Patent Application
20130241326
The present invention is related to dynamoelectric machines and, in particular, to cooling of dynamoelectric machines.
A dynamoelectric machine is any type of machine that can generate motion from electricity or vice-versa and includes, for example, motors and generators. As such, the term “machine” as used herein shall refer to both motors and generators unless specifically limited to the contrary. These machines include both a rotor and a stator separated by a rotor-stator gap. The machine can be cooled by the flow of a liquid coolant flow through the rotor-stator gap. Such a machine is referred to as a liquid cooled machine.
According to one embodiment, an electric motor that includes an outer housing, a stator disposed within the outer housing and a rotor disposed within the stator that, in combination with the stator, defines a rotor-stator gap between them, is disclosed. The rotor of this embodiment includes a main rotor body and a rotor body extension extending axially from an end of the main rotor body. In this embodiment, the main rotor body includes an axial hole formed at least partially along a length thereof.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
a-4c show a process by which a stator channel may be formed in the rotor shown in
One environment where liquid cooled machines are utilized is on aircrafts. It has been discovered, however, that in such situations the liquid coolant flow the rotor-stator can result in windage losses. The windage losses results from the friction between the rotor and the coolant. In some cases, the losses can equal up to 70-80% of the machine's electromagnetic heat loss. As a result, and in the event that the machine is a motor, more motor input power is required from the aircraft electrical power system. In addition, increased windage loss results in lower motor efficiency such that motor efficiency is in the 83-85% range. Embodiments of the present invention are directed to liquid cooled machines having reduced windage losses. This can be accomplished, for example, by flowing the liquid coolant through one or more of: an internal portion of the rotor and an external portion of the stator. In one embodiment, no cooling liquid is allowed to pass into the rotor-stator gap. In one embodiment, fluid is only passed through the rotor and the stator is cooled by providing a high conductivity thermal gap pad between an end turn of the stator and the outer housing of the machine.
To provide context, a cross-section of a prior art permanent magnet motor 100 is illustrated in
The cooling fluid is initially drawn into an inlet plenum 108 (not shown) formed in the pump component 102. The fluid is then drawn into a volute 111 formed between the pump component 102 and the motor 100 by the rotation of an impeller 106 and then expelled out of the pump 104 at an outlet (not shown) of the volute 111. However, not all of the fluid is expelled out of the volute 111. In particular, some of the fluid travels into and through the motor 100 and serves to cool it. The path of the fluid is shown by arrows A.
As illustrated, the impeller 106 is directly coupled to the rotor 114 of the motor 100. A thrust bearing 150 is disposed between the impeller 106 and the inlet plenum 108. Fluid that is not expelled from the volute 111 can enter the motor 100 by passing through journal bearing 152 as shown by arrow A′. Thereafter, the fluid enters the interior 109 of the motor 100 and then travels through the rotor-stator gap 110, as described above. The fluid then passes through one or more bearings such as journal bearing 160 and bumper bearing 162 and is drawn back towards the volute 111 through an inner channel 112 of the rotor 114 and provided back into the pump component 102. As described above, having the fluid pass through the rotor-stator gap 110 can result in windage losses.
The following description will assume that the motors disclosed hereafter include are disposed such that a cooling fluid can be provided to them. For instance, the motors could be coupled to a pump portion to form a volute in which an impeller is disposed. The motor turns the impeller to expel a fluid and some of the fluid is drawn into the motor and used to cool the motor.
The rotor 201 includes one or more permanent magnets 204 disposed about a rotor body 206. The permanent magnets 204 are disposed in a rotor sleeve that includes end plates 208. In the illustrated embodiment, the rotor body 206 includes a rotor body extension 207 that has smaller outer diameter than other portions of the rotor body 206.
Referring now to
Arranged about the rotor body 206 are the permanent magnets 204 described above. The permanent magnets 204 are surrounded by a rotor sleeve 304. In one embodiment, the magnets are arranged such that a channel 308 is created between adjacent magnets 204 and the rotor sleeve 304.
As illustrated, the rotor 201 further includes a plurality of axial holes 340 formed in the rotor body 206. These axial holes 340 extend axially along a portion of the rotor 201. In an alternative embodiment, and as disclosed further below, the axial holes 340 could extend along the entire length of the rotor 206. Referring now to both
In
In
Regardless of the orientation of the rotor holes 340 and the channels 308, the rotor holes 340 form part of a rotor channel (
a-4c show how the rotor channels 350 can be formed in the rotor 201. In particular, one or more axial holes 340 are axially formed (e.g., drilled) though the rotor body extension 207 and into another portion of the rotor body 206 that shall be referred to herein as the main rotor body 209 (
Radial orifices 344 are formed in both the main rotor body 209 and the rotor body extension 207 such they contact the axial holes 340 (
An end portion of the axial holes 340 is then filled with a plug 346 such that a rotor channel 350 is formed whereby fluid flows into the radial orifice 344 on the rotor body extension 307 through a portion of the main rotor body 209 and exits the main rotor body 209 at an outer diameter thereof. Of course, fluid could also flow in the opposite direction.
Referring again to
The motor 400 further includes an outer housing 420 that surrounds the stator 430. In this embodiment, a housing channel 422 or a plurality of axially or circumferentially disposed channels are provided within the outer housing 420 through which cooling fluid may flow. The cooling fluid enters the housing channel 422 through an opening 421 in the outer housing 420.
The stator 430 can include end turns 432. In one embodiment, a highly conductive thermal gap pad 434 is disposed between the end turns 432 and the outer housing 420 to improve transfer of heat from the end turns 432 to the outer housing 420. The heat is then carried at least partially away by the fluid traveling through the housing channels. 422.
As illustrated, the fluid leaves the housing channel 422 and passes through at least journal bearing 460. Seals 462 are provided around the rotor 402 to keep the fluid from entering the rotor-stator gap 450. The fluid is then forced to travel through rotor channels 470 formed in the rotor 401. As can best be seen in
Referring again to
In summary, in this embodiment, liquid from pump outlet enters the motor housing channels 422 and then flows axially through these channels to the distal end of the motor 400. After passing through the journal bearing 460 at the distal end of the motor 400, the fluid is denied entry into the rotor-stator gap 450 by seals 462 and, as such, passes through rotor channels 470 and then, ultimately, back to the pump outlet. In this manner, heat from or both of stator and rotor can be carried away by the liquid.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
