GB2288077A

GB2288077A - A method for producing a component which includes a winding and which component is intended for use in an electric machine

Info

Publication number: GB2288077A
Application number: GB9506098A
Authority: GB
Inventors: Ing Harald Neudorfer
Original assignee: ABB Verkehrstechnik GmbH
Current assignee: ABB Verkehrstechnik GmbH
Priority date: 1994-03-31
Filing date: 1995-03-24
Publication date: 1995-10-04
Anticipated expiration: 2015-03-24
Also published as: NL194690C; AT406210B; ATA69194A; NL9500593A; GB9506098D0; ES2109868A1; DE19505866C2; AT406210B9; NL194690B; GB2288077B; ES2109868B1; DE19505866A1

Description

1 - 2288077 The present invention relates to a method for producing a

component which includes a winding and which component is intended to be used in an electric machine. The invention also relates to a component made by said method and to an electric machine including such a component.

The production of windings is a very expensive and laborious operation; more particularly problems of vibration and oscillation may occur with the rotor windings, due to the large number of winding elements introduced into or applied to the base member of the rotor and their manufacturing and assembly tolerances. Even af ter-proces sing, with the further increase in expenditure of time and labour, cannot obviate these problems with conventionally produced windings.

A special application which can be mentioned is asynchronous motors, either outside-rotor or insiderotor ones, whose shortcircuit winding consists mainly of longitudinally extending rods in grooves in the rotor casing or on the rotor shaft, and a coaxial ring at each end of the rod arrangement which connects the rods to one another - i.e., short-circuits the rods. The material preferably selected for the rods and shortcircuit rings is copper, and by the conventional manufacturing method the rods and rings are produced separately and suitably prepared, whereafter the rods are inserted into pre-formed and if necessary after- processed grooves in the rotor casing or on the rotor shaft, axially secured, for example, wedged over and soldered with the rings applied thereafter. No matter how well the rods are prepared and the grooves machined, at places there are gaps between the grooves and rods and also between the rotor casing or rotor shaft and the shortcircuit rings, and these may lead to considerable problems of vibration and oscillation, more particularly in the case of rapid- in 2 - ly operating machines.

An object of at least preferred embodiments of the present invention is to reduce the probability of the aforementioned vibrations and oscillations occurring.

This object is achieved by the features set forth in the Claims hereto.

In one preferred embodiment, at least some winding portions are cast and at least a portion of the casting mould is formed by the part of the machine, preferably the rotor or parts of the rotor, which receives the winding, both the substantially longitudinally extending winding portions and also the winding portions connecting the latter being cast, preferably in one casting operation. During the casting of the winding portions onto the machine part, its recesses, which are intended to receive said winding portions and as a result form at least a portion of the surface of the casting mould for said portions, are completely filled up, irrespective of whether the surfaces are unmachined or after-machined.

In this way gaps are inhibited, manufacturing tolerances are compensated, and as a result the winding portions are reasonably securely and reliably seated. The secure seating also inhibits movements of the winding portions in relation to one another and the machine which lead to vibrations and undesirable oscillations. This is more particularly important for the very rapidly running rotors, and in machines such as frequency converters. Since all the surface structures are filled by casting, for example, in the case of a solid steel or cast steel rotor without further machining of the inner surface, in these kinds of rotor, also the problems of vibration and oscillation can be reduced without any expensive afterprocessing of the rotor surfaces. As a result, manufacturing costs and overall expenditure can be appreciably reduced.

