Patent Application
20120080983
The present disclosure relates generally to a cooling system for an electrical motor. More particularly, the disclosure relates to a cooling system for a stator of an electrical motor.
For electric motors or generators, particularly those used in stationary applications, reasonable cooling is accomplished by using air cooling and motor housings that serve as heat sinks. Traction motors are typically forced-air cooled with a blower. Ducting is used to route air into and out of the motor or generator. However, in certain applications, air cooling is not practical on account of the blower and ducting requirements.
Air cooling is often considered inadequate, particularly for electric motors on powerful automobiles or machines that are subject to varied temperature ranges and environments. The air for cooling may be dusty or dirty or the electric motors themselves may become coated with mud and dust, reducing the ability to cool the electric motors with air. In order to maintain cooling uniformity in diverse environments, electric motors using liquid cooling have been developed. In such motors, oil or water systems that already exist on the vehicle may be used to facilitate cooling.
Although liquid cooling enables the use of fluids readily available on the vehicle and is exceedingly effective in cooling electric motors, it is a much more expensive and complex way of cooling. The complexity associated with liquid cooling is generally on account of the routing of the coolant through and over the electric motors or generators to achieve adequate cooling.
U.S. Patent Application Publication No. 2008/0100159 A1 to Dawsey et al. describes a cooling system comprising a coaxial stack of laminates with each identical laminate directly abutting the adjacent laminate. The peripheral edge of each laminate is provided with multiple projecting pins. The projecting pins cooperate with a jacket surrounding the stator to provide a cooling space through which the cooling fluid flows. The pins of adjacent laminates are misaligned to form channels through which the cooling fluid may flow. Though the misaligned pins generate turbulence and may enable the cooling fluid to reach a greater area, they may overly reduce the flow of the cooling fluid over the electric motors or generators, causing inefficiency. Accordingly, there is a requirement for a cooling system for electric devices that is efficient, cost effective and less complex.
A stator of an electric motor is disclosed that includes a plurality of laminates, each laminate in the plurality of laminates including a peripheral edge defining a notch. The plurality of laminates are arranged such that the notches form a substantially helical channel along a periphery of the stator.
A stator of an electric motor is disclosed that includes a plurality of laminates including a plurality of laminate subsets. The laminates in each laminate subset are arranged with the notches aligned to define a passage. The laminate subsets are arranged such that the passages defined by the laminate subsets form a substantially helical channel along the periphery of the stator.
An electric motor is disclosed that includes a rotor having an axis and being rotatable about the axis. A stator is positioned about the rotor and includes a plurality of laminates with each laminate in the plurality of laminates including a peripheral edge defining a notch. The plurality of laminates includes a plurality of laminate subsets, with the laminates in each laminate subset arranged with the notches aligned to define a passage. The laminate subsets are arranged such that the passages defined by the laminate subsets form a substantially helical channel along the periphery of the stator.
The cooling system 14 is configured to circulate a heat-transferring medium (not shown) and keep the electric motor 16 and/or the power source 12 from overheating. The heat-transferring medium may be a low or high pressure fluid. Low-pressure fluids may include, by way of example, water and oils such as engine oil, brake oil, or any other low-pressure fluid known for transferring heat. High-pressure fluids may include by way of example, nitrogen, helium or other high-pressure fluids known for transferring heat. The cooling system 14 may comprise a heat exchanger 18, a fan 28, and a source 30 of the heat transferring medium.
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The shaft 32 of the electric motor 16 may be a cylindrical component or may be configured to any other shape known in the art. The shaft 32 transmits power into and/or out of electric motor 16 and may be connected to housing 52 by means of one or more bearings 60. The shaft 32 may extend beyond the housing 52 from one or both ends of the housing 52. Alternatively, multiple shafts (not shown) may be incorporated within the electric motor 16.
The shaft 32 is fixed to the rotor 34 so that as the shaft 32 rotates, it drives the rotor 34. Rotor 34 may include a stack of laminates (not shown). The stack of laminates may be fastened to shaft 32 by welding, by threaded fastening or by other methods known in the art. The rotor 34 is housed within the stator 36 and is configured to rotate within the stator 36 to create torque. Stator 36 includes a stack of laminates 38, each laminate 38 having a peripheral edge 16. The windings (not shown) formed of conducting material are arranged along the periphery of the stator 36.
