Construction of dynamoelectric machines

Sept. 16, 1952 f. j. Johns etal 2,610,992

CONSTRUCTION OF DYNAMOELECTRIC MACHINES

Filed May 16, 1950 2 SHEETS—SHEET 1

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WITNESSES:

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INVENTORS Francis J. Johns &amp; Henry J. Owens. ^BY 7 fATTORNEY

Sept. 16, 1952

F. J. JOHNS ETAL

2,610,992

Filed May 16, 1950

CONSTRUCTION OF DYNAMOELECTRIC MACHINES

SHEETS—SHEET 2

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WITNESSES:

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INVENTORS Francis J. Johns a Henry J. Owens. ^BY 7· 0ATTO

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Patented Sept. 16, 1952

2,610,992

UNITED STATES PATENT OFFICE

2,610,992

CONSTRUCTION OF DYNAMOELECTRIC MACHINES

Francis J. Johns and Henry J. Owens, Buffalo, N. Y., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania

Application May 16, 1950, Serial No. 162,368

Claims. (Cl. 171—123)

The present invention relates to the construction and ventilation of dynamoelectric machines, and more particularly to a construction for a motor-generator set which is. capable of being used as either a water-cooled machine or an aircooled machine, and which is readily adaptable for either type of operation by means of the addition, or omission of a relatively few parts.

The construction of the present invention is especially suitable for motor-generator sets consisting of an electric motor driving a highfrequency alternator, usually of the inductor type,, for supplying high-frequency alternating current. Such sets are frequently used for supplying induction heating equipment, or other equipment where high-frequency current is required. Both water-cooled and air-cooled motor-generator sets of this type have been built, and both types are extensively used. As designed and built heretofore, however, these two types of machines have been of entirely different construction, and have had practically no parts in common. This has meant that water-cooled and air-cooled high-frequency motor-generator sets have had to be designed and built as different, and more or less unrelated, types of machines, and the manufacturers of these machines have had to maintain separate stocks of different parts for the two different types, of motor-generator sets, with corresponding high cost.

The principal object of the present invention is to provide a construction for motor-generator sets which is suitable for operation with either water-cooling or air-cooling, and which can readily be adapted for either type of cooling by the addition or omission of a relatively few parts in the Anal assembly of the machine. This construction materially simplifies the design and manufacture of these machines, and greatly reduces the number of different parts which must be manufactured and stocked, thus reducing the cost of the machine.

Another object of the invention is to provide a motor-generator set having a motor and a generator mounted in a common frame structure, with means for circulating ventilating air in separate paths through the generator and motor within the frame structure, the frame structure being adaptable for operation as either a watercooled or an air-cooled machine by adding or omitting a relatively few parts in. the final assembly of the machine.

A further object of the invention is to provide an air-cooled motor-generator set in which air is admitted at opposite ends of a common frame structure, flows in separate paths through the motor and generator, and is discharged through openings near the center of the frame.

Still another object of the invention is to 5 provide a water-cooled motor-generator set in which air is circulated in separate paths within the frame through the motor and generator and over cooling coils located in housings attached to the opposite ends Of the frame.

Other objects and advantages of the invention will be apparent from the following detailed description, taken in connection with the accompanying drawings, in which

Figure 1 is a view, partly in elevation and 15 partly in longitudinal section, showing a watercooled motor-generator set embodying the invention;

Fig. 2 is a view, partly in elevation and partly in longitudinal section, showing a motor-gen20 erator set of the same construction adapted for air-cooled operation;

Fig. 3 is a transverse sectional view through the generator end of the machine, approximately on the line III—III of Fig. 1, and

Fig. 4 is a transverse sectional view through the motor end of the machine, approximately on the line IV—IV of Fig. 1.