AICA According to an advantageous variant of the process according to the invention, the winding portions are cast higher and thicker than corresponding to the required height or thickness and are after-processed following the casting operation, preferably by cold shaping, preferably by rolling. At the same time, reserves are still available for the accurate production of the winding portions, and if necessary the whole surface of the winding and of the machine part bearing the winding can be brought precisely to the identical required dimension. The winding portions can also be after-machined together with the machine part bearing the windings following the casting process. The variant disclosed in the foregoing paragraph has also the advantage of enabling the cast winding portions to be advantageously after-processed by cold shaping, preferably by rolling, to eliminate any air gaps and cavities between the rotor and the winding which may have occurred due to shrinkage during the cooling of the cast material. After cold shaping, or as an alternative thereto, the cast winding portions can be provided to the height of the teeth of the machine, preferably of the rotor, by further after-processing, preferably by turning. 25 If the component, preferably the rotor, bearing the cast winding or the cast winding portion takes the form of a solid steel or cast steel part, the result is a construction which is insensitive to the high temperatures of casting and is therefore less expensive. 30 On the other hand, in another variant of the invention the component preferably the rotor, bearing at least one of the windings takes the form of a tin-plated part of refractory coated, preferably enamelled phosphated metal sheets, and at least that the winding portions situated outside the tin-plated zone are cast on. This 0 4 - kind of construction results in improved magnetic properties of the electric machine, clear improvements in vibrational and oscillatory behaviour being already achieved in comparison with conventional tin- plated machines by the casting of at least portions of the winding. Advantageously the winding portions, extending substantially in the longitudinal direction of the machine, are prefabricated and introduced into grooves in the machine, whereafter the shortcircuiting rings are cast which connect the longitudinally extending winding portions. This variant relates more particularly to conventional tin-plated machines whose lacquer- insulated sheets cannot withstand the high temperatures such as occur when the winding material is cast in. The hot cast-in material (e.g. copper with a melting point of 10890C) does not contact the lacquer insulation, which therefore remains undamaged. Nevertheless, the winding is applied clearance-free in the zone of the connection of the cast and prefabricated portions and also of the cast portions of the winding on their own, the result being a substantial improvement in the vibrational and oscillatory behaviour of the machine.

The portions extending longitudinally of the machine, as defined in the previous paragraph, can be oriented precisely axis-parallel or else enclose a certain angle with the longitudinal axis - i.e., be inclined. In the conventional manufacturing technique, with the longitudinally extending winding portions in the form of prefabricated rods, the inclined construc- tion represents a variant which is very expensive to produce, mainly due to the inclined protection of the rods, resulting in a soldering gap of variable width and therefore requiring to be removed at additional expense. With casting these disadvantages do not occur, so that casting is very suitable for machines having inclined 1 p d-- 1 winding portions.

If, according to a further feature of the invention, the part preferably the rotor, bearing at least one of the windings takes the form of a tinplated part of refractory coated, preferably enamelled phosphated metal sheets, and at least that the winding portions situated outside the tinplated zone are cast on, a construction is less sensitive to elevated temperatures. Since they also have better magnetic properties than solid steel machine parts, the cast winding portions can be increased in number or size, thus also even further improving the vibrational and oscillatory behaviour.

Due to their high temperature resistance, machine parts made from sheets having a high temperature resistant coating and solid steel machine parts advantageously even the whole winding can be produced in one piece as a casting, so that the best magnetic properties are combined with optimum vibrational and oscillatory behaviour. According to a further variant of the invention both the substantially longitudinally extending winding portions and the winding portions connecting the latter can be cast, preferably in one casting operation. The result is a one piece winding whose whole contact surface with the machine part, particularly the rotor, bearing the winding is clearance-free and constructed congruently to compensate all tolerances and surface structures. By this variant of the process, therefore, a machine can be produced in which problems of vibration and oscillation are reduced. For example, in the case of both solid steel and cast steel machine parts without after-processing, for instance, for the grooves in rotors, manufacturing expenditure is reduced and therefore time and money saved - in the casting of the whole rotor winding a 50 to 60% saving is possible for the costs of the winding. This variant of the process can ALI also be used with the same effects and advantages for plated machines of, for example, enamelled or phosphated sheets, which withstand substantially higher temperatures than lacquered sheets.

Preferably, the machine according to the invention is an electric motor, more particularly an asynchronous motor, in which the rotor winding is at least partially cast, to improve oscillatory and vibrational behaviour. This has a particularly advantageous effect on an out- side-rotor asynchronous motor having a cast shortcircuit winding rotating very rapidly around the inside stator.

k -1 - 7 For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings, in which:- Fig. 1 is a cross-section through the rotor casing of an outside-rotor motor; Fig. 2 is a longitudinal section through the casing of Fig. 1, taken along the line A-A of Fig. 1 but with the winding inserted; Fig. 3 is a detail of the internal surface of a rotor, taken along the line B-B in Fig. 2; Fig. 4 is a detail, corresponding to Fig. 3, of a variant; Fig. 5a shows an inside rotor with inserted windings, different variants being shown together in one is figure; Fig. 5b shows a detail at the outer end of the shortcircuit winding of the rotor of Fig. Sa; Fig. 6 is a detail of the rotor of Fig. 5a, in cross-section along the line C-C in Fig. Sa; Fig. 7 is a cross-section corresponding to Fig. 6, but with a somewhat different rotor construction; Figs. 8a and 8b show respectively an internal plan view of one half of an outside-rotor motor having axis parallel and inclined cast winding portions respective- ly; and Figs. ga and 9b are side views of an inside rotor, also with axisparallel and inclined cast winding portions respectively.

