Do update that site when the meanings for these have been determined.
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"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Exactly how much more research would you like me to do for you?
Part of the educational process that seems to be lost on many students of all subjects is performing research to find answers to questions such as this.
You, somehow, managed to find this site. Now, use those same skills to determine for yourself any further meanings for the acronyms.
To paraphrase part of FAQ #14: Do your own homework!
The question is directed at everyone, not one person. Finding out from other people is part of research. If you 've run out of ideas, someone else might just have a longer list. So dont take it personal.
This refers to: Three-phase AC voltages as vta, vtb and vtc.
Please post the scan of original document, wherein you saw these abbreviations, if you are not satisfied with this answer. You will surely get an answer if you do so.