The invention is shown in. the drawing embodied in a motor-generator set consisting of a 30 generator i and a motor 2 supported in a common frame structure 3. As indicated above, the construction of this motor-generator set is such that it can readily be adapted for operation with either water-cooling or air-cooling, the frame 35 structure, and the motor and generator themselves, being the same for either type of operation. The common frame structure 3 is generally cylindrical and is closed at the ends by suitable end members 4. The end member 4 at 40 the left-hand, or generator, end of the machine has two sets of circumferentially disposed, radially spaced openings 5 and 6 formed therein for the passage of ventilating air, and the end member 4 at the right-hand, or motor, end of the machine 45 has two similar sets of radially spaced openings Ί and 8. Larger openings 9 for the passage of ventilating air are disposed circumferentially of the frame structure 3 near the center. A common shaft 10 for both the motor and gen50 erator extends through the frame, structure 3 and is supported in bearings ί ί, of any suitable type, mounted in the end members 4.

The generator I is shown as being an inductor, type high-frequency generator, and has a stator core member 12 mounted in the frame structure

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3. As shown in Fig. 3, the generator stator core ί 2 is generally square in outside configuration, with rounded corners, and is pressed or otherwise secured in a frame ring 13, which in turn is mounted directly in the frame structure 3, by pressing or otherwise. The generally square configuration of the stator core i2 forms large axial air ducts (4 extending between the frame 3 and the sides of the core 12, between the corners of the core. If desired, the straight sides of the core 12 may be provided with grooves 15 to increase the surface area exposed to the ventilating air flowing through the ducts 14, although these grooves may not always be necessary and may be omitted if not needed. The generator stator core has a plurality of slots 16 in its inner periphery, in which the stator winding (7 is disposed, and a directcurrent exciting winding 13 is placed in larger slots suitably disposed in the stator core 12. The generator I also includes a laminated rotor member 19 mounted on the shaft 10 and having a plurality of axial air passages 29 extending through it. If desired, the axial air passages 29 may also have grooves 21 to increase the surface area exposed to the flow of air. The rotor 19 carries no windings but has teeth 22 on its outer periphery, so that when the rotor is rotated, the reluctance of the magnetic path of the flux produced by the exciting winding 18 is varied, causing a pulsation of the flux to generate a highfrequency alternating current in the stator winding 17. A conical sheet metal baffle 23 is secured to the left-hand end member 4 between the openings 5 and 5, and extends close to the rotor 19 to direct air flowing through the openings 5 and 6 in the desired paths, as explained hereinafter.

The motor 2 is shown as being a more or less usual squirrel-cage induction motor. The motor has a laminated statoi- core 25 which carries the primary winding 26. The core 25 is supported in the frame structure 3 by means of a plurality of radial ribs 27 welded or otherwise suitably secured to the frame structure 3, so that the outer periphery of the core 25 is radially spaced from the frame structure 3. Longitudinal barrier members or baffles 28 are supported on the ribs 27 in the spaces between the core 25 and the frame 3. These barrier members extend'longitudinally? for the entire length of the motor, and extend circumferentially between adjacent ribs 27, so.that the spaces between the core 25 and frame 3 are divided into radially inner and outer longitudinal air ducts 29 and 30, respectively. The motor 2 has a laminated rotor member 31 mounted on the shaft 18 and carrying a suitable secondary winding, shown as a squirrel-cage winding 32. The motor 31 may, if desired, have axial air passages 33 extending through it. A conical sheet metal baffle 34 is secured to the ends of the barrier members 28 at the outside end of the motor and extends close to the end member 4 at that end, as shown, to separate and direct the streams of air flowing through the openings 7 and

8. A similar conical baffle 35 is secured to the other ends of the barrier members 28 adjacent the center of the machine, to direct air flowing through the ducts 29 and 30.

Ventilating air is circulated in separate paths through the motor and generator, through the various air ducts and passages mentioned above, by means of a fan means or blower 36 mounted on the shaft 10 in the center of the machine between the generator and the motor. The fan means 36 consists of a disk member 37 mounted directly on the shaft 10, with a set of fan blades on the generator side for circulating air through the generator, and a second set of fan blades 39 on the motor side for circulating air through the. motor. It will be noted that the baffle 35 extends close to the outside of the fan blades 39 so as to direct air flowing through the inner ducts 29 directly into the fan. The openings 9 in the frame structure 3 are located directly opposite the fan means 36, so that air discharged from both sides of the fan can escape through these openings when the machine is operating as an air-cooled machine, as more fully described hereinafter.

