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#162363 - 04/18/07 05:43 AM What is the meaning of "R-S-T" in 3-phase system?
PaulC Offline
New Member

Registered: 04/17/07
Posts: 2
Loc: Ohio, USA
I'm trying to find the reason the 3 phases are named "R-S-T" in a unit from Taiwan. Is it just something someone came up with like "A-B-C" or could it be an acronym for something?
I've found that it's used in various places like Sweden and Korea. But Google doesn't come up with much else. Pointing me to the appropriate standard(s) would be super.
Thanks much.
Paul

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#162364 - 04/18/07 06:29 AM Re: What is the meaning of "R-S-T" in 3-phase system? [Re: PaulC]
JBD Offline
Member

Registered: 07/12/01
Posts: 595
Loc: WI, USA
It is not an acronym.

There are many different numbering schemes.
On motor contactors, manufacturers in the US usually labeled their incoming connections as L1, L2, L3. And then they will use T1, T2, T3 as the load terminals. In other parts of the world, terminals were labeled R, S, T and U, V, W.

A common current practice is the dual numbering scheme of L1/1, L2/3, L3/5 and T1/2, T2/4, and T3/6

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#162367 - 04/18/07 07:14 AM Re: What is the meaning of "R-S-T" in 3-phase system? [Re: JBD]
LarryC Offline
Member

Registered: 07/05/04
Posts: 719
Loc: Winchester, NH, US
So which is it?

R=L1, S=L2, T=L3, U=T1, V=T2, and W=T3?

Or

R=T1, S=T2, T=T3, U=L1, V=L2, and W=L3?


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#162372 - 04/18/07 09:22 AM Re: What is the meaning of "R-S-T" in 3-phase syst [Re: LarryC]
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Originally Posted By: LarryC
So which is it?


RST is the incoming supply, UVW and XYZ are the motor connections.

See here: TOS lathe - manual Y Delta start switch

I remember looking through a catalog when I was a kid and seeing RST on a European phase-rotation tester and wondering what, if anything, the letters meant.

Other letters can be found to identify phases. Here in the U.K., for example, we often used RYB for red/yellow/blue, the standard phase colors (well, until recently!).

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#162379 - 04/18/07 10:33 AM Re: What is the meaning of "R-S-T" in 3-phase syst [Re: pauluk]
PaulC Offline
New Member

Registered: 04/17/07
Posts: 2
Loc: Ohio, USA
Thanks Paul for the explanation. I did run across the U.K. "RYB" earlier in my search but didn't pick up on the red/yellow/blue linkage. I think the colors used sometimes here in the states are like red/blue/black. This of course confuses the Black/Red of DC power systems. Oh well.
My solutions will be to have our friends in Taiwan do some text editing. Thanks again for your input.

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#162422 - 04/19/07 01:09 AM Re: What is the meaning of "R-S-T" in 3-phase syst [Re: PaulC]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2236
Loc: Vienna, Austria
I was once told XYZ are generator terminals, UVW are motor terminals (the other set of terminals are usually U1, V1, W1) and RST are terminals of a receptacle and other stuff in/ on the walls.

The motor designations have stuck, receptacles, panels and everyting else now have the standardized L1, L2 and L3 all across Europe.

Phase colors way back were black, red and blue too! That is if there was no ground wire. In that case the phases would have been black, blue and grey. Unless there was a neutral... then the phases were black, blue and black.

Guess why that color scheme was abandoned in the 1960s... ;\)

Side note: in reality at least in Austria all those colors were hardly ever used. Conduit wiring mostly had all 3 phases the same color, for example 3 blue wires and a red one for the ground.

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#162426 - 04/19/07 02:21 AM Re: What is the meaning of "R-S-T" in 3-phase syst [Re: Texas_Ranger]
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Originally Posted By: Texas_Ranger
Phase colors way back were black, red and blue too! That is if there was no ground wire. In that case the phases would have been black, blue and grey. Unless there was a neutral... then the phases were black, blue and black.


Sounds like the guy who dreamed that up had spent a little too much time at an Austrian beer festival!

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#162433 - 04/19/07 03:36 AM Re: What is the meaning of "R-S-T" in 3-phase syst [Re: pauluk]
RODALCO Offline
Member

Registered: 12/08/05
Posts: 852
Loc: Titirangi, Akld, New Zealand
Thanks Pauluk for putting in that link.

We discussed that topic already not too long ago.

R,S,T is now superseaded with L1, L2, L3 or A, B, C or R, Y, B in the South pacific.
_________________________
The product of rotation, excitation and flux produces electricty.

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#162655 - 04/22/07 11:48 PM Re: What is the meaning of "R-S-T" in 3-phase syst [Re: RODALCO]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8472
Loc: SI,New Zealand
All the new stuff here in NZ is Red,White,Blue.
Although there is a LOT of older stuff that uses the older type colour scheme.
We have been told to use the Yellow heatshrink up first before getting into the White stuff.
Darn bean counters!! \:\(
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#162712 - 04/24/07 07:54 AM Re: What is the meaning of "R-S-T" in 3-phase syst [Re: Trumpy]
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
All the new stuff here in NZ is Red,White,Blue.


Weird that -- In Britain we changed the B phase from white to yellow in the mid 1960s, while in N.Z. you've just done the reverse!

How long before you guys go for the new brown/black/gray?

Ducks for cover.....

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