CN1302470A - Electric machine - Google Patents

Abstract

In an electrical machine such as electric motor or generator comprising a casing which contains rotatable components air direction means is provided and constructed and arranged to direct an air current over the exterior of the machine. The air direction means may be in form of a cowl which may be an extension of or secured to a fan housing.

Description

motor

The invention relates to a motor, in particular to an AC motor.

It is known that electrical machines generate undesirable heat during operation, eg due to winding resistance and friction in bearings. It is also known to provide cooling means and fans to blow air through the cooling ducts. For example GB-2115987B discloses an AC motor with cooling ducts, some passing through the stator and some passing through the rotor.

It is an object of the present invention to provide another cooling device or alternatives.

In accordance with the present invention, an electric machine includes air guiding means configured and dimensioned to direct air flow through the exterior of the machine.

The air guiding means may enclose at least part of the exterior of the machine and comprise a shroud which is either an extension of the fan housing or is fixed to the fan housing. The shroud may extend from the fan housing at one end of the machine and cover at least part of the exterior of the machine without air gaps, such as air guide slots, between the shroud and the exterior.

The shroud may be fixed to any suitable machine part. For example, if the machine includes an AC motor having a stator and a rotor each comprising laminations, the guide shroud may be secured to the stator laminations at one end of the motor, a pressure plate holding the stator laminations together, or a stand.

The air guiding means may comprise an air deflector in the fan housing, of frusto-conical or cylindrical shape. The deflector can be integrally formed in the casing, or fixed on it.

The air guiding device, in particular the shroud or the baffle, can also guide the air through at least one opening, eg in the stator laminations, in the rotor laminations and/or between the stator and the rotor.

The air guiding means may comprise at least one protrusion fixed to or formed on or in close proximity to the outer surface of the machine to allow cooling air to "scrub" the outer surface. The protrusions may define one or more air guide slots through which air passes and may be integrally formed with some or all of the shroud, end brackets, pressure plate or lamination.

Stator winding protection shrouds may be provided to cover the windings eg at each end of the stator. The shroud can be attached to the end frame, the pressure plate or the stator itself.

An end plate may be provided, completely enclosed within one of the two brackets. The end plate may be fixed to a portion of a bearing supported by one of the two brackets in which the shaft supporting the rotor rotates.

Referring now to the drawings, there is illustrated by way of example only an embodiment of the invention, namely an AC induction motor, in which:

Fig. 1 represents the longitudinal sectional view through motor, in this example, this motor is the AC induction motor of the present invention;

Fig. 2 shows a cross-sectional view through the stator core stack along the line II-II in Fig. 1;

Figure 3 shows a perspective view of the stator lamination stack;

Figure 4 shows a perspective view of the pressure plate;

Fig. 5 shows a perspective view of a modified structure of the fan and shroud.

In the accompanying drawings, the AC induction motor shown in particular in FIG. 1 comprises a rotor 10 mounted on a shaft 11 which can be arranged around an axis 0 of bearings 12, 13 arranged in each of end frames 14, 15. -0 rotation, a stack of stators 16 is sandwiched between two pressure plates 17,18, each supporting one of the end frames 14,15.

The rotor 10 comprises a number of circular or pole laminations punched from electrical steel sheet which are held between end rings 19,20. Slots (not shown) are provided in the laminations and extend radially inwardly from the laminations. In these slots bus bars 21 are formed, and the end rings 19, 20 and bus bars 21 are die-cast from an aluminum alloy, forming a well-known squirrel-cage structure. The rotor laminations are likewise provided with a number of circumferentially spaced cooling grooves 22, one of which is shown in FIG. Both the laminated rotor 10 and the rotor end rings 19, 20 are fixed to the shaft 11 for rotation therewith.

The stator 16 has no enclosing casing and consists of laminations punched from electrical steel sheet, having the shape specifically shown in FIG. 2 . Each stator lamination is roughly square, but four corners are removed, so that the overall shape is octagonal, four of which are larger than the remaining four. These iron chips are provided with eight cooling grooves, and the section of each groove is roughly triangular. The cooling trenches are arranged in pairs, one pair adjacent to each short side. These laminations are sandwiched between pressure plates 17, 18 and the assembly is held firmly together by rods 25 which pass through cooling channels 24 in the stator laminations and through corresponding channels 29 in the pressure plates. The ends of these rods are threaded and provided with nuts 28 for tensioning the pressure plates 17, 18, although one end of the rods could be headed and the other end provided with tensioning nuts. Alternatively, the stator laminations may be firmly held between the pressure plates by wedges or welding. These pressure plates are also each provided with cooling grooves 29 which are substantially the same size and shape as the cooling grooves 24 in the stator laminations and which are aligned with each other.

It can be seen from FIG. 2 that the stator core sheet includes a central circular hole 33 and several slots 34 radiating from the circular hole, and the rotor rotates in the circular hole. These slots are filled with stator windings, as shown in Figure 1.

The end frames 14 and 15 are fixed on respective pressure plates, which have substantially the same square shape and size as the pressure plates 17 and 18 in the stator 10 . Each end frame 14 , 15 has an end 30 , 31 extending perpendicularly to the shaft 11 . Each end 30, 31 contains and supports a bearing 12, 13 for rotatably supporting the shaft. The end 30 on the end frame 14 has an end plate within the cavity formed by the end frame 14, which end plate has terminals mounted on an adapter plate which also serves as an end support for the bearing 12. Connecting wires (not shown) run from the stator windings 35 directly to the end plate through holes 37 in the ventilation shield 38 in the end frame and are also connected to the pressure plate 17 . The shaft passes through a central hole 39 in the protective guide. Electrical wires (not shown) from an external power source to the end plates pass through glands (not shown) in appropriate locations in the end plates 14,15. Providing the end plate within the end frame cavity eliminates the need for a normally externally configured end frame and avoids problems associated with the end frame being in a realistically proper position (right or left top).