The machine as so far described embodies the basic construction of the new motor-generator set, and all the parts thus far described are common to the machine when used with either air-cooling or water-cooling. Thus, it will be seen that only a single design of the major components of the machine is required for either air-cooled or watercooled operation, and the same basic construction is readily adaptable for either use.

Fig. 1 of the drawings shows the machine arranged for water-cooling. For this purpose a sheet steel housing 40 is secured to the generator end of the machine and a similar housing 4! is secured to the motor end of the machine, the housings 48 and 4 i being placed on the outside of the end members 4. The housing 40 contains a cooling coil 42, which is preferably made of finned copper tubing arranged to cool air flowing over it, and which has end portions 43 extending out of the housing 40 for the entrance and discharge of cooling water. The housing 40 also contains a cylindrical baffle 44, directly under the cooling coil, to cause air entering the housing through the openings 6 to flow through and over the cooling coil 42, and a conical baffle 45 adapted to direct air which has passed over the coil 42 back to the openings 5. Thus, when the housing 43 is in place at the end of the frame 3, over the openings 5 and 6, heated air discharged through the openings 6 will pass over the coil 42 to be cooled thereby and will re-enter the machine through the openings 5. The housing 41, at the motor end, is similar to the housing 40, and contains a cooling coil 46 which may be identical to the coil 42, except that fewer turns may be adequate for sufficiently cooling the air. Baffles 48 and 49, corresponding to the baffles 44 and 45, are also provided in the housing 4 i to direct air entering the housing through the openings 8 over the cooling coil 46 and back into the machine through the openings 7.

Besides the housings 40 and 41, the other additional parts needed for water-cooled operation of the machine include covers 50 closing the openings 9. The covers 50 preferably are provided with a layer of sound-absorbing material 51, of any suitable type, filling the openings 9 to reduce the noise of the machine. A central baffle structure is also provided adjacent the fan means 36. This baffle structure includes a central annular member 52, which extends close to the outer periphery of the fan disk 37, and which carries a conical baffle member 53 on the generator side and a similar baffle 54 on the motor side. A cylindrical baffle 55 is secured to the inner end of the generator rotor i9 and extends close to the fan 36.

In the operation of this machine, when arranged for water-cooling as described above, the air within the frame 3 is circulated in separate paths by the fan means 36 through the generator and motor and the housings 40 and 41, the paths

2,610,992 followed by the air being generally as. shown by the arrows on the drawing. Thus, most of the air discharged from the fan blades 38 on the generator side of the fan is directed by the baffle 53 over the stator winding 17 and into the axial 5 ducts 14 between the generator stator core and the frame and flows longitudinally through these, ducts. Some of the air flows in under the winding 17 and through the air gap between the stator and rotor. The air flowing longitudinally in. this κ way passes through the outer openings 6 in the end member 4 and into the housing 48, where it flows over the cooling coil 42 and is cooled by water circulating through, the coil. After passing over the coil 42, the cooled air is directed by the baffle 45 through the openings 5 back into the frame structure 3, and is directed by the baffle 23 into the axial passages. 20 in the generator rotor i 9. The air flows through these passages, and is directed by the cylindrical baffle 55 back 2 into the fan blades 38 to be recirculated.

The air discharged from the fan blades 39. on the motor side of the fan is directed by the baffles 35 and 54 into the. outer longitudinal ducts 30 on the motor side and flows longitudinally through 2 these ducts, and. through the outer openings 8 in the end member 4 at the motor end of the machine, into the housing 4 i. The air then passes over the coaling coil 46 to be cooled by water circulated through the coil, and is directed by 3 the baffle 49 through the inner openings 7 back into the machine. Part of the air thus entering the: machine flows through the air gap, and through the axial passages 33. in the motor rotor 3(, while the rest of the air flows over the motor primary winding 26 and is directed by the baffle 34 into the inner longitudinal ducts 29. The air thus flowing through the ducts 29 is directed by the baffle 35 back into the fan blades 36 to be recirculated, while the air flowing through the air gap and rotor passages passes directly into the fan. Thus, it will be seen that the air in the machine is circulated in closed, separate paths through the motor and generator, and over the cooling coils in the housings 40 and 41.

