Products - Conventional transformers

Types and features | Series index | Technical information

Conventional transformers HR - Technical information

  1. Ambient temperature Ta:

    denotes the air temperature measured near the transformer and under the equipment usage conditions. The temperature indicated on the transformer must not be exceeded %1 due to keep the functional safety parameters.

  2. Thermal class:

    it indicates the highest temperature that any material in the transformer can reach when working. It is shown with the letter printed after the Ambient Temperature according the regulation IEC60216 (E - 120º C) (B - 130º C) (F - 155º C) (H - 180º C).

  3. Primary voltage:

    it is the voltage to be applied to the transformer, due to achieve the secondary power indicated for the secondary working conditions.

  4. Nominal secondary voltage:

    it is the voltage supplied by the transformer to the secondary at the indicated current, and the primary is at its nominal value.

  5. Nominal power:

    the power indicated in the catalogue belong to the secondary supplied by the transformer, when the primary gets the nominal tension and under the indicated temperature conditions, for example: (3,2 VA ta 40 B). For dual secondary this power corresponds to the sum of the two windings.

    If the secondary of the transformer is connected to a bridge rectifier to convert to D.C. voltage, you must choose a transformer with a current 1.4 times higher from the continuous current need in the charge.

  6. No-load secondary voltage:

    It is the voltage supplied by the secondary, without any connected charge Is=0.

  7. No-load/load voltage relation:

    relation between secondary voltage to no-load and load conditions. This information is useful for designing power supplies, its regulation range and safety parameters.


  • External protection (E):

    the suggested fuse type for the transformer protection is indicated on the body of the transformer. Even though if it is in primary or secondary, the location and type of protection to be used, is under the designer's responsibility.

Fuse types:

Depending on the protection fuse location in the primary or secondary winding, the correct fuse type must be chosen.

  • Type T:

    temporised in the primary circuit.

  • Type F:

    fast in the secondary circuit.

Heating information

It is the difference between the hottest part inside the transformer (winding) in stable working conditions and the ambient temperature.. It can be calculated with the measurement of the winding wire resist. You can find different methods and formulas to be calculated, you may also consult our Technical department (ATD).

Adapted transformers form the standard serie

Any other transformer which requires special power features between our maximum and minimum value range can be manufactured according the costumers technical specifications. All the approval certificates from the standard serie as well as the product safety and reliability will be kept.

Special Transformers

Any other type of transformer with special characteristics, can be designed by our R+D department in collaboration with the costumer due to get the best results in their applications and obtain a reliable and safety product. Use the custom transformer form in order to get the best solution for your needs.