Three phases main supply

[dj2102]

Where i can find in the regulations that the always has to be
L1 - brown
L2 - black
L3 - grey

 

[rsgaz]

Table 51.

 

[westward10]

Section 514.

 

[dj2102]

ok thanks

 

[littlespark]

It doesn't ALWAYS have to be like that.
They could all be brown, but marked up as L1, L2, L3

If you're referring to how a 3 core cable connects to one of the old colours, then yes... its
L1 - Red - Brown
L2 - Yellow - Black
L3 - Blue - Grey

Black and grey sleeved with brown to denote line conductors

 

[dj2102]

It doesn't ALWAYS have to be like that.
They could all be brown, but marked up as L1, L2, L3

I know that the technically it doesn't matter. But if you have lots of motors in your company you have to keep it eye on it.

I wanna know clearly what regulations talking about it.

 

[Deleted member 26818]

There is a requirement to ensure correct phase rotation throughout an Installation in Chapter 6.
I think it’s a bit pointless, as when you connect 3 phase machinery, if it runs backwards, you just swap one of the phases over.

 

[littlespark]

There is a requirement to ensure correct phase rotation throughout an Installation in Chapter 6.
I think it’s a bit pointless, as when you connect 3 phase machinery, if it runs backwards, you just swap one of the phases over.

Reminds me of a huge job on RAF Leuchars where every mains cable was replaced. 185mm armoured cables.... turned it on and EVERY motor was running backwards.
Not my fault, BTW... I was just there pulling cables into trenches

 

[Pete999]

There is a requirement to ensure correct phase rotation throughout an Installation in Chapter 6.
I think it’s a bit pointless, as when you connect 3 phase machinery, if it runs backwards, you just swap one of the phases over.

Agree but you can do that at the machine can't you? thus not altering the phase sequence at the incoming supply to the machine switchgear.

 

[Deleted member 26818]

Agree but you can do that at the machine can't you? thus not altering the phase sequence at the incoming supply to the machine switchgear.

Yes you can do that at the machine.
But what’s the point in ensuring phase rotation is consistent throughout an installation?

You have an installation where phase rotation has been checked throughout.
You install a new machine, it runs backwards.
You swap the phases round in the machine, it runs forwards.

You have an installation where phase rotation has not been checked throughout.
You install a new machine, it runs backwards.
You swap the phase round in the machine, it runs forwards.

What’s the difference?

 

[Pete999]

Yes you can do that at the machine.
But what’s the point in ensuring phase rotation is consistent throughout an installation?

You have an installation where phase rotation has been checked throughout.
You install a new machine, it runs backwards.
You swap the phases round in the machine, it runs forwards.

You have an installation where phase rotation has not been checked throughout.
You install a new machine, it runs backwards.
You swap the phase round in the machine, it runs forwards.

What’s the difference?

I was trying to make the point that the phase sequence wouldn't change at the point of connection to the equipment from the supply, if you wanted to keep the sequence the same throughout, that's all.

 

[telectrix]

It doesn't ALWAYS have to be like that.
They could all be brown, but marked up as L1, L2, L3

If you're referring to how a 3 core cable connects to one of the old colours, then yes... its
L1 - Red - Brown
L2 - Yellow - Black
L3 - Blue - Grey

Black and grey sleeved with brown to denote line conductors

i'd never sleeve black and grey with brown on a 3 phase installation. we never sleeved the yellow and blue. only brown sleeve when used in single phase circuit/s.

 

[davesparks]

Yes you can do that at the machine.
But what’s the point in ensuring phase rotation is consistent throughout an installation?

The requirement is to ensure phase sequence rather than rotation. This means that you need to ensure the none of the phases get swapped around, so L1 at the intake is connected to L1 everywhere. If this is not ensured then you could have L1 in two different parts of the installation with 400V volts between them when there should be 0V.

 

[plugsandsparks]

Also makes balancing a head scratcher if the phases keep moving around from Db to Db. I try and keep L1, L2 and L3 consistent from MDB to Dbs. I have had one install where rotation was backwards from the service intake.... did grumble a bit on that one.
I also never sleeve brown on black and grey, very confusing when i came across one that had been done that way, ended up cutting the sleeves off for the same reason tel said.

 

[chris gray]

I’d over sleeve brown with black and grey but not the other way round