Technical characteristics

  • Mono-phase and three-phase transformers
  • Autotransformers
  • Different dimensions (plate/tall)
  • Power: 3-10.000 VA mono-phase, 10-30.000 VA three-phase
  • Primary voltage: 220V; 380V; on request
  • Secondary voltage: up to 5000V
  • Variable number of windings
  • Flash tested: 4kV peak
  • Frequency: up to 400Hz
  • Insulating materials: class E (120C), B (130C), F (150C), H (180C)
  • Protection class: IP 00
  • The magnetic stray field - the toroidal transformers have the stray magnetic field almost 10 times smaller comparing to laminated transformers.  This advantage owes to the construction of the core, which is wound from a continuous ribbon of steel and to the windings that uniformly encase the core in cooper like a shield, so the magnetic field is held inside the transformer. This way the need for special screening protection can be eliminated, toroidal transformers being suited for sensitive electronic applications like: amplifiers, medical equipments, etc.
  • Protection against short circuit and overload:
    1. Transformers that do not resist at short circuit will be protected using a fuse in the primary circuit.  They will have on the label the symbol
    2. Transformers that resist at short circuit and that are protected by incorporated devices will have marked on the label the melting temperature for the thermal fuse and the symbol.
      It is also recommended to protect it by using a fuse in the primary circuit.
  • Inrush current. The execelent magnetic properties of the toroidal transformers can cause a high magetizing current on turn on. Normally the duration of the inrush current is less than 10 ms and produces no problems in smaller power transformers.

For higher power transformers we reccomed the following types of protection :

  1. 15 VA – 300 VA – no protection neded
  2. 300 VA – 1 kVA – slow blow fuse
  3. 1 kVA – 2 kVA – small value resistor in series with primary circuit
  4. 2 kVA – 10 kVA – NTC thermistors or start-up circuit like in figure 1



All our products are made according to customers request.

fig 1

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Technical characteristics Technical characteristics
Toroidal transformers ...
Metode de determinare Methods of determining
secondary current ratings in D.C. circuits ...
Advantages Advantages
Toroidal transformers...

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