DE2443281A1 - LAMINATED MAGNETIC CORE - Google Patents

Description

DiPL.-ing KLAUS NEUBECKER

4 Dusseldorf 1 ■ Schadowplatz 9

Düsseldorf, 09.09.1974

Westinghouse Electric Corporation,
Pittsburgh, Pennsylvania, V.St.A.

Laminated magnetic core

The invention relates to a laminated magnetic core for alternating current devices, in particular for the stator or rotor of dynamo-electric machines, with at least one winding, and to a method for its production.

Magnetic cores for AC devices and especially for the stators of electric motors are usually layered from metal sheets or lamellas. These lamellas are punched out of electrical steel sheets, then annealed and insulated and then dergeschichten to form the magnetic core to form a laminated core. The windings, usually in the form of coils, are placed in grooves which have been milled into the laminated core or which have already been formed when the lamellas are punched. The material to be removed for the production of the grooves comprises about 25-40% of the total sheet metal cross-section and is lost as waste «. Furthermore, in the case of a layered magnetic core, the choice of the geometric shape of the grooves is limited because of the high cost of the punching tools. Therefore , the achievable copper fill factor is also limited, because the usual methods of winding and inserting the coils into the grooves do not allow sufficient compression. Furthermore, the coils require relatively thick coatings in order to prevent them

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244328 Ί

To protect damage caused by the sharp edges of the slats. Because the conductors are not compressed in current manufacturing processes becomes part of the winding space due to the inherent limitation of a lamellar construction not used. In contrast, the invention is based on the object of providing a laminated magnetic core of the initially introduced to create named type, in which both the space and the material used is better used.

This is achieved according to the invention in that the winding takes the form of a preformed coil with longitudinal and transverse sections End portions is formed that a ground core is formed around the coil and with this forms a unit and that the mass core consists of a large number of micro-lamellae of magnetic material designed as lamellas of the smallest size, which have predetermined magnetic properties and each other and are electrically isolated from the coil.

Such a magnetic core has the advantage that both the conductor arrangement as well as the magnetic core design as a result of the elimination of unused spaces, improved considerably have been.

It is already from US Patents η 1,850,181, 1,669,648 and 1,982,689 known to produce simple toroidal cores by pressing iron * powder particles. However, these toroidal cores have very poor magnetic properties Properties. One reason for this seems to be that it is not possible here to obtain a sufficient iron density achieve. The magnetic properties could accordingly also be improved slightly by the fact that instead of the Iron powder metallic iron in the form of flakes or bits of wire was used. The metallic flakes passed made of molten iron that was sprayed in powder form and then rolled around elongated flat metal particles to obtain. However, this did not result in any appreciable improvement in the magnetic properties.

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Advantageous refinements of the invention emerge from the subclaims. In the following the invention is based on a In the accompanying drawing illustrated embodiment illustrated in more detail, with further features, embodiments and advantages of the invention. In the drawing show:

Fig. 1 is a view of a preformed stator coil with partially removed insulation, which is in the magnetic core can be used according to the invention,

Fig. 2 shows a vertical cross section through a filled container for the production of the magnetic core according to the invention,

Fig. 3 shows a cross section along the line III-III of Fig. 2,

4 shows a diagram of the applied voltage as a function of the no-load current,

5 shows a diagram of the dependence of the applied voltage on the no-load power and

6 shows a macro photograph of the coil cross-section after application of pressure and deformation with the mass core a closed unit.

The basic material of the magnetic core according to the invention consists of small, essentially rectangular cuboids made of magnetic material Material commonly referred to as "micro-lamellar" will. The magnetic material is preferably a low carbon one Steel, such as that commonly used in tin cans, is abundant and relatively cheap. Of course it can any other ferromagnetic material which can be brought into substantially the same shape can also be used. That The material preferred here is obtained as so-called black plate, i.e. in the state before tinning, as it is for the manufacture

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Position of tin cans is made. This material is available in a wide range of thicknesses, usually in the range between 0.13 and 0.36 mm. It seems that Magnetic core according to the invention to give a relatively large range for the particle size satisfactory results, however The microlollars should expediently have a length between 1.27 and 1.52 mm, a width between 0.25 and 0.51 mm and a thickness between 0.13 and 0.36 mm. The micro lamellas can be manufactured with these dimensions from the sheet metal can pre-material by exposing it with a milling cutter high speed is shredded or first slit to the desired width and then with a milling cutter against a stationary cutting edge is cut. In the latter case, the slitter and cutter are aligned one behind the other.

