Discuss Three phases main supply in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
It doesn't ALWAYS have to be like that.
They could all be brown, but marked up as L1, L2, L3
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.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.
Yes you can do that at the machine.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.
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.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'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.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
Yes you can do that at the machine.
But what’s the point in ensuring phase rotation is consistent throughout an installation?
When I was in the RAF we had a hangar with 6 separate bays where we moved 3 phase machines with 125A plugs around depending on aircraft requirements. Bay 2 (I can even picture it right now) was wired the wrong way round meaning that every time a machine went in or out of there one of us had to swap the phases round. Our contractors were like you and couldn’t see the problem. Hours of work over years due to incompetence on the part of the original inspector that signed it off.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?
That’s probably a scenario where checking the phase rotation would be a good idea.When I was in the RAF we had a hangar with 6 separate bays where we moved 3 phase machines with 125A plugs around depending on aircraft requirements. Bay 2 (I can even picture it right now) was wired the wrong way round meaning that every time a machine went in or out of there one of us had to swap the phases round. Our contractors were like you and couldn’t see the problem. Hours of work over years due to incompetence on the part of the original inspector that signed it off.
Black and grey sleeved with brown to denote line conductors
If phase conductors are being used as single phase line conductors, then they should all be sleeved brown.Only if they are all on the same phase, if they are on different phases they should not be sleeved.
If phase conductors are being used as single phase line conductors, then they should all be sleeved brown.
You misunderstood me.Yes, that's what I said, the black and grey should be sleeved brown if they are on the same phase as the brown, if they are on different phases they shoukd not be sleeved brown.
It's Phase Sequence Lads not Rotation, from Pete999 the Pedant.That’s probably a scenario where checking the phase rotation would be a good idea.
How long did it take before you asked a Rock Ape to sort out the socket wiring?
You misunderstood me.
If the three phases are being used to supply single phase equipment, for instance 3 lighting circuits each on a different phase, then the conductors should be sleeved brown (or otherwise identified as being line conductors).
Wouldn't that depend on the neutral loading, harmonics etc?Why would you need 7 core?
5 core would do, share the neutral between the 3 phases.
Some machines don't like being run backwards. Best to get it right first time.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.
Then it would be one 3-phase circuit, but you were talking about three single-phase circuits:Why would you need 7 core?
5 core would do, share the neutral between the 3 phases.
Each of which will have a line and a neutral.for instance 3 lighting circuits each on a different phase,
Now how would you do that?Some machines don't like being run backwards. Best to get it right first time.
By machine I assume you mean 4 phase motors? if you have had any electrical work in your place of work, and you fear the phase sequence is not the same as it was, then I would suggest you uncouple the mechanical elements run the motor without any load to check you have the correct phase sequence for this particular motor, once you have checked and swapped phases at the motor, reconnect the mechanicals and off you go, as for taking the control from L1 surely it matters not which phase the control supply comes from.Now how would you do that?
How would you ensure that the new machine required the same phase rotation as that in your installation?
As far as I’m concerned, the only time ensuring phase rotation is the same throughout an installation would be beneficial, is if you intend moving a machine to various locations around an installation.
Also, most 3phase machines use L1 to supply control circuitry, so swapping phases around in an installation would help balance out loads.
Instead of all the control circuits being on L1, they would be spread accross all the phases.
The majority do seem to like L1, L2, L3 or R, S, T.How would you ensure that the new machine required the same phase rotation as that in your installation?
Good call Lucien, I was overthinking things, of course if you have the equipment, you could, as you say check and confirm phase sequence with a meter, what was I thinking of?????? DohhhhhThe majority do seem to like L1, L2, L3 or R, S, T.
In a factory environment where a board is only supplying 3-phase loads, each of which has three anonymous brown cables in an isolator or busbar tapoff, it's not particularly interesting to know which phase is which. You can test the sequence at the machine terminals before starting it up. But if you have a mixed load, where single-phase circuits might even dominate the total load at times and certainly overshadow the single-phase control loading of 3-phase machines, it's helpful to be able to balance them.
In the entertainment industry we use a lot of 3-phase supplies for mainly single-phase loads but with some 3-phase loads mixed in. I might plug a hoist control box into any one of a dozen 3-phase outlets in a venue. If I swap out some of the hoists, I don't want them to be overrunning their limits because they are wired the other way. At the same time, if I know there's a total of 160A to play with spread amongst three 125A circuits, I need to know that loading L1 to 100A in one DB and L2 to 100A in another DB is not going to catch me out mid-show because they are actually on the same supply phase.
I agree that it's not always essential to know which phase is which, but it's not terribly difficult to organise.
When I was in the RAF we had a hangar with 6 separate bays where we moved 3 phase machines with 125A plugs around depending on aircraft requirements. Bay 2 (I can even picture it right now) was wired the wrong way round meaning that every time a machine went in or out of there one of us had to swap the phases round. Our contractors were like you and couldn’t see the problem. Hours of work over years due to incompetence on the part of the original inspector that signed it off.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?
in my current role I work on wind turbine lifts which come with phase rotation relays. This prevents the lift operating in the event of incorrect phase connections.The majority do seem to like L1, L2, L3 or R, S, T.
In a factory environment where a board is only supplying 3-phase loads, each of which has three anonymous brown cables in an isolator or busbar tapoff, it's not particularly interesting to know which phase is which. You can test the sequence at the machine terminals before starting it up. But if you have a mixed load, where single-phase circuits might even dominate the total load at times and certainly overshadow the single-phase control loading of 3-phase machines, it's helpful to be able to balance them.
In the entertainment industry we use a lot of 3-phase supplies for mainly single-phase loads but with some 3-phase loads mixed in. I might plug a hoist control box into any one of a dozen 3-phase outlets in a venue. If I swap out some of the hoists, I don't want them to be overrunning their limits because they are wired the other way. At the same time, if I know there's a total of 160A to play with spread amongst three 125A circuits, I need to know that loading L1 to 100A in one DB and L2 to 100A in another DB is not going to catch me out mid-show because they are actually on the same supply phase.
I agree that it's not always essential to know which phase is which, but it's not terribly difficult to organise.
Now how would you do that?
How would you ensure that the new machine required the same phase rotation as that in your installation?
As far as I’m concerned, the only time ensuring phase rotation is the same throughout an installation would be beneficial, is if you intend moving a machine to various locations around an installation.
Also, most 3phase machines use L1 to supply control circuitry, so swapping phases around in an installation would help balance out loads.
Instead of all the control circuits being on L1, they would be spread accross all the phases.
Now how would you do that?
How would you ensure that the new machine required the same phase rotation as that in your installation?
As far as I’m concerned, the only time ensuring phase rotation is the same throughout an installation would be beneficial, is if you intend moving a machine to various locations around an installation.
Also, most 3phase machines use L1 to supply control circuitry, so swapping phases around in an installation would help balance out loads.
Instead of all the control circuits being on L1, they would be spread accross all the phases.
Reply to Three phases main supply in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net
We get it, advertisements are annoying!
Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.