Zigzag transformer

The zigzag connection (English: Three -phase inter - star or Zig -Zag ) is used for the load distribution on the low voltage side of three-phase alternating current transformers for powering low -voltage networks. It can be a combination of star and delta connections be considered and will be marked in the switch group with the letter "z".

Function

In this type of circuit at the output as in the star circuit has two voltages ( eg 230 /400 V ) are present, as it also has a Sternpunktanzapfung, but they can withstand unbalanced load such as a delta connection.

In the delta and star connection, the individual windings are always only on one leg. Wherein the zigzag circuit but the coils are divided into two equal parts. Two of the winding parts are distributed on two legs. So an unbalanced load on the secondary side to the outer conductor of the primary side is better distributed. The generated by the single-phase unbalanced load flow of current to the secondary side is distributed over two legs, and thus on two outer conductors of the primary side.

This advantage comes with the following disadvantages:

• It takes about 15 % more copper
• More copper results in larger winding losses
• Because of the higher losses there are transformers with this type of connection only to 400 kVA.
• The manufacture of transformers with the zigzag circuit is more complex.

In principle, a double - zigzag circuit is possible. Because of the primary and secondary side zigzag connection of material and manufacturing cost is increased and the circuit interesting at best, for special cases. If one chooses a suitable switching group (not Zz0 or ZNzn0 ) of the transformer to the power transmission are involved in a single-phase load windings on all three legs. In this case the magnitudes of the currents to the feed lines form the ratio 2:1:1.

Use

Use is the zigzag circuit in three-phase transformers with greatly unbalanced load, eg in transformers for the supply of emigrants courtyards.

Footnotes

• Transformer