The other end 31 on the other end frame 15 is provided with openings 40 through which cooling air can be supplied from a fan 41 located outside the end frame 15 . The fan 41 is electrically driven, separate from the AC motor, or can be mounted on the side.

The fan 41 is arranged so as to rotate about the same axis 0-0 as the shaft 11, within a housing 69 made of molded plastic or fabricated material. The housing 69 has a grid 42 in an end wall 43 perpendicular to the axis 0-0, through which air is sucked and forced to flow over the exterior of the motor in a generally axial direction and flow through the respective cooling groove. The cross-sectional shape of the housing is close to that of the end frame 15, but has a horizontal top side 44, two vertical sides 45, 46 and four oblique short sides 47, 48, 49, 50, which are larger than the end frame. The frame 15, the pressure plates 17, 18 and the respective sides of the stator 16 can be seen from FIG. 2 . The top horizontal side 44, the two vertical sides 45, 46 and the upper two short sides 47 and 48, as shown in FIG. The guide cover 60 on both sides. A gap is formed between the inner surface of the guide shield and the adjacent side of the bracket, but not at the lower horizontal side 51 where the housing edge 52 slightly covers the bottom of the end frame 15 . It is also possible to form a small gap at the lower horizontal side 51 , the edge 52 not covering the bottom of the end frame 15 . A short cylindrical baffle 54 is integrally molded or attached to the inner surface of the end wall 43 of the fan housing, which baffle surrounds the fan blades. The radially inner surface 55 of the deflector is frusto-conical and helps direct the air towards the motor.

The two end frames 14,15 of the pressure plates 17,18 and the side surfaces of the laminated stator 16 are all provided with two protrusions 53,56. These projections are aligned parallel to the motor axis 0-0 and serve as guides for air blown by the fan flowing axially along the outer surface of the motor, especially the stator 16, through the gap between the shroud 60 and the end frame 15. Thus, air-guiding grooves are formed between adjacent protrusions.

The protrusion 56 at the bottom provides an elongated stand for the motor to rest on a horizontal support surface, since there is no guide shroud at the bottom, where the air is directed from the fan, except at the edge 52 of the lower side 51 There is a small gap.

In use, the fan 41 sucks air through the grid 42 in the housing 69, and through the groove between the protrusion 53 (and 56 if there is a small gap at the edge of the lower side 51), and through the groove in the end frame. The holes 40 and thereafter force air to flow axially across the motor surfaces through channels in the rotor, through the gap between the stator and rotor, or through the pressure plates and channels 29, 24 in the stator. Allows air to flow in reverse.

A winding protection shroud, similar to shroud 38 covering the left winding as shown in FIG. 1 , may be provided to cover the right stator winding.

In a modification, the protrusions 53 on the top and side surfaces of the right end frame are omitted. Instead, corresponding protrusions 70 are molded together with the inner surface of the guide shield, or fixed to each other, as shown in FIG. 5 .

The invention is applicable to all other types of AC and DC motors having a laminated stator frame construction. This includes stators/rotors with cylindrical, squirrel-cage and non-squirrel-cage poles and varying numbers of poles and phase windings.

Claims (14)

1. An electric machine includes an air guide constructed and arranged to direct air flow over an exterior surface of the machine. 2. 2. An electric machine as claimed in claim 1, characterized in that the air guiding means covers at least a part of the outer surface of the machine. 3. 2. The motor of claim 2, wherein the air guiding means comprises a shroud which is either an extension of the fan housing or is fixed to the fan housing. 4. An electric machine as claimed in claim 3, characterized in that the shroud extends from the fan housing at one end of the machine and covers at least a portion of the outer surface of the machine, a gap being provided between the shroud and the outer surface . 5. The motor according to claim 3 or 4, characterized in that the motor comprises an AC motor with a certain rotor and a rotor, the stator and the rotor are each composed of iron laminations, and the guide cover is fixed on the stator iron laminations and a pressure plate or on the A bracket at one end of the motor, the pressure plate holds the stator laminations together. 6. The motor according to any one of claims 3 to 5, characterized in that the air guiding means comprises an air deflector in the fan housing, the deflector is truncated conical or cylindrical. 7. The motor according to claim 6, characterized in that the deflector is integrally formed in said housing, or connected thereto. 8. An electric machine as claimed in any preceding claim, wherein the air guiding means also guides air through at least one hole in the machine. 9. An electric machine as claimed in any one of the preceding claims, characterized in that the air guiding means comprises at least one protrusion which is fixed to or formed on the outer surface of the machine or is arranged in close proximity thereto. 10. 9. An electric machine as claimed in claim 9, wherein the protrusion defines one or more channels for the passage of air. 11. 4. An electrical machine as claimed in any preceding claim, comprising a stator with windings and a stator winding protective shroud at at least one end thereof. 12. 12. The motor of claim 11, wherein the guide shield is connected to an end frame, a pressure plate or the stator itself. 13. 3. An electric machine as claimed in any preceding claim, comprising two brackets and an end plate completely enclosed within one of the two brackets. 14. An electric machine substantially as herein described with reference to and as shown in the accompanying drawings.

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