Last Update 5/03/2007
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TECA S.p.a.
TECA S.p.a.

Via 4 Piccoli Martiri, 3
25040 Cividate Camuno
(BS) Italy
P.Iva 00691310981

TEL. ++39 (0)364 342001
FAX ++39 (0)364 344676
Email: info@teca.net


 

 




The electromedical and electronic equipment used in medical and hospital environments, given its particular use, needs extremely stringent safety standards.
  Index





TECA's toroidal transformers produced for electromedical equipment fully respect the norms of quality and safety specific to that sector, according to the following standards:

• EN61-558-2-15 regarding specifications and particular characteristcs of insulation for transformers which supply medical sites. Essential electrical characteristics are: maximum supply voltage of 1000Vac, maximum exit voltage below 250Vac, frequency below 500Hz, power between 3kVA and 10kVA, monophase or multiphase.

• EN60601 regarding general safety norms for electromedical equipment. In particular supply transformers must be adequately protected against overload (protected through construction, protected but not through construction or protected against faults), the coils must be adequately insulated so as to limit dispersion current within the values established by the norms. Electrostatic screens may be placed between the insulation of the various coils to increase galvanic insulation.

• UL544 (norm which refers to the North American market) regarding medical and dental equipment. Particular attention is paid to the differences between pieces of equipment which come into contact with the patient in different ways (patient care equipment or non-patient equipment). Here too the maximum values of dispersion current, galvanic insulation, safety protection, self-extinguishing capacity and the circuits necessary to carry out these checks are all established precisely.
Since transformers for electromedical equipment have characteristics which differ greatly from transformers in general use, it may be useful to underline some important points which demonstrate the attention with which TECA produces and tests these objects which are indispensable in equipment for check-ups, diagnosis and care, all fundamental for our health.


Dispersion current
 

This type of non-functional current crosses or slightly touches the insulation and can be divided into:
• Dispersion current towards earth when it flows from the network connection towards the protection conductor or along the insulation (with a maximum value of 3.5mA for the norm EN61-558-2-15 and a value of 2/1/0.5 mA for the norm EN60601 appendix k, depending on the class of equipment;
• Dispersion current on the protective cover when it flows from the protective cover or part of it towards earth or towards a different part of the protective cover itself across an external conductor (which should not be the protection conductor, maximum value 0.1mA for the norm EN60601);
• Dispersion current in the patient when it flows from the part applied to the patient towards earth or from the patient towards earth through an insulated applied part (0.1mA norm EN60601).
It is easy to understand that the maximum values of the currents established by the norms are extremely low, given the dangers for the safety of the patients. This is why TECA is extremely careful both in the design phase and in the successive production phases to produce coils with particular characteristics and also to increase the thickness of insulation, all of which helps to limit the dispersion current.

Equipment
 

Any electrical or electronic device destined for use near to and/or attached to the patient in such a way that his safety can be affected may be defined as electromedical equipment. For example: diagnostic apparatus (like electrocardiographs, X-rays, ultrasound devices for nuclear medicine etc), equipment for therapy and surgery (defibrillators, muscle stimulators, dentists' drills etc), general equipment (dentists' chairs, operating tables etc).
Equipment used in the medical sphere can be categorised on the basis of how far it is from the patient:
• Patient equipment: equipment used in sanitary structures near the patient, for example paramedical applications, dialysis rooms, dentists' surgeries etc;
• Non-patient equipment: equipment used in sanitary structures but not used near the patient.
The fact that TECA knows the final use of the equipment allows the company to design and test the transformers together with the client according to the specific application; this will certainly be less expensive and less complex in the case of non-patient equipment, compared with the cost for patient equipment.

Screens
 

"Separation between two coils or protection of one part or of the whole transformer by means of a conducting material for functional reasons"
This is the official definition of screens supplied by the technical norms, where the aim is to increase safety conditions and the performance of the transformers, reducing the dispersion current and increasing the level of insulation between the coils with high voltage and the other coils.
Thanks to the production of electrostatic screens between primary and secondary coils connected to earth, produced with binding tape, with insulated copper film, wound over all the surface, the galvanic insulation value is significantly increased (insert detail of electrostatic screen).
A qualitative and functional aspect to be considered in the presence of electronic components is the need to limit the magnetic flow lost; this is because magnetic disturbances can interfere with electronic details of particularly sensitive medical equipment. The particular configuration of a continuous core without butt-gaps or discontinuity typical of the toroidal transformer already in itself guarantees a significantly reduced dispersion flow compared with a traditional transformer. But for some versions particular electrostatic screens are produced which prevent all dispersion of magnetic flow.




