WO2002035687A1 - High speed electric machine - Google Patents

Abstract

The invention relates to a high speed electric machine (10) comprising a rotationally mounted rotor (11) which is separated by a gap (14) and concentrically surrounded by a stator (12) with two winding heads, in addition to comprising means (20,..,28) for cooling the rotor (11) and the stator (12), enabling a cooling agent, especially cooling air, to be circulated through the rotor (11) and stator (12), whereby the heat which is received from the cooling agent or cooling air is removed once again in a cooling apparatus (20). The discharge of lost heat is improved by guiding the cooling agent or cooling air in substantially independent, preferably parallel, first and second cooling circuits (27a,b or 26a,b) for the stator (12) and the rotor (11), and by embodying or arranging the first and second cooling circuits (26a,b; 27 a, b) symmetrically with respect to the centre of the machine (43).

Description

 DESCRIPTION

HIGH SPEED ELECTRIC MACHINE

TECHNICAL AREA

The present invention relates to the field of electrical machines. It relates to a high-speed electrical machine according to the preamble of claim 1.

STATE OF THE ART

The cooling of fast-running electrical machines, in particular asynchronous motors, in the power range from 1 to 20 MW places high demands on the selection of a suitable cooling concept and the design of the individual components due to the high peripheral speeds of the rotor. The electrical power loss to be dissipated generally also reaches values in the rotor that require internal cooling. A heat dissipation alone over the The air gap between the rotor and stator and over the end faces of the rotor is often not sufficient to comply with the temperature limit values determined by the respective insulation class. A special position is occupied by machines that can be cooled with a medium under high pressure. Here, for example, motors for driving pipeline compressors are to be mentioned, which are integrated in the natural gas pipeline and through which the pumped medium (methane) flows under a pressure between 40 and 70 bar. In this case, cooling of the rotor interior may not be necessary.

For applications that require a flow through the rotor, two opposite requirements have to be met, which are of crucial importance, in particular with rotor peripheral speeds in the transonic range. On the one hand, reliable heat dissipation must be ensured by the provision of a sufficient coolant mass flow. On the other hand, there is a demand for a limitation of ventilation losses that are proportional to the mass flow and to the second or third power of the circumferential rotor speed and that can significantly impair the overall efficiency of the machine. Furthermore, the coolant can be heated in the flow through the rotor such that the outlet temperature is above the permissible material temperature of the stator. Thus, the established cooling schemes of standard machines operating in the speed range between 3000 and 3600 rpm, which provide a sequential flow through the rotor and stator, cannot be used.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to provide a solution concept for cooling high-speed electrical machines, in particular asynchronous machines, which enables both efficient dissipation of the heat losses and extensive minimization of the ventilation losses. Beyond that This solution concept also gives considerable advantages in terms of the operating costs of the machine.

The object is achieved by the entirety of the features of claim 1. The essence of the invention is to provide separate first and second cooling circuits for cooling the stator and rotor, which are formed or arranged symmetrically to the machine center. In order to circulate the cooling medium or the cooling air, an additional fan that can be regulated independently of the machine is preferably connected upstream or downstream of the cooler.

A preferred embodiment of the invention is characterized in that the cooling medium or the cooling air in the second cooling circuits for cooling the rotor flows in opposite directions from the end faces to the center of the rotor through axial channels accommodated in the rotor, and in order to compensate for the pressure losses occurring in the rotor flow Blading is attached to each end of the rotor.

The axial channels of the second cooling circuits are either offset from one another and extend from the end faces of the rotor essentially through the entire active part of the rotor and end at the end in the air gap. Or they extend from the end faces of the rotor to a radial gap which is arranged in the center of the machine and is connected to the air gap and opens into the radial gap.

Since a further use of the heated cooling medium from the rotor does not make sense, the heated cooling medium (cooling air) which has emerged from the axial channels into the air gap (cooling air) is preferably at the front ends of the air gap via radial channels running through the stator within the second cooling circuits returned to the cooler. The cooling is further simplified if the cooling medium or the cooling air in the second cooling circuits is passed through the winding overhangs before entering the rotor.

A further preferred embodiment of the invention is characterized in that the machine has a machine housing which exits the cooling medium or the cooling air in the first and second cooling circuits from the cooler into the interior of the machine housing, and in that the air gap on the end faces through seals is sealed. This considerably simplifies the construction of the cooling system.

Another preferred embodiment of the invention is characterized in that radial cooling slots are provided in the stator for cooling the stator, which are divided into slot segments by a tangential segmentation, that each in the first cooling circuits by means of a collecting and distributing device arranged on the back of the stator Slot segment cold cooling medium or cold cooling air is fed from the cooler and heated cooling medium or heated cooling air is led away from the slot segment and back to the cooler, and that the cooling medium or the cooling air flows inside the slot segments in a segment half from the outside to the inside, below which Conductor rods of the stator is deflected and flows out of the slot segment again in a second segment half.

Further embodiments result from the dependent claims.

