Inductor devices – Polyphase
Patent
1983-08-09
1986-05-13
Kozma, Thomas J.
Inductor devices
Polyphase
336 92, 336150, 336198, 336213, H01F 3300, H01F 2730
Patent
active
045889716
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an electric transformer which is primarily but not exclusively applicable to the so-called "medium" power values, that is to say within the range of 5 to 1000 kVA approximately, and for single-phase or polyphase circuits.
The present invention is also concerned with a method for the construction of this transformer.
Known transformers comprise in a very general manner a magnetic circuit of sheet metal having certain zones surrounded by a high-voltage and/or low-voltage electric winding. The adjectives "high" and "low" are used here only in a relative sense to designate the circuits connected to the terminals of the apparatus between which the voltage under service conditions has respectively the highest and the lowest value.
There are different known methods of mounting an electric transformer; certain methods consist in mounting the electric circuits first, other methods consist in mounting the magnetic circuit first. In all cases, electrical insulation between the electric circuit and the magnetic circuit is achieved by means of insulating varnish with which the electric wires are coated and also by means of paper interposed at the time of assembly between the circuits of different types. In spite of this, it is also necessary to provide a gap between the electric and magnetic circuits; under service conditions, this gap is filled with electrically insulating oil contained in a tank which also houses the electric and magnetic circuits.
This conventional arrangement is attended by many disadvantages. During construction, the fitting of insulating paper is a delicate operation and difficult to perform automatically. Once the circuits have been completed, they have to be subjected to a long drying process under vacuum in order to extract the moisture from the large quantity of paper which is present and which is capable of performing its electrically insulating function only when it is dry.
Furthermore, the efficiency of a transformer is higher as the windows of the electric circuits are more completely occupied by the magnetic circuit. The gap which must necessarily be provided between magnetic circuit and electric circuits in the present state of the art plays an unfavorable part in this respect. It is also unfavorable from the point of view of weight and overall size of the apparatus. Furthermore, this gap entails the need to mount the electric and magnetic circuits independently of each other, which is made more difficult by the fact that the attachment means must afford resistance to the abrupt and violent forces which are liable to result from the appearance of a short-circuit in the power system to which the transformer is applied.
The aim of the invention is to overcome these disadvantages by proposing a transformer which is easy to construct and provides higher efficiency in spite of a smaller overall size.
In accordance with the invention, the electric transformer, comprising a magnetic circuit as well as, for each phase, a high-voltage electric circuit and a low-voltage electric circuit both wound on at least one section of the magnetic circuit, is characterized in that the electric circuits are arranged within at least one electrically insulating annular coil form which, under service conditions, is interposed between these electric circuits and the aforementioned section of the magnetic circuit.
Thus, the coil form ensures perfect insulation between the electric and magnetic circuits without entailing any need to provide either insulating paper or a gap between these circuits. The presence of the coil form considerably facilitates the winding of the electric circuits and also the construction of the magnetic circuit which can form with the coil form a practically rigid interengaged assembly whereas, in the present state of the technique, it had hitherto proved necessary to avoid any mutual contact between magnetic and electric circuits at the risk of damaging the insulation of the electric circuits. The coil form can be securely attached without any difficulty t
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patent: 2908880 (1959-10-01), Steinmayer et al.
patent: 3201734 (1965-08-01), Halacsy
patent: 3218592 (1965-11-01), Barrick
patent: 3617965 (1971-11-01), Trench et al.
patent: 4338657 (1982-07-01), Lisin et al.
Kozma Thomas J.
Societe Nouvelle Transfix
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