ECN Forum Forums Technical Discussion Electrical Theory and Applications Zigzag transformer

I forgot the theory behind the

word Zigzag transformer. Could you explain

it to me. Am I right to say zigzag

transformer or Zigzag (Z) phase.

In the electric utility business Delta-ZigZag transformers are used because the secondary will tie with the secondary of a Wye-Wye transformer. My company uses both because the 12 kv secondary of a 115-12 kv Wye-Wye and a 115-12 Delta-ZigZag will tie with a 46-12 Delta-Wye.

A common use for a zig-zag autotransformer is to establish a grounded neutral in a 3ø3w system. A low-voltage example would be to derive a grounded neutral {for 277V loads} where the building is served by a 480V 3-wire ungrounded-delta transformer—literally providing a 480Y/277V 4-wire circuit from the ungrounded 3-wire service.

Likewise, “north of the border” a zig-zag autotransformer can be used to derive a neutral conductor for 347V lighting from a 600V 3-wire ungrounded-delta transformer—literally providing a 600Y/347V 4-wire circuit from the ungrounded 3-wire service. Three 240:240V 1ø transformers of the correct kVA could be used for either 3ø3w voltage.

EC&M magazine has had a couple of articles about serving 277V equipment from ungrounded 480V. See http://ecmweb.com/ar/electric_unconventional_transformer_connections/index.htm {Online version is without illustrations.}

I have posted a few Schematics of Zig-Zag setups in the Technical Reference section, but not any description of function or reasons for use. Check them out if you like.

If anyone would like to write up a text document which describes their functions and/or useage, please do so!!!

Send it to me in ASCII format (.txt), or RTF if you do not use MS Word. If you do use Word, the normal .doc format is fine.

Send to me via my e-mail address: adst at pacbell dot net.
Name the subject "ECN Zig-Zag Text" (without the "Quotes" of course).

Thx!

Scott