ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Old European phase designations

I found an explanation for the RST phase designations once commonly used in Europe. Older motors had XYZ (connected to the windings), UVW (connected to the incoming lines) and generator and outlets had RST.

Hi Ranger,
I've always wondered about them designations.
And also why RST was used, as opposed to say ABC.
The first time I ever picked up a European Electrical book, it took me a wee while to work out what they mean't.
Our motors use A1,B1,C1 and A2,B2,C2, I think that this is based on the British system, but I could be wrong, too!.

i will add here for north american phase destation are L1,L2 L3 or A ,B, C but for motors useally labled as T1, T2 ,T3 but we do see few older phase labels too like you say RST and WXY etc .. oh oh yeah motors also add on as T11,T12,T13 etc etc... and the transformer genally label as H1 ,H2,H3 ( hi volts ) X1,X2,X3 and the nuetural gernrally is X0 or H0 one of the two ..other wise i will try to find some more north amercian verison destation and french phase genrally are RST also or UVW one of two but i belive they do change it also but will check with my freind what he have to say with it


merci marc

The RST coding is something I wondered about ever since I first saw those designations on some European test equipment when I was a kid (thinking back on it, I reckon it must have been a phase rotation tester).

It's certainly strange to those of us who are used to seeing A,B,C, or L1,L2,L3. Still, I suppose the R,Y,B (red, yellow, blue -- phase colors) seen sometimes in British circles would seem strange to outsiders.

They could mean something in German perhaps?

No. it's just the alphabet backwards, from the motor winding terminals to the generator terminals.

I suppose the alphabeth forwards would have been too logical even to the Germans...