Other starting materials can be used with equally good results can be used, for example steel wool and scrap and ingot shavings. In special engines, for example for aircraft , cobalt iron scrap can also be processed into micro-lamellas.

During the production of the micro-lamellas in the manner described, the material is subjected to considerable mechanical stress. Since that If material is to be used in a magnetic core, favorable magnetic properties must be achieved again. To do this you have to the stresses imparted to the steel during the manufacture of the micro-lamellas are released again. Treatment is also carried out by decarburizing and deoxidizing so that a magnetic core structure of high density or high fill factor is achieved which also has excellent magnetic properties. When working out the magnetic properties The micro-lamellae are expediently annealed at temperatures between approximately 700 and 800 C. These temperatures are sufficient to release the tensions generated in the micro-lamellas during their manufacture.

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To decarbonize the micro-strips, the heat treatment begins In the specified temperature range, an environment with wet hydrogen is used, which has a dew point above is around 16 ° C. The wet hydrogen environment can reduce the carbon content to a value below approximately 0.01 percent by weight to reduce »This hydrogen environment is maintained over the heated micro-lamellas for a period of up to two hours until the desired low Carbon content is reached »Then the annealing is within the specified temperature range in a dry hydrogen atmosphere, which is able to deoxidize the micro-lamellae. It has been found that forming gas and other strongly oxidizing environments that produce oxides on the steel cannot be used because of the thickness of the oxide layer adversely affects the iron fill factor and thereby the final magnetic properties of the finished magnetic core accordingly deteriorated. The dry hydrogen environment will have a dew point less than approximately Maintain -40 ° C for a period of approximately two hours. Then the micro-lamellas are placed under the Protective gas cooled to room temperature.

In order to achieve low losses in the finished magnetic core, the micro-lamellae must be electrically isolated from one another. For this purpose, treatment with magnesium methylate has proven to be particularly beneficial in order to produce an insulating layer on the lamellae, because such an insulating layer is very thin and flexible enough to withstand the pressures that occur during molding. It can be used although also other insulating layers _f but causes this layer so that the finished magnet core has a sufficient resistance between the laminations, low core losses and other favorable magnetic properties.

The method according to the invention can be used for the production of any Magnetic cores are used, and other techniques are also used

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accessible / like the so-called "free forming" or the so-called "fixed forming ^1. However, the following description relates specifically to a method for forming stators with embedded windings, although the method is equally applicable to both static and dynamic electrical devices is where electrical conductors are cast into a magnetic core.

The invention is described here with reference to the manufacture of the stator of an electric motor. In Fig. 1 is a prefabricated Stator coil 10 shown, which has a number of vertically extending longitudinal sections 12, which in the previous Known methods produced electric motors would run in the grooves of the stator. The longitudinal sections 12 are connected to one another by transverse end sections 14. The stator coil 10 is expediently on a winding form manufactured. It is usually made of an electrical conductor wire, so-called magnet wire, and provided with a further insulation layer 16 made of plastic or the like. The insulation layer 16 should have a thickness not exceeding approximately 76 micrometers and the shape of the stator coil Keep 10 when removed from the form.

In Fig. 2, a container 20 is shown, which has a bottom 22 and upwardly extending side walls 24, which with the bottom 22 are in one piece. The container 20 is made of resiliently flexible polyurethane that is cast in the desired shape has been. However, natural rubber, silicone rubber and synthetic elastomers can also be used for the container 20. On the bottom 22 of the container 20 sits within the side walls 24, a plastic bottom 26, which has a in its center has opening 28 for receiving a dome 30 in the middle of the container 20 is arranged and serves to define the opening of the stator for receiving the rotor. The plastic floor 26 furthermore has an annular opening 32 which is used to receive the end sections 14 of the prefabricated stator coil 10

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serves.

Fig. 3 shows in cross section, like the side walls 24, the longitudinal sections 12 of the stator coil 10 and the mandrel 30 are arranged to one another. In this arrangement there is a predetermined amount of the annealed and isolated micro-lamellas into the spaces 34 and 35 filled between the side walls 24, the mandrel 30 and the longitudinal sections 12. While filling the Vibratory energy is applied to the container 20 and its contents in order to close the micro-lamella as closely as possible pack. In order to give the magnetic field a preferred direction, the stator coil 10 can be used when filling the micro-lamellae and, if necessary are still afterwards excited by an electrical power source, so that the micro-lamellae along the magnetic Align lines of flux and form poles that are particularly strong cause magnetic interaction with the shape of the coil.

