Phase Rotation

[VIresistance]

Hi

I was wondering if someone help me with this please. I have my 2394/95 recently.

I was testing a industrial DB today and phase rotation at main switch was anti clock wise which is wrong.

The board is sub main from main board and plant room.

Why is wrong and is there any other reason it could course it to be wrong sequence part of wrong connection?

I am testing a few new circuits on that board and I will sign a certificate for it.

What do I need to do about it?

Thank you

 

[Andy™]

someone wired it wrong. it could be wrong sequence between meter & DB or DNO head wrong and its never been checked. swapping rotation is a simple job, however you will most likely end up with other problems and possibly do some serious damage if you do

 

[ProDave]

New install yet to be commissioned? or existing install with lots of working machines connected?

 

[VIresistance]

Does it definitely from wrong connection or could be from something else?

 

[Andy™]

Does it definitely from wrong connection or could be from something else?

yes, all the power stations in the country stopped their generators one night and re-started them the opposite way

or someone could have wired it wrong

is the main DB correct or not?

 

[VIresistance]

I am going to investigate tomorrow, I have noticed other 2 DB was the same.

Can I still sign the certificate with that problem?

 

[ProDave]

What certificate?  I presume you mean en EICR?  Of course you can sign it, you have to sign it regardless of what you find.

 

[VIresistance]

It is a new installation certificate. Few sub contractors have installed new lighting circuits in that DB and I was testing them, but of course at page number 3 ( schedule of item inspected) the box verification of phase sequence need to be ticked, what do I need to put in that box if the electrical company hasn't done anything about it?

 

[Andy™]

get them to put it right.

also phase sequence and phase rotation are different things

 

[apprentice87]

Well pointed out Andy!!!

john...

 

[Tony S]

The company I served my time with had their own power station, no national grid back then. It ran BYR, when our system connected to the grid the phases had to be crossed at the intake.

Phase rotation is arbitrary.

That is until you have to install interconnects then it gets interesting. Two incoming feeds to a switchboard, one is BYR the other RYB. The back of the board looks bizarre but the outgoing ways were all our standard BYR.

If the entire site is BYR what difference does it make? You’re a brave man if you tell the company to get the intake reversed.

 

[Andy™]

then you can also get problem if part of the building is wired wrong...

fitted a new  TPNE socket in a factory adjacent to a DB. they had a machine at the other side of factory they want to move about. gets called back a day later to say the machine wasnt working (came up with rotation fault). my socket was wired correctly... DB at other end of building wasnt...

 

[apprentice87]

Phase rotation is most certainly NOT arbitrary, and i am not even an electrician and i can tell you that. Electric motors are wound so that a conventional phase rotation will cause them to rotate, in, so far as i can remember, a clockwise direction when looking at the end of the output shaft.

john..

 

[Tony S]

Read what I said.

It’s your fault if you connected sockets without checking. Are you going to reverse the intake to the DB in question and then reverse every outgoing 3Ph way?

Mark the board with “phases reversed” and swap the phases in the sockets.

We had 12MVA running BYR, 6MVA running RYB. Muggins put a few interconnects between plants but I knew which direction they ran. As I said the back of the switchboard looked weird but everything was clearly marked up.

Many of the site electricians didn’t even know about the reversal, they would work on one plant from “cradle until grave”. I was like horse muck, I got everywhere.

The first plant construction project I was involved in the contractors site manager had a bet with me, “95% of the drives will run the right way.” He lost the bet 95% ran the wrong way and I was all the b******s under the sun. Even more so when I made them change rotation in each drive terminal box. I won £1.

Phase rotation was clearly marked on every drawing issued.

Looking at the DE of a motor shaft RYB → A1B1C1 on a new motor should give clockwise rotation. Rewinds it’s anyone’s guess.

 

[Tony S]

Phase rotation is most certainly NOT arbitrary, and i am not even an electrician and i can tell you that. Electric motors are wound so that a conventional phase rotation will cause them to rotate, in, so far as i can remember, a clockwise direction when looking at the end of the output shaft.

john..

Tell several power stations that.

Rotation is arbitrary, convention isn’t.

10/10 for the motor rotation hence the “scoob”.

Rewinds are a nightmare. When connecting any new or rewound motor test run it with the load disconnected first. The one time you don’t will be the time you cause £K’s of damage.

 

[apprentice87]

Not that i do much of this sort of thing, but i ALWAYS test the supply, and then my meter can identify the motor leads when you turn the motor by hand. Match up the leads and right first time!!

There was a college near me that was being demolished. I had a snoop about, and their supply was wired up wrong. Every DB had a sticker saying "non conventional phase rotation" or something like that. Why would anyone do something daft like wire an entire building wrongly??

john...

 

[Tony S]

Depends who rewinds it and if its done properly.......

True but even the most respected rewind houses make a balls up. Do you think a multinational will use “Dave’s Rewinds”?

I’ve had them come back with a phase winding reversed, rotation I never trust.

The classic, they hadn’t connected the windings to the lead outs! It came with the test certificate stating everything was perfectly OK including rotation. It resulted in a sizable compensation claim for lost production.

Not that i do much of this sort of thing, but i ALWAYS test the supply, and then my meter can identify the motor leads when you turn the motor by hand. Match up the leads and right first time!!

There was a college near me that was being demolished. I had a snoop about, and their supply was wired up wrong. Every DB had a sticker saying "non conventional phase rotation" or something like that. Why would anyone do something daft like wire an entire building wrongly??

john...

Read #11 first then look up “network design guide”.

Out of interest, how do you know the intake was wrong?

 

[apprentice87]

I will try to explain...

The supply to the entire site terminated i presume, in a brick building not far from the boundary. A submain then ran a few hundred yards and popped up in the room where all the electrical intake stuff was located.

Here is a photo of the incomer..

http://i1178.photobucket.com/albums/x373/resistance87/1.jpg

Here, in this photo you can see that the incoming submain terminals were about a foot away!!!

http://i1178.photobucket.com/albums/x373/resistance87/2.jpg

Why would you go and get a little sign, and then repeat this at every DB in the entire place, [there must have been hundreds] instead of just swapping the cables at the incomer???

As i say, i am no expert, but it seems daft to me, why would you not test at the intake position near the road, and then make sure you had the submain connected correctly when they first started the install??

john...

 

[Tony S]

Because some wet behind the ears fool came and said the plant is entirely wrong. The supply and every 3Ph supply “must” be reversed because my meter says so. I’d like to hear the conversation when they “insist” everything is wrong.

If the incoming supply and all subsequent feeds are BYR can you explain where the problem is?

BTW, a big chunk of NW England is BYR. Some of it is 30° out of phase, work that one out.

 

[Tony S]

Don't know, never used them, perhaps thats one you used to used but can't remember  :innocent

Yep, always check before connecting it up and ruining £1K's worth of equipment, however thats just common sense and good workmanship

In the 30+ years i have had small to big stuff rewound by a multi national worldwide rewind company - i can honestly say i have never ever had anything run the wrong way

Perhaps I'm just lucky, although i do have a very good relationship with them locally to me and drink with quite a few of them and also do all their inverters for them

Perhaps your just unlucky  :innocent

Who knows

Ill open another red and look at the red lights and blackpool on another post and ponder those thoughts.......

I can remember the companies well enough but I’m not naming them, but you would know them if I did.

Can we stop this “bragging rights” campaign?

BTW,

I live in a red light district, who needs Blackpool?