Basic question, 3 phase terminology...

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dellboy

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Hi, feel free to laugh if this make me sound simple but here goes..

Firstly I am in the UK but cannot find any forums with any answers so I am here...

I have just commisioned a Hirzt F8 Multibore CNC machine for a friend.

There was an existing isolator outlet and cable run in of 4 core 2.5mm fire rated cable to a 16amp 3 phase breaker within the Distribution panel.
According the the colour code L1 was Brown L2 was Black and L3 was Grey.
I tested this back to the panel to make sure there were no issues with the existing installation and then connected according to the above.With no Neutral but an Earth as the machine does not require the neutral.
The machine fired up and after a bit of fiddling with CNC controls I set it to drill out a 35mm hinge hole in a door. Smoke ensued which indicated the Drill bit was running in reverse. I then Swapped L1 for L2 and tried again with success. I noticed however that on the machines block for wiring, at the top from left to right it says L1, L2, L3 and respectivley below each one it says R, S and T. Now I have not worked much with 3 Phase, but did cover it in the 16th Wiring Regs, (UK Standard for electricians) and have checked the book but can not find a definition for these.
This is my question what do R, S and T stand for in 3 phase terminoligy?

Thankyou for your time

Richie
 
As I recall, this is as close as I can get I think the r, s or t does not stand for any thing.
It is the manufactors way of denoting the coils winding.
The motor may go slower, faster or reverse.
Or may stop faster, depending on which phase is on r,s or t


If this we're a roller coaster it could be reverse, slow or thrilling:grin:
 
buckofdurham said:
The motor may go slower, faster or reverse.
Or may stop faster, depending on which phase is on r,s or t
Click to expand...

Never heard of such a thing... and if the above is true, I would really love to know more about 3-phase power in the UK. With US 3-phase, the A,B,C (or r,s,t) is totally arbitrary and the rotation is arbitrary. There is nothing about phase 1 that will distinguish it from phase 2 or from phase 3 (neglecting a high-leg delta system where one phase will have a higher voltage to ground). The power company may give you a counter-clockwise rotation while the premises next door may have a clock-wise rotation. And your "A" phase may be your neighbor's "C" phase. That is what I have seen.

Any of the POCO reps disagree? On a new service/bulding, do your linemen worry about rotation or any particular termination on the xfmr being "A" phase?
 
I really think it's just three letters mathematicians picked for no special reason. I doubt they stand for anything. Sorta like X and Y are used for the legs of a graph.
 
dicklaxt said:
It appears to be an "Alpha " noted sequence,if it holds any other meaning I don't have a clue .I got lucky in a search.


http://www.solcon.nl/gjkool/brushless5/W-schms-3p-E.JPG

dick
Click to expand...
Recently hooked up Italian-made transformers, gear, and motors, and a couple German motors. They seem to use U,V,W as phase notations. Perhaps it is more than coincidence that these are three back from X,Y,Z, and R,S,T is three back from these.
 
Agreed I'ver seen the u,v,w & x,y,z used on the old Star/Delta wiring diagrams with all 6 leads going from motor back to the 3 switching contactors but never saw the r,s,t reference

dick
 
national electrical code

national electrical code

Why the national electrical code for dwelling units don't apply the
continuous and non continuous load to calculate the over load protection
device and cable selection calculation, correction factors for temperature

The national electrical code discuses about the motor-compressor,
motor-compressor largest load, protective device, and no discussion about
air handling units, chillers

the national electrical code discuses the method of calculating the demand
load one panel board the question if I have panel (A) and (B), (C), (D),
each of them contain lighting , motors and sockets loads and appliances and
air conditions how I cane calculate the demand load for the main panel
MDB-1 that feed all this panel boards and the main feeder, main circuit
breaker and calculate the demand load of panel board MDB that feed the
(MDB-1), (MDB-2), (MDB-3), (MDB-4) ,main feeder, main circuit breaker where
(MDB-2), (MDB-3), (MDB-4) same as MDB-1 but different in loads not typical
and, also calculation transformer load.