When a sufficient amount of micro-lamellae have been filled into the spaces 34 and 35, a tight fit will be made Cover 36, which is essentially a mirror image of the plastic base 26, on the micro-lamellas, the end sections the stator coil 10 and the mandrel 30 placed on top »The container 20 filled in this way can then be used to solidify the micro-lamellae Are exposed to pressure;

In order to solidify the micro-fins uniformly around the stator coil 10, subject the assembly to isostatic pressure. Such an isostatic pressure is capable of both the longitudinal sections 12 of the stator coil 10 and the micro-lamellae condense. Since the container 20 is made of a flexible material, it allows dimensional changes when pressure is applied, so that a packing factor of over 80% can be achieved.

For the compression, the filled container 20 is in an isostatic Introduced pressure chamber, which then with a liquid

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speed is filled and pressurized sufficiently to compress the micro-lamellae and the stator coil accordingly to achieve, so that their packing density is greater than 80% of that occupied by the micro-lamellae and the conductors embedded therein Volume is. The amount of pressure going beyond a certain limit is not very critical, it has

2, however, it has been found that the application of about 3.5 t / cm is certain to give a stator core which has the desired Has a packing factor of more than 80%.

As an example, the following is the production of a two-pole induction motor can be described with three quarters of a horsepower, which is suitable for two voltages. It is described in the Manner made in a winding form of a stator coil 10. After removing it from the form, it is treated in a bath, which is obtained by liquefying a dry plastic powder of the polyglycidyl ester of a dihydrophenol. Through this a very hard but flexible electrical insulation layer is created on the longitudinal sections and on the end sections of the stator coil upset.

This coil is now made in the manner described together with a mandrel 30 made of steel in the flexible container 20 Polyurethane is used and, together with the micro-lamellas, exposed to a hydrostatic pressure of 3.5 t / cm.

A three-quarter horsepower induction motor equipped with such a cast stator gave those shown in FIGS Test results. Figure 4 is a plot of applied voltage versus open circuit current for both one motor wound in the usual way with a core package of punched lamellas as well as for a motor with a magnetic core according to the invention. FIG. 4 shows the improvement brought about by the use of micro-lamellae and one together with them in a uniform stator core molded preformed stator coil is achieved. For all tensions in the range between

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120 and 240 V is the no-load current for the cast stator core according to the invention smaller.

Fig. 5 shows the dependence of the applied voltage on Idle power for a cast stator core motor and a common motor. Here, too, it can be clearly seen that a stator according to the invention provides a very considerable improvement over a conventionally manufactured motor " At 220 volts, the 120 watts of the motor according to the invention represent a 30% reduction over the 170 watts of the conventional motor of idle power. This improvement is attributed to the higher overall density obtained with the process is to be achieved according to the invention.

Fig. 6 is a macro photograph of the cross section of a longitudinal portion 12 of the stator coil 10 after application of the hydrostatic pressure. As can be seen, the lead wires are the Longitudinal section through the mere application of the hydrostatic

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Pressure of about 3.5 t / cm so that they form essentially regular hexagons over the entire cross-section be used to work. Although the copper fill factor almost reaches 100%, neither the wires nor their insulation have been damaged in any way. The insulation between the wires withstood 800 V and the insulation between the wires and the micro-lamellas even 2600 V. In this way, the individual conductor wires of the longitudinal sections remain completely separate from one another despite the application of the hydrostatic pressure.

Another advantage of the compression of the micro-lamellas and the Conductor wires in a unitary magnetic core means that harmful vibrations between the insulated windings

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and the lamellae can be reduced quite considerably because of their almost complete solidification. This way damage will be avoided the electrical insulation by grinding or by cutting the insulation on the conductor wires almost completely avoided.

In order to evaluate the magnetic properties, the conductor wires were used in a magnetic core produced as described above drilled out and the core examined for its magnetic behavior. Density measurements showed that the micro-lamellae compressed to a packing factor of approximately 89% had been. The magnetic core had a magnetic induction of 12.5 kilogauss when the applied magnetic field was 50 oersteds, and 14.2 kilogauss with a magnetic field of IQO Oersted. at 15 kilogauss, the iron losses were 13 watts per kilogram. These properties are considerably better than those of laminated ones Magnetic cores.

