This is a usual question from electric system integrators, since apparently, distribution transformers should be a little bit more competitive
Usually, converter transformers are more robust than distribution ones, but it is true that in the same sense, they are less price-competitive. Here we stated some of the following points of interest in comparison to each one for shore connection applications:
- Converter transformers handle higher stress due to harmonic components in the load current
- With shore converters, the harmonics should be similar to a distributed grid, since there already is a sinusoidal filter integrated in the converter
- Converter transformers allow a higher thermal overload of the core and the pressed parts, due to converter disturbances, like pulse unbalances or an increased direct current component in the load current
- Yes, but this is not needed neither, since, although we normally ask for a 0.5% DC current to be in the safe area, the DC components and unbalances are negligible, and usually the standard distribution transformer margins should be enough
- There is also higher electrical load due to steep voltage peaks
- This is also true, since in the phase to phase voltage there is only sinusoidal voltage, but there are steep voltage peaks in the phase to ground voltage, due to common mode that is not filtered by the sinus filter which is differential
Our advise is to use transformers with improved phase to ground insulation, but without the need of over-sizing them due to harmonics.