Nuvotem Talema offer a custom-design service where our engineers design the most suitable power transformer for your application based on the electrical and mechanical specifications.

Toroidal Power Transformers offer significant advantages over conventional laminated transformers,

and Nuvotem Talema's technical design staff have vast experience in designing the best transformer for the application.

Generally the equipment designer is faced with the problem of 'squeezing' the power transformer into a confined space, and we, at Nuvotem Talema, have built up over 25 years of experience in designing toroidal transformers which fit into these confined spaces, and yet electrically and thermally out-perform the competition
With Nuvotem Talema's ability to provide instant EN61558 approval on custom designed transformers, the equipment designer does not need to adjust their design to suit a "standard" transformer, just to get an approved part.

To ensure that our engineers design the "right transformer for the job", we suggest that when requesting a quotation and/or sample transformer(s), that you provide us with as much technical information as you have available.

We would suggest the following information be provided:

• * Application
• * Primary voltage(s) (and tolerances if non-standard)
• * Secondary voltage(s) and current(s) or power rating(s)
• * Regulation requirements
• * Temperature Rise
• * Duty Cyle (if any)
• * Isolation voltage(s) and creepage / clearance distances required between windings

• * European standards (EN60065, EN60742/EN61558, EN60950 .. etc)
• * Physical restrictions (maximum available dimensions)
• * Special mounting requirements ?
• * Special connection wire configuration ? (Crimps, Connectors, Lead forming .. etc)

Nastro G.O.S.S. (acciaio a nastro con silicio a grani orientati)
G.O.S.S. Band (Grain Oriented Silicon Steel Band)

is a method of reducing the radiated magnetic field from a transformer, and is used on transformers for domestic and professional Audio and Audio Visual equipment.

Even though a toroidal transformer exhibits much lower levels of "Stray Field" or radiated magnetic field when compared to conventional transformers these levels may be reduced even further by attaching a screen to the outer circumference of the transformer.

Il Campo elettromagnetico
Stray field

Achieving low levels of stray field is an important consideration for the equipment designer as the phenomenon can create unwanted noise through interference with sensitive electronics.
A Toroidal transformer will generally offer a reduction of 8:1 in magnetic interference levels compared with traditional frame style laminate types.
Over the years, Nuvotem Talema design team has developed a range of successful techniques which can almost eliminate stray field. These specialists will be pleased to work with you on your specific requirements.

APPLICAZIONI
APPLICATIONS

When designing a transformer or inductor, Nuvotem Talema deign engineers always ask what the application is. Why is this ?

The application of a magnetic component can have significant implications in determining the most suitable design. Common applications would be :

• Security Systems
• Medical Equipment
• Professional Audio Visual
• Domestic Audio Visual
• Distribution / Standards
• Lighting LVL
• Lighting Dimming
• Medical
• Telecommunication
• Automotive
• Control Equipment
• Motors & Drives
• Battery Chargers

Each of the above fields of application have their own specific requirments for transformers and inductors.

For example, a power transformer for use in Domestic Audio Visual equipment would usually need to be designed using a low flux-density in the core to reduce the radiated magnetic field, have varnish impregnated core and windings to reduce the, physical "noise", and be wound using very uniform winding machines.
Depending on the equipment design, it may also require a magnetic screen (known as a GOSS Band) to reduce the radiated magnetic field. Generally the transformer must be UL recognised, and also conform the the requirements of EN60065 (IEC65) as a minimum.

Compare this to a toroidal power transformer for use in Low Voltage Lighting (12V Halogen lighting, know as LVL):
The important points for a lighting transformer would be the generated heat, the accuracy of the output voltage which affects the life of the lamp(s), the effectiveness of the overload protection device(s), and generally the physical space into which the transformer must be mounted is very restricted. On top of all this, the transformer must meet all the requirements of "short-cicuit proof" according to EN61558 (replacing EN60742).

Consider a power transformer for use in Medical equipment. There are requirements for the maximum permissible leakage current which can flow from the mains supply to the earth point, so the transformer generally requires a higher level of insulation between the primary winding and the earthed copper screen to ensure that the combination of all the possible sources of leakage current (mains cable, input socket, mains filter, transformer) remains within limits of EN60601 (UL2601).
The transformer will also generally require a thermal fuse or thermal switch of some type, which will switch off the power supply if a fault condition occurs in the equipment.

As may be seen from the above comparisons, the "field of application" of the transformer does indeed dictate certain design criteria, which have an important effect on designing the most suitable component.

Montaggio
Mounting Styles

Toroidal Transformers may be provided with a number of alternative mounting styles:

• * Standard Mounting Kit - 2 Insulating discs and dished metal disc
• * Centre Potted with threaded insert
• * Centre Potted with through hole for mounting bolt
• * DIN Rail monting
• * Horizontal & Vertical mounting brackets

Regolazione
Regulations

All Transformer windings have an internal resistance due to the length of the copper wire making up that winding.

From "Ohms Law" we know that when a current is passed through a resistance, there will be a potential difference or "Voltage Drop" across that resistance.

This is calculated as V = I.R. , where V=Voltage Drop , I=Current , R=Resistance.

Applying this logic to the secondary winding of a transformer, we can see that when no current is flowing in the winding, there will be no voltage drop across the winding. In other words, if we measure the No-Load output voltage of a secondary winding, we will be measuring the actual induced voltage (induced EMF).
However, once we connect a load across this winding, current will flow, and there will be a voltage drop across the winding. Hence, the voltage measured "On-Load" will be smaller than the voltage measure at "No-Load".
This voltage difference is known as "Regulation" and is normally expressed as a percentage of the full-load voltage.

Example:
Secondary winding designed to provide 10 Volts when delivering its rated current.
If we assume a no-load voltage of 11 Volts, we can then calculate :

Regulation = (11 - 10) / 10 = 1 / 10 = 0.1 = 10%

*NB* Some transformer manufacturers will divide by the higher figure (No-Load voltage) instead of dividing by the smaller figure. This gives a false lower regulation value.

Typical regulation figures for transformers from 15VA to 5000VA are shown below.

Variazione della temperatura
Temperature Rise

Toroidal Transformers generate heat due to the losses within the energy conversion processes. A typical graph of temperature rise versus power consumption would be as shown below. (Pout=Actual Power Output, Pnom=Nominal Power Rating)

Core Losses

Copper Losses

Approvazioni
Approval