number of applications, including not only those involving other types of electric motors, such as direct current (dc) motors, or rotating machines, but also those involving heat-generating devices outside the field of motors and rotating machines. Accordingly, the following discussion provides exemplary embodiments of the present invention and, as such, should not be viewed as limiting the appended claims to the embodiments described.
Turning to the drawings,
To induce rotation of the rotor, current is routed through stator windings disposed in the stator, such as those illustrated in
Routing electrical current from the external power source 22 through the stator windings produces a magnetic field that induces rotation of the rotor. A rotor shaft 26 coupled to the rotor rotates in conjunction with the rotor. That is, rotation of the rotor translates into a corresponding rotation of the rotor shaft 26. As appreciated by those of ordinary skill in the art, the rotor shaft 26 may couple to any number of drive machine elements, thereby transmitting torque to the given drive machine element. By way of example, machines such as pumps, compressors, fans, conveyors, and so forth, may harness the rotational motion of the rotor shaft 26 for operation.
Notably, as discussed in greater detail below, frame 12 includes an internal cooling coil for dissipating heat generated by motor 10. Accordingly, frame 12 includes an inlet port 28 for introduction of a cooling material, such as a fluid or a gas, within the cooling coil.
Additional features of exemplary motor frame 12, including certain internal features, are illustrated in
It should be noted that cooling coil 32 may be configured to transmit various coolants. While water is used in one embodiment, utilization of other fluids or gases is also envisaged. When circulated through cooling coil 32, the coolant extracts heat from the system through convection, conduction, or a combination thereof, thereby dissipating heat generated by, or otherwise present in, motor 10. Further, it should also be noted that, while cooling coil 32 is generally serpentine or labyrinthine in shape, other embodiments may include cooling coils of other shapes, such as the helical cooling coil illustrated in
In the exemplary motor 10, a rotor assembly 42 resides within the rotor chamber 38. Similar to the stator core 36, the rotor assembly 42 comprises a plurality of rotor laminations 44 aligned and adjacently placed with respect to one another. Thus, the rotor laminations 44 cooperate to form a contiguous rotor core 46. The exemplary rotor assembly 42 also includes rotor end members 48, disposed on each end of the rotor core 46, that cooperate to secure the rotor laminations 44 with respect to one another. When assembled, the rotor laminations 44 cooperate to form shaft chamber that extends through the center of the rotor core 46 and that is configured to receive the rotor shaft 26 therethrough. The rotor shaft 26 is secured with respect to the rotor core 46 such that the rotor core 46 and the rotor shaft 26 rotate as a single entity, the rotor assembly 42.
The exemplary rotor assembly 42 also includes electrically conductive nonmagnetic members, such as rotor conductor bars 50, disposed in the rotor core 46. Specifically, the conductor bars 50 are disposed in rotor channels 52 that are formed by amalgamating features of each rotor lamination 44. As will be appreciated by one skilled in the art, inducing current in the rotor assembly 42, specifically in the conductor bars 50, causes the rotor assembly 42 to rotate. By harnessing the rotation of the rotor assembly 42 via the rotor shaft 26, a machine coupled to the rotor shaft 26, such as a pump or conveyor, may operate.
To support the rotor assembly 42, the exemplary motor 10 includes front and rear bearing sets 54 and 56, respectively, that are secured to the rotor shaft 26 and that facilitate rotation of the rotor assembly 42 within the stationary stator core 36. During operation of the motor 10, the bearing sets 54 and 56 transfer the radial and thrust loads produced by the rotor assembly 42 to the motor housing. Each bearing set 54 and 56 includes an inner race 58 disposed circumferentially about the rotor shaft 26. The tight fit between the inner race 58 and the rotor shaft 26 causes the inner race 58 to rotate in conjunction with the rotor shaft 26. Each bearing set 54 and 56 also includes an outer race 60 and ball bearings 62, which are disposed between the inner and outer races 58 and 60. The ball bearings 62 facilitate rotation of the inner races 58 while the outer races 60 remain stationary and mounted with respect to the endcaps 14 and 16. Thus, the bearing sets 54 and 56 facilitate rotation of the rotor assembly 42 while supporting the rotor assembly 42 within the motor housing, i.e., the frame 12 and the endcaps 14 and 16. To reduce the coefficient of friction between the races 58 and 60 and the ball bearings 62, the ball bearings 62 are coated with a lubricant.
As discussed above, the exemplary motor 10 produces heat during operation and cooling coil 32 is provided within frame 12 to dissipate such heat. Cooling coil 32 defines a conduit or passageway 64 that enables a coolant to be routed through the cooling coil within frame 12. As noted above, any suitable coolant may be used, such as water, another fluid, or a gas. This coolant absorbs heat from the motor via frame 12 and cooling coil 32. The coolant is then routed from the motor 10, such as through outlet port 30 (
As will be appreciated, other cooling arrangements may be employed in accordance with the present techniques. For instance, an alternative motor frame 72 is illustrated in
An exemplary method 82 for manufacturing an apparatus, such as a motor, having an embedded cooling coil is provided in
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
