EP0557549A1 - Toroidal core transformer - Google Patents

Abstract

Transformers manufactured using transformer laminates having a preferred magnetic direction are heavy, have a large volume and are difficult and thus uneconomic to manufacture. The invention specifies a toroidal core transformer having a circular toroidal core which is wound in the preferred magnetic direction, does not have these disadvantages and can be manufactured simply and thus in an economical manner. <IMAGE>

Description

The invention relates to a method for producing a cast power resin cast with a wound cutting tape core, preferably made of a cold-rolled ferro alloy, which has a magnetic preferential direction, and a toroidal transformer produced by this method.

Modern ferro alloys for the production of transformer sheets, consisting essentially of iron / nickel or iron / silicon alloys, have very good magnetic properties which make it possible to construct transformers with correspondingly good electrical values, but are very difficult to process. Shall the good magnetic Properties of these transformer sheets are exploited, the magnetic preferred direction with the main flow direction in the transformer sheet must match as much as possible. This means that, for example, normal M-cuts cannot be used, but that with a three-column transformer, the preferred magnetic direction in the yokes must be perpendicular to that in the cores. In addition, the core and yoke sheets must be mitred to largely keep the flow direction in the preferred direction of the sheets. Cutting the sheets with a special sheet metal cutting machine with angled cutting device, as well as, in particular, the necessary, careful layering of the transformer sheets, is extremely time-consuming and cost-intensive. This means that transformers constructed with these transformer sheets have satisfactory electrical properties, but are relatively expensive. Added to this is the large volume and weight of such transformers in conventional sheet metal cuts, which can lead to difficulties in their installation.

Toroidal transformers have been known for a long time, in which the transformer sheet, which is in tape form, is wound in a ring and then this toroid is wound with transformer coils. With such a toroidal transformer, the difficulties described above do not arise, since the direction of flow in the transformer sheet always corresponds to its preferred magnetic direction. Difficulties arise with such toroidal transformers due to the application of the windings special special winding machines. Toroidal transformers and chokes have therefore so far only been built for small outputs. Grid power transformers with this structure have not yet been disclosed.

Starting from these toroidal core transformers or toroidal core chokes, cutting band cores are also used which, like the toroidal core transformers, have a wound core, but usually wound in an approximate rectangular shape, which is cut at two points transversely to the longitudinal direction of the metal sheets. This makes it possible to place previously manufactured spools on the straight parts of these cut ribbon cores wound in a rectangular shape and then to bring the two core halves together again with the smallest possible air gap. This eliminates the difficulty of winding such cores, which also have extremely good electrical properties. However, only low-power transformers equipped with such cutting tape cores have so far become known.

• 1. Beschichten des Ringkerns mit einer elektrisch isolierenden, jedoch wärmeleitfähigen und wärmebeständigen, elastisch-nachgiebigen Dämmstofflage;
• 2. Zerschneiden des Ringkerns in zwei Ringhälften;
• 3.
  • a) Überschieben einer Niederspannungs-Rechteckwicklung aus lackisoliertem Rund-, Rechteck- oder Profildraht auf jeweils eine Ringhälfte;
  • b) gegebenenfalls Überschieben einer oder weiterer Rechteckwicklungen auf die jeweils zuvor aufgebrachte Wicklung;
• 4.
  • a) Vergießen der bewickelten Ringkernhälften oder
  • b) Aufbringen von aus Gießharz gefertigten Stützelementen;
• 5. Überschieben von jeweils zusammengefügten Hochspannungs-Wicklungsscheiben;
• 6. Zusammenfügen der beiden Ringkernhälften;
• 7. Verbinden oder Herausführen der Wicklungsenden;
• 8. Vergießen des kompletten Transformators mit rippenartigem Umgießen der Wicklungsscheiben.

The object of the invention is to utilize the good properties of such toroidal transformers with ribbon cores also for transformers and chokes of relatively high power, so that they can also be used to build network power transformers with such cores. This is achieved in the manner according to the invention, starting from a strip which is spirally wound in the preferred magnetic direction and which has been solidified by adding resin to form a round toroidal core by the following, partially known process steps:

• 1. Coating the toroidal core with an electrically insulating, but heat-conductive and heat-resistant, resilient insulation layer;
• 2. Cut the toroid into two halves;
• 3rd
  • a) pushing a low-voltage rectangular winding made of enamelled round, rectangular or profile wire onto one half of the ring;
  • b) if necessary, pushing one or more rectangular windings onto the respective previously applied winding;
• 4th
  • a) casting the wound toroid halves or
  • b) applying supporting elements made of cast resin;
• 5. Pushing over each of the assembled high-voltage winding disks;
• 6. Join the two toroid halves;
• 7. Connect or lead out the winding ends;
• 8. Casting the complete transformer with rib-like casting around the winding disks.