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The cooling jacket 62 may be a cylindrical housing for the stator 36 and is deployed to transfer heat to and from the stator 36. The cooling jacket 62 and the periphery of the stator 36 define channels in fluid communication with the cooling system 14. The cooling jacket 62 may comprise an inlet manifold 44 and an outlet manifold 46. The inlet manifold 44 of the cooling jacket 62 is connected to an inlet port 48 of the housing 52 and the outlet manifold 46 of the cooling jacket 62 is connected to an outlet port 50 of the housing 52. The inlet port 48 of the housing 52 is connected to supply conduit 24 of the cooling system 14 and the outlet port 50 of the housing 52 is connected to the return conduit 26 of the cooling system 14.
The notches 66 may be arcuate, rectangular, triangular or other known shapes. The number of notches 66 on the laminate 38 may also be determined by the oil flow rate and the surface area of the stator 36 that is to be cooled.
Each laminate 38 also has a plurality of teeth 70 formed on its inner edge 68 and windings (not shown) may be configured at both edges of the laminates 38. The laminates 38 may be made of steel or any other material suitable for forming stators.
The laminates 38 may be substantially identical such that each has a notch 66 of the same dimensions. Alternatively, some laminates 38 may have notches 66 sized differently from other laminates 38. The laminates 38 with differently sized notches 66 may be used as transition laminates 64 between laminates 38 having similar sized notches 66.
In the embodiment illustrated, each of the laminate subsets 72 is separated from one or two adjacent laminate subsets 72 by a plurality of transition laminates 64 to form the substantially helical channel 74. The notch 66 defined by each of the transition laminates 64 is larger in width than the passages 73 formed by each of the laminate subsets 72. In the embodiment illustrated, the notches 66 of the plurality of transition laminates 64 are aligned.
Various forms of the channel may be formed by different arrangement of the laminates 38. By way of example, in the fourth embodiment described above, each laminate 38 may be separated from a subsequent laminate 38 by a transition laminate 64 having a notch 66 with different dimensions. The laminates 38 may be arranged such that the notches 66 form a plurality of substantially helical channels 74 along the periphery of the stator 36. The plurality of substantially helical channels 74 may extend in the same direction or may extend in different directions. Similarly, the plurality of substantially helical channels 74 formed on the periphery of the stator 36 may have the same angle or may have different angles. The laminates 38 may also be arranged such that the plurality of channels may or may not be in fluid communication with each other.
The substantially helical channel 74 formed on the periphery of the stator 36 and surrounded by the cooling jacket 62 provides a path for the flow of the heat transferring medium. The heat transferring medium enters the stator 36 from the inlet manifold 44 via inlet port 48, and leaves the stator 36 through the outlet manifold 46 via outlet port 50. The heat transferring medium is returned to the heat exchanger 18 which removes the heat from the heat transferring medium. The supply conduit 24 of the heat exchanger 18 returns the heat transferring medium to the inlet manifold 44 of the stator 36 of the electric motor 16 to provide continuous and circulated cooling.
Alternatively, the laminates 38 may be arranged such that some of the heat transferring medium is directed back along the substantially helical channels 74 of the stator 36.
For laminates 38 having a plurality of notches 66 and consequently defining a plurality of substantially helical channels 74 along the periphery of the stator 36, multiple inlet manifolds 44 may be provided, each inlet manifold 44 in fluid communication with the inlet port 48. Similarly, multiple outlet manifolds 46 may be provided, each outlet manifold 46 in fluid communication with the outlet port 50. Each inlet manifold 44 will supply the heat transferring medium for flow through its respective channel from the inlet port 48 and each outlet manifold 46 will direct the heat transferring medium to the outlet port 50.
The substantially helical channels 74 generate a swirl of the heat transferring medium around the stator 36, as opposed to travel in straight or wavy paths. Travel of the heat transferring medium in a substantially helical manner around the stator 36 generates turbulence in the heat transferring medium without obstructing the flow of the heat transferring medium. The substantially helical channels 74 of the cooling system 14 also increase the cooling efficiency of the electric motor 16 without increasing its size or weight. Such benefits may transform into higher specific power, and/or lower manufacturing costs for electric machines, as well as other devices using above-described cooling systems 14.
The cooling system 14 as described may be used with any electric motor 16 or generator as well as other electrical devices such as transformers. Such electric devices may also be used in any environment including in particular for cooling electric motors 16 used on mobile vehicles or work machines.
It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system without departing from the scope of the invention. Other embodiments of the stator will be apparent to those skilled in the art from consideration of the specification. It is intended that the specification and examples be considered as exemplary only, with a true scope of the invention being indicated by the following claims and their equivalents.