In the above, the application of the hydrostatic Pressure of a liquid is described, but other methods can also be used, for example isostatic Compaction technique with the help of a dry bag. Furthermore, there are usually no special ones for the micro-lamellas Binder required. If strong centrifugal forces occur or if lower isostatic pressures are used, however, a binder would be beneficial. An excellent binder is potassium silicate in an aqueous medium, the excellent Results achieved. If a binder is used, it must be able to exert its binding effect without the magnetic one To give particles an excessive thickness, which would lower the packing density of the magnetic material itself. The binders commonly used with iron powder, for example, such as carbowax and organic synthetic resins, are for this unusable because their layer thickness is too great and results in too great a reduction in the packing density.

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In the event that the use of a magnetic core with molded Micro-lamellas in the finished stator arrangement are too high Reluctance results, it may be necessary on one of the previously described manner to apply ground core to reduce the reluctance a wound yoke, for example Wind a tape of magnetic material on the outside of the earth core.

In practice, this is done by wrapping a thin strip of magnetic material around a cylinder tube and inserting it first into the Pressure transferred container used. This is followed, as before, by the stator coil, the mandrel and then the one between the belt cylinder and microla larvae filled into the mandrel. Through compression by means of a pressurized liquid, the entire arrangement is then combined to form a unitary magnetic core.

From the foregoing it can be seen that considerable savings are made in terms of both the conductor wires and the magnetic core can be achieved because practically all air gaps are eliminated and a higher material density is achieved than when using of layered lamellas and then applied windings as in a conventional motor. In addition to the Savings in material and labor is achieved an improved performance, which consists in that at substantially Reduced input powers deliver greater powers or, conversely, with the same input powers, greater output powers are emitted.

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Claims (12)

Patent claims: 1. Laminated magnetic core for AC devices, in particular for the stator or rotor of dynamo-electric machines, with at least one winding, characterized in that the winding is a preformed coil (10) with longitudinal sections (12) and transverse end portions (14) is formed that a ground core is formed around the coil (10) and with this forms a unit and that the mass core consists of a large number of micro-cells designed as lamellae of the smallest size magnetic material, which have predetermined magnetic properties and each other and are electrically isolated from the coil (10). 2. Magnetic core according to claim 1, characterized in that the mass core in addition to the micro-lamellae Contains binding agent. 3. Magnetic core according to claim 1 or 2, characterized in that the micro-lamellae are essentially elongated with rectangular cross-section and approximately a length between 1.27 and 1.52 mm, a Have a width between 0.25 and 0.51 mm and a thickness between 0.13 and 0.36 mm. 4. Magnetic core according to one of claims 1 to 3, characterized in that the insulation (16) of the Coil (10) opposite the micro-lamellas is no thicker than approximately 76 micrometers. 5. Magnetic core according to one of claims 1 to 4, characterized in that one enclosing the ground core Yoke is provided, which is used as a Bendwickel- 50981 2/0820 Toroidal core or is designed as a package of a large number of stamped lamellae. -. "-" ■■ '.. 6. A method for producing a laminated magnetic core according to any one of claims 1 to 5, characterized in that the micro-lamellae made of a ferromagnetic material , preferably from a low-carbon steel, are annealed to decarbonize, deoxidize and improve their magnetic properties and are electrically insulating be provided with a coating. 7. The method according to claim 6, characterized in that the coil (10) already with the desired Final dimensions preformed and, preferably centric, is inserted into a flexible container (20) of predetermined shape that a predetermined amount of the micro-lamellas around the coil (10) is filled into the container (20) and the container (20) is closed so that the Micro-lamellas around the coil (10) up to a degree of compression are compressed by more than 80% and that the compressive pressure is removed and the mass core from the container (20) is taken. 8. The method according to claim 7, characterized in that the micro-lamellae prior to pressing with a Binder treated and / or coated. 9. The method according to claim 6 or 7, characterized in that g e k e η η, that a mandrel (30) of predetermined shape in the container (20) before the micro-lamellas are filled is used at a predetermined distance within the coil (10). 10. The method according to any one of claims 7 to 9, characterized in that the container (20) when Filling the micro-lamellas vibrational energy is supplied. 509812/0820 11. The method according to any one of claims 7 to 10, characterized characterized in that the coil (10) when Pressing, preferably already when filling the micro-lamellae, is excited. 12. The method according to any one of claims 7 to 11, for production a laminated stator core, characterized in that a prefabricated stator yoke is inserted into the container (20) before the coil (10) is inserted the dimensions of the finished stator is used. 509812/0820