Fig. 1 shows diagrammatically the construction of an outside-rotor motor casing 1, whose inner surface is formed with teeth 2 and grooves 3. Substantially longitudinally extending winding portions (often referred to as "rods") of the preferably copper winding, in asynchronous motors the shortcircuit winding, are inserted in the grooves 3 between the teeth 2 spaced out at equal Arl- intervals along the internal periphery of the casing 1.

The substantially longitudinally extending winding portions 4 are shown in Fig. 2. At both ends each of the substantially longitudinally extending winding portions 4 is connected via winding portions 5 extending along the inner periphery of the casing 1 to at least one other winding portion, in the case of asynchronous motors to all the other substantially longitudinally winding portions, to form the shortcircuit winding. In the last-mentioned case the winding portions 5 form the two short- circuiting rings of the rotor. In the further course of the description the invention will be explained with reference to the preferred embodiment of an asynchronous motor, although this represents no limitation, and the invention can be applied to any electric machine having windings.

As shown in the upper part of Fig. 2, the plane of the section extends inside one of the grooves 3, thus clearly showing the one-piece construction, obtained by the casting of the shortcircuit winding, of the substantially longitudinally extending winding portions 4 with the adjoining shortcircuit rings 5. As shown in the lower part of Fig. 2, the plane of the section is at the height of a tooth 2; it can be seen how the thickness of the winding portions 4 and the shortcircuit rings 5 preferably correspond to the height of the teeth 2. This can be done by a suitable design of the casting mould, or by the after-processing of the inside of the rotor, for example, by turning to the required dimen- sions.

Fig. 3 shows how the material of the winding portions 4 completely fill the grooves 2 and also completely penetrate into the lower corners. With the after-processed solid steel or cast steel rotors having substantially the groove shape shown in Fig. 3, such a Arl complete filling of the grooves can be achieved, if at all, only at high, economically unjustifiable expense. Consequently, with conventional rotor constructions the rods can always move in the grooves, the result being undesirable and even dangerous oscillations or vibrations, more particularly with rapid rotation. These effects are inhibited by the invention's complete filling of the grooves 3 by the winding portions 4.

Plated rotors'also have a cross-sectional construc- tion corresponding to Fig. 3. Even when prefabricated rods are inserted in the form of axis-parallel winding portions, so as not to damage the insulation between the sheets by the high temperatures occurring during the casting of the windings, oscillatory and vibrational behaviour can be improved and manufacture simplified by casting the shortcircuit rings 5 on the rods and applying the rings 5 in an optimum manner to the inner surface of the rotor casing 1.

Plated rotors of phosphated or enamelled sheets can even contain completely cast - i.e., one piece windings, since such sheets are insulated from one another by their surface treatment, and the insulation survives relatively high temperatures without damage.

Even in the case of unprocessed cast steel rotors, the inexpensive casting of the winding portions 4 can ensure that they completely fill the relatively irregularly shaped grooves 3. Such a clearance-free fit of the winding in the rotor is impossible by conventional processes without laborious and expensive after- processing.

Fig. 4 shows a detail corresponding to Fig. 3, namely the not yet afterprocessed inside of an unprocessed cast steel rotor with cast-in winding portions 4. Preferably the teeth 2 and if necessary the winding portions 4 also are turned down to the height of the An 11ne E.

Since the cast-in material for the winding portions shrinks during cooling, air gaps may however occur in the lower zone of the grooves 3 and between the shortcircuit ring 5 and the rotor 2, 6. The gaps are advantageously eliminated by a cold shaping of the cast material, preferably in at least one rolling operation, if necessary a number of rotations of the rotor in contact with a roller.

As can be seen from Figs. 5 to 7, the process and construction according to the invention can also be used for inside-rotor motors.

Fig. 5a is a longitudinal section through an inside-rotor motor, showing in one drawing different variants of the precise arrangement of the winding portions and the design of the shortoircuit ring. The drawing again shows the substantially longitudinally extending portions 4 of the shortcircuit winding and the shortcircuit ring 5; in conventionally plated machines the winding portions 4 can again consist of prefabrica- ted rods. The winding is disposed on a solid steel or cast steel part 6 which is attached to a shaft 7 or has corresponding stub shafts. Advantageously vanes 8 are provided for the ventilation and cooling of the machine.

