Zig zag transformers
Zig zag transformers
(OP)
Could someone explain quickly how these work to create a neutral? Are they only tied to a ground? Are these considered to be grounding transformers? Under balance loading is the principle to carry zero current?
--peetey
--peetey






RE: Zig zag transformers
They are three-phase transformers connected to each phase and to ground.
You can get the same effect by using a delta-wye transformer, leaving the delta unconnected (or connected, actually).
Zig-zag transformers are rarely used these days in the US.
RE: Zig zag transformers
By connected, do you mean connected to and supplying a load, or connected in delta rather than leaving the delta open or "Broken delta"?
respectfully
RE: Zig zag transformers
The delta-wye transformer provides a good ground source (on the wye side) regardless of what load, if any, is connected to the delta side.
When we need to add a grounding transformer these days, we normally recommend a delta-wye transformer instead of a zig-zag due to availability and cost.
RE: Zig zag transformers
* Normal operation: The positive and negative sequence voltages are unaffected since the excitation impedance is very large.
* SLG fault: The system will see only small leakage impedance. Therefore, zero sequence impedance current will flow trough the ground as much as the rated neutral current and preclude current to flow in the phase conductors.
b) Are they only tied to a ground? No. The primary terminals are connected to the 3 wires ungrounded system in one end. The primary and secondary winding are interconnected as an autotransformer in a 1:1 ratio. The secondary windings are connected in a common neutral point and this is connected to the ground as shown in the enclose link. ht
c) Are these considered to be grounding transformers? The zigzag described above is for grounding applications. If another winding connected in delta is wound on the same core as the zigzag connected winding, the transformer is capable for power transmission with stable grounding and not phase shift.