BRIEF EXPLANATION OF THE FIGURES

The invention will be explained in more detail below on the basis of exemplary embodiments in connection with the drawing. Show it Fig. 1 shows a first preferred in a schematic longitudinal section

Embodiment of an electrical machine according to the invention;

2 shows, in a representation comparable to FIG. 1, a second preferred exemplary embodiment of an electrical machine according to the invention; and

Fig. 3 in cross section an exemplary segmented stator cooling

1 or 2.

WAYS OF CARRYING OUT THE INVENTION

In Fig. 1, a first preferred embodiment of a high-speed electrical machine according to the invention is shown in a schematic longitudinal section. The electrical machine 10 comprises a rotor 11, which is rotatably mounted in two bearings 15 and 16 with a rotor shaft 13 about an axis of rotation 17. The rotor 11 is coaxially surrounded by a stator 12 provided on the end faces with winding heads 18 and 19, of which only the upper half is shown in FIG. 1 for the sake of simplicity. Rotor 11 and stator 12 are separated from one another by an air gap 14. A cooler 20, through which a cooling medium, preferably air, flows, is arranged in the upper area of the machine 10 within a machine housing 33. The flow of the cooling air through the cooler 20 is brought about by an additional fan 21, which in the example shown is placed behind the cooler 20 in the flow direction, but can also be arranged in front of the cooler 20.

An essential feature of the cooling concept shown in FIG. 1 is the use of largely independent first and second cooling circuits 26a, b and 27a, b for the rotor 11 and the stator 12. The first two cooling circuits 26a and 26b as well as the two second cooling circuits 27a and 27b are constructed or arranged symmetrically to the machine center 43. In this way, each of the two components 11, 12 is supplied directly and optimally with cold air. The additional fan (external fan) 21, which is connected downstream of the cooler 20, blows the cold air freely into the interior of the machine housing 33. The inflow into the stator 12 takes place via the back of the stator, on which a corresponding collecting and distributing device 28 is provided. The rotor 11 is supplied with cooling air by means of blading 29 or 30 attached to the end of the rotor shaft 13. The air streams sucked in by the rotor 11 are previously passed over the winding overhangs 18, 19 in order to ensure reliable dissipation of the electrical power loss here as well.

The entry of the cooling medium into the rotor 11 is always a critical component in machines with high peripheral speeds. High differential speeds between the fluid and the rotating walls can cause severe flow separation and thus high pressure losses. These may exceed the pressure build-up of the commonly used external fans many times over, so that the mass flow required for cooling can ultimately not be fed into the rotor 11. In order on the one hand to keep the entry losses as low as possible and on the other hand to generate a pressure build-up that compensates for the friction losses in the rotor 11, a radial or diagonal blading 29 or 30 attached to the rotor shaft 13 is attached to the end faces of the active rotor part. The flow through and cooling of the rotor 11 takes place by means of axial channels 36, 37. The cooling channels 36 and 37 emanating from the left and right side of the machine are offset from one another in the exemplary embodiment in FIG. 1, so that both partial flows of the first cooling circuits 26a, b are almost Flow through the entire active part and exit radially into the air gap 14 at the opposite machine end (see the corresponding flow arrows in the rotor 11 of FIG. 1). This arrangement is particularly suitable for laminated rotors or rotors 11 consisting of disks and leads to a very homogeneous temperature distribution in the axial direction. Another variant for the arrangement of the cooling channels in the rotor 11 is shown in the exemplary embodiment in FIG. 2. Here, the left and right axial channels 36 'and 37' need not be offset from one another. The axial channels 36 ′, 37 ′ end in the machine center 43 and open into a radial gap 38, so that the rotor cooling air exits in the middle of the air gap 14.

Since the temperature of the rotor cooling air can be in the range of the permissible material temperatures of the stator 12, further use of the rotor cooling air for component cooling is not expedient. For this reason, the warm air is discharged through radial channels 34, 35 in the area of the press plates of the stator 12. The effective cross-sectional area of these radial channels 34, 35 is to be dimensioned as large as possible in order to increase the pressure losses and also the heat exchange with the stator material minimize.

At the exit of the radial channels 34, 35 in the stator 12, the cooling medium flows into ring collectors 22 and 23, respectively. The ring collectors 22, 23 are in turn connected to the cooler 20 and the external fan 21 via pipes 24, 25.

High air friction losses occur in the air gap of high-speed electrical machines, which, like the electrical losses, must be dissipated. In the exemplary embodiment shown in FIG. 2, the frictional power is dissipated via the rotor cooling air emerging in the center of the machine 43. In contrast, in the concept shown in FIG. 1, it must be avoided that the air in the air gap 14 heats up in an uncontrolled manner. For this reason, there is an additional injection of cold air in the machine center 43, which mixes with the hot rotor air flow at the ends of the air gap.

Since the pressure level in the air gap 14 is lower than outside in the machine housing 33, a seal 31, 32 is required at both ends of the air gap 14. This is to prevent cold air from getting directly into the warm air collector (ring collector 22, 23). The seals 31, 32 can be designed, for example, as labyrinth seals. Various concepts can be used for cooling the stator 12, which, however, should have a seal to the air gap 14 as a "common denominator", so that the separation of the rotor and stator coolant flows is ensured. The principle is shown here using the example of a tangential segmentation of the radial cooling slots of the stator. However, axial chambering is also possible, as is usual in turbogenerator construction.