The toroidal transformer according to the invention thus differs from the known toroidal transformers with a ribbon core in that it does not have a rectangular wound core like this, but this winding core is circular. This has the disadvantage, ostensibly, that no cylindrical coils can be pushed onto the winding core, but that, and that probably prevented the experts from using such round winding cores, the winding and sliding on of the coils could be difficult. In fact this is not the case, if so, as by the Invention is set forth, since the low-voltage coil with its relatively thick wire cross-section pre-wound as an air coil and then can be pushed over the half-arch of the cut core without difficulty. Also, as practice has shown, pushing additional low-voltage windings over the respective previously applied winding presents absolutely no difficulties, so that the previous objection to toroidal transformers with a round-wound toroid is refuted. However, the high-voltage coils cannot be pushed on in this way. This high-voltage winding would actually have to be wound in a semicircle, which in turn would require a special winding machine. In addition, insulation problems could arise with such a high-voltage coil. These difficulties are avoided according to the invention in that the high-voltage coil is divided into individual, relatively thin winding disks, which can now be wound without difficulty on normal winding machines and can also be easily pushed onto the ring core previously cast or provided with support elements. In this case, the winding disks should not exceed a disk width of 40 degrees of arc of the inner ring core diameter, in particular to enable the individual winding disks to be pushed over the ring core. The disc-shaped design of the high-voltage winding not only avoids the difficulties in moving the winding parts onto the toroid, but also does not result in any insulation problems, since these winding disks each have only a limited voltage range for the entire high-voltage coil have to record. Of course, the arrangement of the individual winding disks can also be adapted to the respective requirements, that is to say individual winding disks can be combined to form disk segments or symmetrical distances can also be set. An extraordinary further advantage can be seen in the fact that such transformers can now be constructed with individual modules, since the adaptation of the high-voltage coil to the current voltage can be carried out simply by plugging in more or less such winding disks. This modular design enables the rational production of large numbers of similar components and thus their and of course the economical production of transformers. In addition, the winding ends of these disk windings can also be guided to the outside, so that they can also be connected outside the transformer. Another remarkable advantage of such transformers is their light weight and small volume. In fact, such a toroidal transformer almost only contains the parts that such a transformer requires, that is, the primary and secondary coils and the transformer sheet wound in an ideal manner. Comprehensive yokes or sheet metal webs as with the usual transformers are completely eliminated, and with it their volume and weight. Of course, the weight savings due to the omission of a surrounding jacket is also remarkable, since the transformer cast with cast resin no longer needs such a jacket.

After process step 4, the hardened toroidal core is coated with an elastically flexible insulating material. This insulation material not only represents an electrical insulation layer to the toroid, but also enables a certain amount of heat to move both the toroid and the low-voltage coil pushed onto the toroid. This insulation layer is therefore an important feature of the invention, since it has been shown that with such transformers of greater output, the removal of the heat generated in these compactly constructed transformers can cause difficulties and therefore leads to thermal movements of the individual components. Since the casting resin into which the toroidal core transformer is cast can be considered rigid, such thermal movements, due to the different coefficients of thermal expansion of the different materials, ultimately lead to microcracks within the casting resin, which can lead to a change in the electrical field or to electrical breakdown . In the case of the toroidal core transformer constructed in accordance with the invention, on the other hand, these thermal movements resulting in the interior of the toroidal core transformer are absorbed by the elastically flexible insulating layer, practically without any action on the surrounding cast resin jacket. In fact, practice has also shown that transformers constructed in this way are free from such dangerous microcracks.

In this context, it should also be pointed out that the complete encapsulation of the transformer according to the invention has the advantage of extraordinary noise insulation. This becomes one causes that all parts of the transformer - iron core, low-voltage and high-voltage coil - are firmly embedded in the casting resin, on the other hand in that the casting resin forms a sound-absorbing layer around the transformer. However, this complete pouring is only possible through the insulating material layer inserted according to the invention.

A silicone is proposed as the preferred insulating material, which can be constructed to be both elastic and flexible with good electrical and thermal properties.

The winding disks of the high-voltage winding are usually wound in such a way that disks with a constant width result. However, in order to be able to fully utilize the volume of such toroidal transformers, it may also be expedient to wrap these disks in a wedge shape, that is to say that the sides facing the center of the toroidal core are made narrower than on the opposite side. Such a winding can be produced with the modern automatic winding machines without difficulty.

If high-voltage DC voltage is required, the transformer according to the invention can also be equipped with diodes for rectification. This can be done according to the invention in such a way that diodes assigned to each winding disk are arranged on or in the outwardly projecting casting ribs. The diodes are expediently accommodated in a vertical air shaft provided on the ribs. This has the advantage that the diodes against mechanical damage is protected, that it is accessible and therefore easily replaceable and that you are also sufficiently cooled by the air flow resulting in this air shaft. In addition to these advantages, there are also advantageous electrical voltage ratios, since each diode or diode arrangement is only acted upon by the partial voltage of a single winding disk.