As shown on the left in Fig. 5a, the shortcircuit ring 5 can extend radially a short distance in the direction of the shaft 7 or, as shown on the right in Fig. 5a, can be constructed to be aligned by its inner periphery with the inner end of the grooves 3. For reinforcement the steel part 6, as shown in the detail in Fig. 5b, can be axially lengthened and engage around the shortcircuiting ring 5 in the form of a shrunk ring 11.

The grooves 3 of the inside rotor can take the form of outwardly open or semi-open grooves; in the latter I; Z 11 - case, to retain the winding portions 4, the teeth 2 have portions 9 (see Fig. 6) which project on both sides and bound the groove opening on the outside. In this embodiment during casting, preferably centrifugal casting, the groove opening is covered by the application of a binding.

However, instead of the open grooves 3, as shown at the bottom of Fig. 5a and in Fig. 7 the steel part 6 can be formed along its outer periphery with substantially longitudinally extending bores 10 for receiving the winding portions 4.

It is possible to construct the part 6 in the form of a plated part receiving the winding in the case of an inside rotor also, the arguments set forth hereinbefore in connection with plated outside rotors apply accordingly.

The casting of the windings or at least of portions thereof is particularly advantageous if machines having inclined winding portions are to be made, in which the obliquely projecting ends of the conventional prefabricated rods represent a heavy additional manufacturing cost. According to the invention outside-rotor motors can be more simply and rapidly produced with both substantially precisely axis-parallel, longitudinally extending winding portions (as shown in Fig. 8a) and also with inclined constructions (as shown in Fig. 8b). Of course, this applies equally well to inside-rotor motors, in which also windings having substantially precisely longitudinally extending portions (Fig. 9a) and inclined rotors (as shown in Fig. 9b) can be in a similar way more simply and rapidly produced than by the conventional production techniques.

In completion, it should also be pointed out that due to the additives necessary or advantages for casting, cast copper has lower conductivity than elec- 1 9^ OLA trolyte copper, for example, before prefabricated rods as axis-parallel winding portions or shortcircuiting rings. However, this disadvantage can readily be counteracted by suitably increasing the cross-section of the cast winding portions, so that the advantages of much cheaper manufacture, with up to 60% savings in rotor winding production per machine, including substantially improved oscillatory and vibrational behaviour, heavily predominate.

r - 13

Claims

1. A method for producing a component which incorporates a winding and which component is intended to be used in an electric machine, which method includes the step of casting at least a portion of said winding.

2. A method according to Claim 1, wherein said winding comprises rods and shortcircuit members, and wherein said method comprises the step of casting at least a part of one of said rods and/or one of said shortcircuit members.

3. A method according to Claim 2, wherein said rods and said shortcircuit members are formed during the same casting operation.

4. A method according to Claim 2, wherein said rods 15 are prefabricated and said shortcircuit members are cast in situ.

5. A method according to Claim 1, 2 or 3, wherein said winding is cast in situ.

6. A method according to any preceding Claim, includ20 ing the step of cold shaping at least a portion of said cast portion of said winding.

7. A method according to Claim 6, wherein said cold shaping comprises cold rolling.

8. A method according to any preceding Claim, includ- ing the step of removing surplus cast material.

9. A component when made by a method according to any preceding Claim.

10. A component as claimed in Claim 9, including a steel body which supports said winding and which is itself cast.

11. A component as claimed in Claim 9, including a steel body which is formed from the solid and which supports said winding.

12. A component as claimed in Claim 9, including a body 35 having a temperature sensitive portion, wherein those on- - 14 portions of said winding which overlie said temperature sensitive portions are prefabricated and those portions of said winding which overlie parts of said body which are not temperature sensitive are cast in situ.

13. A component as claimed in Claim 12, wherein said temperature sensitive portion of said body is plated.

14. A component as claimed in Claim 13, wherein said temperature sensitive portion of said body is plated with a refractory coating.

15. A component as claimed in any of Claims 9 to 14, comprising a rotor.

16. An electric machine comprising a component as claimed in any of Claims 9 to 15.

17. An asynchronous motor comprising a component as claimed in any of Claims 9 to 15.

Y f