The cooling air is supplied to the stator radially into the interior of the stator in the case of the “tangential cooling” shown in FIG. 3 from the machine housing 33. The cold air 41 flows in individual slot segments 40 past the conductor bars 39 to an inner boundary surface which seals the slot segments 40 with respect to the air gap 14. This inner boundary can be created, for example, by a cylindrical insert ("air gap cylinder"). Below the conductor bars 39, the flow is deflected by 180 °. The hot air 42 flows out of the stator 12 in a manner similar to the inflow. The outflowing cooling medium is finally brought together in the collecting channels 28 of the collecting and distributing device 28 distributed over the circumference and introduced from there into the ring collectors 22, 23 which are arranged in the region of the press plates (cf. FIGS. 1 and 2).

Overall, the invention results in a high-speed electrical machine which is characterized by efficient dissipation of heat losses and extensive minimization of ventilation losses and which has considerable advantages in terms of operating costs.

LIST OF REFERENCE NUMBERS

10 electric machine (high-speed)

11 rotor

12 stator

13 rotor shaft Air gap, 16 bearings (rotor)

Rotation axis, 19 winding head

cooler

Additional fan, 23 ring collectors (hot air), 25 piping (hot air) a, b cooling circuit (rotor) a, b cooling circuit (stator)

Collection and distribution device, 30 blading (rotor), 32 seal

Housing, 35 radial channel, 37 axial channel \ 37 'axial channel radial gap

Head of staff

slot segment

cold air

hot air

machine center

Claims

1. High-speed electrical machine (10), comprising a rotatably mounted rotor (11), which rotor (11) is concentrically surrounded by an air gap (14) separated from a stator (12) with two winding heads (18, 19), and means (20, .., 28) for cooling the rotor (11) and stator (12), by means of which a cooling medium, in particular cooling air, is sent into a circuit through the rotor (11) and the stator (12) and thereby by the Cooling medium or the heat taken up in the cooling air is withdrawn again in a cooler (20), characterized in that the cooling medium or the cooling air in largely independent, preferably parallel, first and second cooling circuits (27a, b and 26a, b) for the stator (12) and the rotor (11) is guided, and that the first and second cooling circuits (26a, b; 27a, b) are designed or arranged symmetrically to the machine center (43). 2. Machine according to claim 1, characterized in that an additional fan (21) which can be regulated independently of the machine (10) is connected upstream or downstream of the cooler (20) for the circulation of the cooling medium or the cooling air. 3. Machine according to one of claims 1 and 2, characterized in that the cooling medium or the cooling air in the second cooling circuits (26a, b) for cooling the rotor (11) through axial channels (36, 37) accommodated in the rotor (11) or 36 ', 37') flows in opposite directions from the end faces to the center of the rotor (11), and that in order to compensate for the pressure losses occurring during the flow through the rotor, blading (29, 30) is attached to the end faces of the rotor (11). 4. Machine according to claim 3, characterized in that the axial channels (36, 37) of the second cooling circuits (26a, b) are arranged offset from one another and from the end faces of the rotor (11) essentially through the extend the entire active part of the rotor (11) and end at the end in the air gap (14). 5. Machine according to claim 3, characterized in that the axial channels (36 ', 37') of the second cooling circuits (26a, b) from the end faces of the rotor (11) to one in the machine center (43) arranged with the radial gap (38) connected to the air gap (14) and open into the radial gap (38). 6. Machine according to one of claims 4 and 5, characterized in that within the second cooling circuits (26a, b) that (s) from the axial channels (36, 37; 36 ', 37') emerged into the air gap (14) heated cooling medium (cooling air) is returned to the cooler (20) at the front ends of the air gap (14) via radial channels (34, 35) running through the stator (12). 7. Machine according to one of claims 3 to 6, characterized in that the cooling medium or the cooling air in the second cooling circuits (26a, b) before each entry into the rotor (11) via the winding heads (18, 19) , 8. Machine according to one of claims 1 to 7, characterized in that the machine (10) has a machine housing (33) that the cooling medium or the cooling air in the first and second cooling circuits (26a, b; 27a, b) the cooler (20) exits into the interior of the machine housing (33), and that the air gap (14) is sealed at the end faces by seals (31, 32). is. 9. Machine according to one of claims 1 to 8, characterized in that for cooling the stator (12) in the stator (12) radial cooling slots are provided, which are divided by a tangential segmentation into slot segments (40) that by means of a Back of the stator (12) arranged collecting and distributing device (28) in the first cooling circuits (27a, b) each slot segment (40) cold cooling medium or cold cooling air from the cooler (20) and heated cooling medium or heated cooling air from the slot segment (40) away and returned to the cooler (20), and that the cooling medium or the cooling air within the slot segments (40) flows in a segment half from the outside inwards, is deflected below the conductor bars (39) of the stator (12) and flows out of the slot segment (40) in a second segment half. 10. Machine according to claim 9, characterized in that the cooling slots of the stator (12) are sealed off from the air gap (14).