Railway Transformer Ntt 400 U

On-board power supply transformer


The REO onboard power supply transformer NTT 400 U is designed for onboard power supplies that are fed by the onboard power converter (BNU). The transformer NTT 400 U describes the complete, ready-to-use unit with transformer and housing. The transformer is used to adjust the voltage and for galvanic separation of the pulse-width modulated intermediate circuit voltage and the consumers of the onboard network. An appropriate sine filter must be connected between the transformer and the inverter. The secondary-side load of the isolating transformer can be switching devices, rotating machines, ohmic loads and semiconductor power converters. The transformers are designed for the use of vehicles in the AC or DC network (in inverter operation) in the container.

This guarantees that REO transformers are optimally aligned with your application. Longest service life, cost/benefit optimization and safety are the focus of our development.

Power: 10-30 kVA
Nominal voltage:


  • Nominal voltage: (normal operation): 3 × 440 Veff 60 Hz
  • Nominal voltage: (external supply): 3 × 400 Veff 50 Hz
  • Nominal voltage: (reduced operation): 3 × 345 Veff 47 Hz


  • Voltage: 3 × 230 Veff
  • Operating temperature: -25 ° C … + 55 ° C (optional + 75 ° C)
  • Humidity: max 95%
  • Pollution degree: PD4
  • Insulation class: F / H
  • Test voltage: EN 50124 / EN 60310
  • Vibration resistance: Category 1 Class A / B according to EN61373
  • Voltages: 24/42/110/230/400/690 volts (optional)
  • Switching group: Optional

Customized complete solutions

On-board power transformers can be customized. Are you interested in this product? Please contact us!

In addition to the standardized components for use in the converter, REO offers customer-specific products – as a single component or as a complete solution in a container. The benchmark in rail technology is the availability and safety of passengers. Here REO offers special solutions that are developed step by step in close cooperation with the customer.


  • Vibration and shock tested according to DIN 61373 Cat 1 Class B
  • High efficiency
  • low no-load losses
  • reduced field spread
  • low noise development
  • Weight optimized
  • high mechanical strength
  • Cooling ON
  • Pollution degree PD4
  • different performance classes


  • Nominal power: 10000 – 30000 VA
  • Input voltage: 3 × 440 V



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