Finding the compromise between coupling and isolation
High insulation
in thin thicknesses
A transformer operating at high frequency has two opposing needs:
- a good coupling between the windings to reduce the dispersed inductance to the minimum possible – this involves the proximity of the various windings to each other;
- good insulation between the same windings to allow high insulation between low voltage circuit parts and high voltage circuit parts,
this implies the need to introduce insulating materials between the windings which increase the distance between them, with a negative effect on the dispersed inductance.
The insulating materials introduced between the windings must be particularly good, because they must be able to withstand variations in electrical potential of high amplitude, with a frequency of thousands of times per second, and with a duration of many years. Ambient temperature also influences the behavior of insulating materials, and this must be taken into account.
Sirio manages to obtain a good compromise between these two opposing needs, reducing the thickness of the insulation to a minimum: an appropriate choice of materials and the use of vacuum impregnation allow the objective to be achieved. The company is equipped with 5 small, medium and large impregnation plants.
The pre-drying and post-hardening processes of the impregnated transformers complete this technology. This know-how allows us to achieve insulation levels above 20kV/mm.
Repeatable construction from first to last piece
Constant characteristics
In high frequency each transformer must be mechanically the same as other transformers of the same model. In fact, small variations in the arrangement of the winding turns lead to different couplings between the same windings. Different couplings cause different electromagnetic behavior of the same transformers, with possible consequent malfunctions in the electronic circuits in which the transformers are used.
An operator, no matter how good, is unable to maintain the same mechanical precision throughout the working day if he uses manual winding machines, where the perfect consistency of the positioning of the coils depends exclusively on his skill. Sirio has solved the problem by enriching its machine park with a large quantity of automatic winding and welding lines.
These lines guarantee mechanical precision of less than a tenth of a millimetre.
Being controlled by computers, automatic machines eliminate the possibility of errors such as incorrect counting of the number of turns or possible incorrect insertion of layers of insulating material.
Furthermore, they guarantee perfect attachment of the wires to the output pins, and the quality of the soldering of the wires to the pins is also automatically checked.
Finally, it should be underlined that the high level of automation, in addition to positively influencing the quality of the winding, reduces production times and therefore also costs.
To meet the requirements of the industrial market
Reliability over time
Sirio transformers must be inserted into industrial equipment that must function correctly for many years. They must therefore have a longer life than the life expected for the equipment itself.
The reliability of Sirio transformers over time is obtained through the combination of various factors:
- the use of high quality materials;
- the control of production processes through tests that follow the progress of production step by step;
- final testing on 100% of production.
Sirio is equipped with a large fleet of instruments and automatic control lines.
There are two other important factors that positively and decisively influence reliability over time:
- the codified design, production and testing procedures – the Sirio company has been ISO9001 certified since 1994;
- the absence of partial discharges inside the insulation in the operating voltage range of the transformer.
Partial discharges damage the insulation over time, to the point of creating short circuits inside the transformers.
How to eliminate them and how to detect their presence?
The Sirio vacuum impregnation technology allows us to eliminate the presence of air vacuoles and therefore partial discharges within the insulation layers.
Furthermore, the company is equipped with instruments capable of detecting the presence of partial discharges of even a few pico coulombs, with test voltages of up to 30 kV.