The national electrical code discuses the demand loads of central space
heating only for optional method for dwelling units what about the general
method for dwelling units and the non-dwelling units.
 
R,S,T is a common labeling for 3 phase, LIne side In Europe, no different than L1, L2 and L3, A,B,C whatever. Germans use it all the time. On motors as others mentioned, U,V,W and X,Y, Z used fro terminal. No different than Your trypical 3 phase T1, T2, T3..... motor leads. Bottom line is that if you think rotation was wrong, by switching any of the R,S,T, same as switching L1, L2, L3 it did the trick. By the wire size OP mentioned sounds like a small CNC machine. By looking at the drill bits on the machine, proper rotation can be determined too. ( Rh, LH bit)
 
There is a very good IEC reason for this. If I knew what it was, I would let you know.:rolleyes:

Not being presumptous, just uneducated on why this is used. Have seen it in drives for industrial machinery from japan (Fuji, Yaskawa, Mitsubishi, Toshiba, Hitachi, etc.) and korea. It seems to be some type of regular goesin/goesout way of specifying things on drawings and terminal strips.

L1(R) (line in #1)
L2(S)
L3(T)

T1(U) (line out #1 to motor)
T2(V)
T3(W)

The only, only time I've seen the cardinal sin of disconnecting the metallic surfaces of a machine from the power cord, in other words defeating the 'earth ground,' was on a german printing machine. One of the mains fuses was IN LINE with what I usually call the "green earth ground," because our old fashioned U.S. earth grounding wiring scheme uses green colored wire. Needless to say, that machine did not receive a third party inspection sticker the way it was. Hope you never come across one of these.
.
 
Firstly , Thanks to all of you for the wealth of ideas.

I tend to agree with the general consensus that R,S and T stand for nothing but one thing still puzzles me....

With all the instructions that the machine came with (mostly in Italian) there is nothing to cover the basic connections of this machine. As far as I am aware this was bought as a complete product so all of the internal wiring / switch feeds and compressor lines are made buy the manufacturer and the machine shound be setup and ready to go. Just awaiting an installer to connect the 3 Phase supply, Compressed Air supply (for the clamps) and the Dust Extraction.

Now for me logic would dictate that from the 3 Phase Distribution Panel to the Machines hookup L1 would leave the panel and hit the machine on its terminal marked L1, and the same with L2, L3 and earth. In this case in order to make the machine work, we had to switch L1 for L2. I have no answer for this other than sloppy manufacture as I am sure it would make more sense to complete tha manchines internal wiring this way.

Apart from all this insignificant babble the machine appears to work well other than some accuracy issues which I am arguing with the supplier about because I believe that it is their responsibility to Setup and calibrate the machine before use as this is such an accurate bit of kit to do this is quite specialist work. But for ?18.500 brand new for CNC workshop equipment, my friend cant really complain...

Thanks again for all your advice and I look forward to my first visit to the US in september... (or as you would say "the fall")

Cheers

Richie
 
Again, the power company linemen, to my knowledge, take no particular pains to provide either a clockwise or counterclockwise rotation to a building unless it is specifically asked for, such as upon a service rebuild.

There is nothing that makes a given utility xfmr phase conductor the "A" phase or the "L1" phase. It is completely arbitrary. Plus, any given manufacturer of motors could wind their motors one way or another, which could vary the direction the motor runs with any particular phase arrangement as compared to other manufacturers.

so again, L1, L2, and L3 from the poco are completely arbitrary. What physical voltage or current characteristics are there that distinguished "A" phase from "C" phase?

Can the poco guys confirm this? Do your linemen have to keep track of which conductors are "A" phase all the way from the poco generator through the substations through the last xfmr so that "A" is always "A"?

I highly doubt it, plus, with delta-wye and such, the "A" being "A" becomes completely muddled anyway. So there is nothing that defines what the utility "A" phase is except what the linemen arbitrarily make it.

(of course there is a difference for the high leg if one is present.)
 
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