Circuits and switching groups

The transformer factory Breimer-Roth GmbH identifies its three-phase transformers in line with the more common and user-friendly approach as follows:

The 1st capital letter describes the primary input winding and the 2nd small letter the secondary output winding.

If no other order information with more precise positional assignment of high and low voltage is formulated, the above-mentioned type of marking is selected! Three-phase transformers are preferably manufactured in Dyn5, if no other information is available.

Load capacity of the neutral conductor (star point)
In the star-star connection (Yy), the neutral point may only be loaded with the full rated current if the neutral conductor of the supplying network is connected to the primary-side transformer neutral point. If this is not the case, the star point can only be loaded with approx. 10% of the phase current.

The same rule applies to three-phase autotransformers which are designed in star-energy saving circuit (YNa0). If a fully loadable star point is desired, but this is not available on the mains side, the double zigzag connection (ZZan0) must be selected.