Of course, the single-phase transformers constructed in this way can be connected in the usual way to three-phase transformers standing side by side. A particularly expedient embodiment results from the fact that the three individual transformers are placed on top of one another to form an “energy column” and anchored in this position. This not only brings spatial advantages, but also good heat dissipation through the rib-shaped parts of the transformers arranged one above the other. The anchoring is carried out in such a way that the individual transformer blocks can also be displaced in the vertical direction in order to compensate for the thermal movements.

Fig. 1

eine perspektivische Darstellung, teilweise geschnitten,

Fig. 2

die Draufsicht
und

Fig. 3

die Seitenansicht eines gewickelten Ringbandkernes,

Fig. 4

eine erste
und

Fig. 5

eine zweite mögliche Spulenanordnung,

Fig. 6

eine Draufsicht, teilweise geschnitten,

Fig. 7

eine vorgewickelte Niederspannungsspule in Ansicht
und

Fig. 8

im Querschnitt
und

Fig. 9

eine teilweise auf einen Halb-Ringkern aufgeschobene Niederspannnungsspule.

Fig. 10

eine "Energiesäule"

The object of the invention is shown schematically in the drawing, namely:

Fig. 1

a perspective view, partially cut,

Fig. 2

the top view
and

Fig. 3

the side view of a wound toroidal core,

Fig. 4

a first
and

Fig. 5

a second possible coil arrangement,

Fig. 6

a top view, partially cut,

Fig. 7

a pre-wound low voltage coil in view
and

Fig. 8

in cross section
and

Fig. 9

a low-voltage coil partially pushed onto a half toroid.

Fig. 10

an "energy pillar"

The toroidal transformer shown has a circularly wound toroid (1), which is divided into two halves by two cuts (2). Low-voltage coils (3), which were previously manufactured as air coils, are pushed onto these two ring halves, as shown in FIG. 9. Between the low-voltage coil (3) and the toroidal core (1) there is an elastic, flexible insulation layer (4). After this work, the two halves of the ring core are each cast separately, although the cut surfaces (2) of the ring cores are still free. Also shown (Fig. 1) are support elements (8), which are then placed on the low-voltage coil (3) when the toroidal halves finished to the low-voltage coil are not cast. These support elements, made of the same casting resin that is used to completely cast the transformer, determine the position of the high-voltage coils (5, 15) to be pushed on. The high-voltage coils (5 and 15) are then pushed over the ring core halves, as can be seen from FIGS. 4 and 5. After this work, the two toroid halves are on their cut surfaces pressed together and, for example by surface welding, fixed in this position and then cast with casting resin (6). During casting, the protruding winding disks of the high-voltage windings (5) give rise to ribs (7) which provide good ventilation for the toroidal transformer thus constructed.

Fig. 10 finally shows an "energy column" formed from three superimposed single toroidal transformers, which are held in this position by a central pressure rod (9) and a resilient clamping ring (8).

Claims (7)

Process for producing a mains power transformer encapsulated with casting resin, with a cutting core, preferably wound from a cold-rolled ferro alloy, which has a magnetic preferred direction, spirally wound in the magnetic preferred direction and strengthened by the addition of resin
through the following partially known process steps: 1. Coating the toroidal core (1) with an electrically insulating, but heat-conductive and heat-resistant, elastic and flexible insulation layer (4); 2. Cut the ring core (1) into two ring halves; 3rd a) pushing a low-voltage rectangular winding (3) made of enameled round, rectangular or profile wire on each ring half; b) if necessary, pushing one or more rectangular windings (3) onto the previously applied winding; 4th a) casting the wound toroidal halves or applying support resin made of cast resin (10); 5. pushing over each assembled high-voltage winding disks (5, 15); 6. Join the two toroid halves; 7. Connect or lead out the winding ends; 8. Casting the complete transformer with rib-like casting around the winding disks (5). Toroidal transformer according to claim 1,
characterized,
that the insulation is a silicone. Toroidal transformer according to claim 1,
characterized,
that the silicone is adjusted with regard to its coefficient of expansion to the coefficient of thermal expansion of the ferromaterial or the winding material; Toroidal transformer according to claim 1,
characterized,
that the winding disc width ≦ 40 degrees of arc of the inner ring core diameter. Toroidal transformer according to claim 1 or 4,
characterized,
that the side surfaces of the winding disks (5) run at an acute angle. Toroidal transformer according to claim 1,
characterized,
that ventilation channels for receiving diodes are arranged on the outwardly projecting potting ribs (7) of each winding disk (5, 15). Toroidal transformer according to claim 1,
characterized,
that three individual transformers are arranged resiliently one above the other.

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