When air-cooled operation is desired, the housings 40 and 41, the covers 59, baffles 52, 53 and 54, and the baffle 55 are omitted, as shown in. Fig 2, and a conical baffle 55 is secured to the frame on the generator side of the fan closely adjacent st the openings 9. The baffle 56 extends close to the outer periphery of the generator fan blades. 38. In. the operation of this machine with air-cooling, air enters through the end members 4 at both ends of the machine and is discharged through 5 the openings 9 near the center of the frame, as shown by the arrows in Fig. 2. Thus, the generator is cooled by a. stream of air entering through the inner openings 5 in the end member 4 and directed by the baffle 2.3 into the passages 6 20 in the rotor, and also by a stream of air entering through the outer openings S and flowing through the ducts (4 and over the stator windings (7, and through the air gap. The air flowing through the rotor passages 20 flows directly into 6 the fan 38, while air flowing through the ducts 14 is directed by the baffle 56 over the stator winding 17 and into the fan 38, the air then being discharged radially through the openings 9. The motor is similarly cooled by air entering through 7 the inner openings 7 in the end member 4 and flowing through the air gap and rotor passages, part of the air being directed by the baffle 34 over the primary winding 26 and into the inner longitudinal ducts 92. This air flows through the 1 ducts. 29 and is directed by the baffle 35 over the primary winding 26 at the inner end of the motor and into· the fan 39, which discharges it radially through the openings 9.. Air also flows through the outer openings 8 and the outer longitudinal ducts 3Q to the openings 9 and contributes somewhat to cooling the motor.

It will be seen that both the generator and the motor are. effectively cooled, when the ma) chine is operated with either water-cooling or air-cooling. Effective cooling of the generator is especially necessary in machines of the type illustrated, because of the high-frequency generator currents. In the machine described, it will be 5 noted that incoming cool air flows directly over the. bearing 11 at the generator end and through the ventilating passages 20 in the rotor, thus providing extremely effective cooling for the rotor. This is important in inductor type, alternators 0 because of the very small air gaps used. If the rotor is. not. adequately cooled, the thermal expansion of the rotor may be sufficient to cause it to rub against, the stator. This difficulty is avoided in accordance with the present invention 5 by directing the incoming cool air directly into the rotor air passages so that the rotor temperature rise and thermal expansion are kept small. The square configuration of the generator stator is also an advantageous feature, since it not only 0 provides longitudinal air ducts in a simple and inexpensive, manner, but it allows for some thermal expansion and deformation of the stator core without the risk of damage. Thus, if a conventional cylindrical stator core were pressed > directly into the frame 3, the core would be prevented from expanding radially, and the thermal expansion might be great enough to cause the core to buckle or become distorted and contact the rotor. By the use of a square core, however, ) the stator core is adequately cooled by ths large air ducts and has sufficient, freedom for expansion so that there is no risk of trouble due to thermal expansion.

The construction described makes possible a j motor-generator set which can readily be adapted for either air-cooled or water-cooled operation. It will be seen that the main elements of the machine are the same for either type of operation, and that, the machine can readily be ) adapted for either air-cooling or water-cooling merely by the addition or omission of a relatively few elements during the final assembly of the machine. This construction, therefore, results in a large saving in the cost of manufacture 5 of high-frequency motor-generator sets, since the same design is used for both air-cooled and water-cooled machines, and the problem of stocking parts is greatly reduced because of the smaller number of different parts which must 0 be. maintained in stock, as compared to the number required by the previous practice in which water-cooled and air-cooled machines were built as entirely different machines of unrelated design, with practically no parts in common.

The invention has been described with particular reference to a high-frequency motor-generator set, but it will be apparent that the usefulness. of the invention is not restricted to this particular application, and that it is also appli0 cable to other types of motor-generator sets.

The particular construction and arrangement of the motor and generator and of the cooling means may also be applied to individual dynamoelectic machines, either air-cooled or water’s cooled. It is to be understood, therefore, that

2,610,993 although a specific construction has been shown and described for the purpose of illustration, the invention is not limited to this particular embodiment, but in its broadest aspects, it includes all equivalent embodiments and modifications 5 which come within the scope of the appended claims.