Protections
 

A further classification for electromedical transformers can be made according to the type of electrical protection against overloads and short circuits, in three groups:
• Resistent to short circuits due to the way it is constructed: design and construction methods guarantee that the temperatures do not exceed the limits specified in the norms during overload and/or short circuit and that when the fault has been removed, the transformer goes back to its regular function without damage or deterioration in the coils and insulation;
• Resistent to short circuits but not through construction: the transformer has a device that is an integral part of it which prevents the temperatures established by the norms being exceeded in cases of overload and/or short circuit, through the interruption of the supply to the circuit, with a return to regular function when reset or when the protective device has been replaced;
• Not resistent to short circuits: in this case the part relative to the protection of the transformer is the responsibility of the user, who should provide his equipment with protective devices which will guarantee conditions of protection and safeguard all the electrical in cases of overload and/or short circuit. All the protection values to use for correct protection, according to tests and trials indicated by the norms of reference, are shown on the transformer's label.
As for all the other technical and construction aspects, TECA recommends the client to use forms of protection suitable for the type and function of the equipment.

Tests
 

As we have seen, the aspect of safety is paramount for electromedical transformers, thus the tests that these transformers must pass are very strict. In particular:
• The test of the dialectric seal of the insulation establishes a resistance that is more than doubled, with a single voltage test which is for double or reinforced insulation
• The dispersion current between the input and output circuit when the input is supplied at nominal voltage and at nominal frequency must not exceed 3.5mA (norm EN61-558-2-15), measured with the circuit shown in the diagram:


• Insulation test for the coils with the application of a voltage spike five times the nominal voltage at a frequency of 300Hz.
TECA performs these and other tests on all the transformers produced, so as to always guarantee the total quality, reliability and safety of its products; the company, if requested, also provides the customer with a test report, information on tracing the batch and personalised technical files.

Productions
 

?As well as versatility in size for TECA transformers, allowing a wide number of different choices in diameter and height for every power and voltage, particular configurations can be produced with personalised input and output terminals, so as to satisfy every customer's requirements:

• STANDARD VERSION: the primary and secondary terminals leave the transformer at the same point;


• OUT OF PHASE VERSION: the terminals of the various secondary circuits are positioned differently from the primary, and out of phase among themselves;


• 90° VERSION:
the terminals of the secondary circuit are at 90° to the primary;


• OPPOSITE VERSION: the terminals are at 180° to each other;


• OPPOSED VERSION:
the terminals of the primary and secondary circuits leave from the same point of the transformer but in different directions, one up, one down;


• SIDE VERSION: the terminals of the primary and/or secondary circuit leave from the side of the transformer.


To complete the service it is possibile to produce cabling and personalised terminals and connectors so as to facilitate efficient installation, all with various types of terminals and contacts, from the most important and experienced companies in the field, produced on automatic machines in a specific depertment inside the company (see section on cabling in the general catalogue).

Specific applications
 

TECA does not only produce mono-phase toroidal transformers, but also three-phase and six-phase groups for large plants or industrial supply in the medical-hospital sector, always respecting the specific norms for the sector. As well as the attention to aspects of safety and perfomance in these transformers, one can also note the compact design, the presence of devices, cabling systems and installation systems of an industrial type, the particular attention to protections and to limiting input current using softstart, multi-voltage input with the possibility of obtaining a universal set of voltages which allows the transformer to be used anywhere in the world without further adaptors. For more details and further information, consult the section “Industrial supply” in the general catalogue.
In the electromedical sector it is essential that equipment working at network voltage has an insulation transformer with a transforming ratio of 1:1, which guarantees galvanic insulation from the network. In this situation, the need to supply several pieces of equipment requires the use of system transformers outside the equipment. TECA's technical staff can solve these problems by producing specific supply systems inserted into metallic boxes, completely insulated and potted, with supply leads with plug, command switches, protections and connecting plugs according to the customer's specific requirements (insert photo of metallic box).

 



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