Cast Resin Transformers (CRT)



Cast Resin Transformers are specially adequate and reliable for installations which require extreme Safety Standards, Reliability and Environment protection. Low and High Voltage windings built in Aluminium and embedded in resin class F or above, are the best solution when we look for non-pollutant, fireproof qualities and the compliance with the E2-C2-F1 standards. These transformers are designed for indoor use, however if installed in the appropiate IP cabinet they withstand outdoor conditions. Designs up to 36 kV are already available.

Technical Features

Major advantages:

  • Compact design. They do not require significant area/volume to be installed.
  • Easy installation. They can be located straight next to the load, without need of special fitting-out or installations, like pits, firewalls and/or special foundations.
  • Very low fire risk. Building materials with autoextinguishing capacity, make unnecessary the use of special precautions against fire.
  • Minimum Maintenance. Free cooling liquid design. Only requires periodic cleaning and check of connection tightening.
  • High capacity in front of temporary overloads. The design with low current density windings and high thermic endurance resins permits a high capacity to withstand short-term overloads. Tables below show the behavoir according to room temperature and load status (as % of nominal power) prior to the overload.
tcz_p_er_g03 tcz_p_er_g04
  • Important Power Reserve. The addition of forced ventilation allows the increase of the nominal power up to 25%.
  • Environmentally friendly. Once the transformer is completely manufactured its components are non-contaminant and in case of generalized room fire or a fire produced by the transformer, toxic gas emissions are insignificant.

Indoor installation (1)

In order to use full capacity of the CRT transformer, the indoor installation in closed premises must allow the intake of fresh air through S (m2) lower surface ventilation and a hot air outlet through S1(m2) upper surface ventilation. Both ventilation ducts are located on opposite walls with a height difference H (m). Lower duct (S) must be at the lowest level of the transformer. (P) represents the total losses of the transformer (in kW), and the following condition must be complied:


When the required ventilation is not naturally feasible, the installation of a forced ventilation system will be necessary. The blowing device should have the capacity to remove at least 4.5 m3/minute of air, per each kW of total transformer losses (P).

Safe Electric Distances (1)

The minimum safety distances from the High Voltage coils are:


(1) For more details please referring to Installation and Maintenance Manuals



  • Off-load bridge tap-changer ± 2 x 2,5% on the HVwindings.
  • Primary terminals for wire connection.
  • Secondary terminals for bar connection.
  • Lifting lugs.
  • Dragging lugs.
  • Grounding terminals.
  • Bi-directional wheeled boggie.
  • Name plate.


  • Off-load bridge tap-changer, special regulations.
  • Pt 100 type thermo-resistors on LV windings and Fe Si core
  • Temperature monitoring unit with output signals for alarm and forced ventilation start and check.
  • Forced air cooling system for nominal power increases up to 25%.
  • Clamp box for auxiliary circuits.
  • Metal protection cabinets (IP 20, IP 21, IP 23 and IP 31). Other options on request.
  • Electrostatic shields
  • Bimetallic Plates for LV and HV sides
  • Temperature monitoring unit with special functions.
  • Polimeric(Ozn) surge arresters

Tables with specifications




Quality, Health, Safety & Environment

Installation and Maintenance Manuals