Trafo

Trafo (Transformador) – Comprehensive Guide

1. Main Types of Trafo

(1) By Cooling Method
  • Oil-Immersed Trafo

    • Uses insulating oil for cooling, suitable for high-voltage and high-capacity applications (p.ej., grid substations).

    • Common Models: ONÁN (natural cooling), ENCENDIDO APAGADO (forced air cooling), OFAF (forced oil and air cooling).

  • Dry-Type Trafo

    • Oil-free design, insulated by air or resin, ideal for fire-sensitive environments (p.ej., hospitales, centros de datos).

    • Common Models: SCB (epoxy resin-cast), SG (open-type).

(2) By Application
  • Distribution Trafo

    • Niveles de voltaje: 10kV/0.4kV, used for end-user power supply (p.ej., residential areas, fábricas).

  • Power Trafo

    • Voltage levels ≥110kV, used in transmission networks (p.ej., substation main transformers).

  • Special Trafo

    • Includes rectifier transformers (for electrolysis), mining transformers (explosion-proof design), etc..

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2. Especificaciones clave

ParámetroDescripción
Capacidad nominalp.ej., 100kVA, 5000kVA; must be calculated based on load.
Relación de voltajeInput/output voltage (p.ej., 10kV/0.4kV).
Voltaje de impedanciaTypically 4%~10%, affects short-circuit current.
Connection Groupp.ej., Dyn11 (common for distribution), Yyn0 (balanced low-voltage loads).
Método de enfriamientoONÁN, ENCENDIDO APAGADO, OFWF (oil-immersed); ENCENDIDO/APAGADO (tipo seco).
Efficiency ClassChinese standard (ES 20052): Clase 1 (highest efficiency), Clase 2, Clase 3.

3. Applications

  • Power Systems: Voltage step-up/down, grid interconnection.

  • Industrial: Power supply for motors, hornos (custom impedance may be required).

  • Renewable Energy: PV/wind grid integration (must withstand harmonics).

  • Rail Transit: Traction transformers (25kV/50Hz).

4. Selection Guide

  • Indoor Installation: Prefer dry-type (fireproof) or fully sealed oil-immersed.

  • Outdoor Installation: Oil-immersed (protection class ≥IP55).

  • High Load Fluctuations: Choose models with strong overload capacity (p.ej., ONAF cooling).

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5. Preguntas frecuentes

Q: How to choose between oil-immersed and dry-type transformers?
A: Oil-immersed offers lower cost and higher capacity but requires fire protection; dry-type is safer for confined spaces.

Q: How to calculate required capacity?
A: Sum all load power (kVA) and reserve 20%~30% margin.

Q: How to reduce transformer noise?
A: Select low-noise designs (p.ej., step-lap core) or install soundproof enclosures.

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