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3 phase plugs

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TJC

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Any particular reason? It is possible to use one phase of a three phase outlet if you wire a 3ph plug appropriately.

That's an observation, not a recommendation.
 

Cabinetman

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Hi Maxpower, well that certainly would give you your namesake!
You can’t accidentally get them in the wrong one if that’s what you were thinking. Ian
 

Sideways

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If you have a device that needs a neutral, you can't plug it into a socket that doesn't provide one.
 

Max Power

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Thanks, had a check and there's four wires, so I just wire the four into the correct terminals of the five pin plug ?
 

Cabinetman

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Sorry I hadn’t understood your question originally. I recommend you don’t go any further and get somebody in who really knows what they’re doing! Three-phase isn’t to be messed about with. Ian
 

bowmaster

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Does a 3 or 4 pin 3 phase plug fit into a 5 pin socket ?
No because the pins are positioned in such a way so as to ensure that only the correct plug type can be inserted into the corresponding socket. They are also colour coded to reflect the service voltage: Yellow 110v, Blue 230v and red 400v. The number of pins corresponds to the requirement of the machine you are trying to power. Typically 3-pin will be single phase (L,N,E), 4-pin will be 3ph + Earth (typically motors) and 5-pin will be 3ph + Neutral + Earth
 

Chrispy

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My workshop wired professionally is fitted with 5 pin sockets, most of the machines that are not hard wired have no need of a neutral so only use four of the five pins.
I opted for 5 pin sockets to try and future proof things.
 

TJC

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Yes, you can wire 4 pins in a 5 pin plug, but you need to be absolutely sure that you have the correct pinout and phase rotation. You may have to contend with mismatched colour code standards, or no colour coding at all on the machine side. If you're not 100% sure don't.
 

Jelly

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Thanks, had a check and there's four wires, so I just wire the four into the correct terminals of the five pin plug ?
In a word, yes.

However, I would eco TJC's point that if it's at all unclear on which wires are which at the machine side, (or you're unclear on which lines go to which pins because it's a second hand machine and the phases have been deliberately rotated by a previous owner), then you'll need to clarify that by looking at a wiring diagram, and possibly verifying with the continuity tester function of a multimeter; if that sounds like too much complexity it's definitely worth getting a trusted sparkie to do it.

Also, if you have armoured flex (which is like SWA cable, but less so), it's worth unbraiding and gathering the armouring wire together when you strip the cable, heat-shrinking it to keep it together and insulated then connecting to the earth terminals.
 

Max Power

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Thanks everyone, I've got a rotary converter which I use with other machines, that has a 5 pin female but the latest purchase (a union 10"double wheel pedestal grinder for £56 :oops: ) has four wires
 

NetBlindPaul

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Just a comment, SWA is not a suitable cable for termination into plugs and use as an extension lead.
 

Jelly

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Just a comment, SWA is not a suitable cable for termination into plugs and use as an extension lead.
But you can purchase "armoured flex" as well, which is produced with stranded cable, finer armour strands and a more flexible sheath.

However if you got some, and failed to earth the armouring strands, the benefit of the armouring would be reduced and induced currents could do bizzare things elsewhere.
 

NetBlindPaul

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But you can purchase "armoured flex" as well, which is produced with stranded cable, finer armour strands and a more flexible sheath.

However if you got some, and failed to earth the armouring strands, the benefit of the armouring would be reduced and induced currents could do bizzare things elsewhere.
I believe that you are referring to SY cable, with the clear outer sheath, and it is NOT armoured flex.
There is also, no recognised acceptable method for termination of SY (or CY) cable into a BS 1363 plug.

The braid in SY (& CY), is for EMC screening/control, and is not designed by the cable manufacturer to take full fault current in relation to the core size as a correctly specified SWA would.

Also, SY cable is in some dispute at the moment, as it has no recognised British Standard for manufacturer, and the standards quoted by many of the cable makers are a little irrelevant to the overall performance, for example one cable OEM quotes a German DIN standard which refers only to the flame propagation of the insulation, nothing else, another often. quote DIN standard number is in fact for a series of standards many of which are not directly related to the cable performance in use.
There are SY cable manufacturers who are going through the process of getting their cable recognised, but their issue is that there is no international standard (IEC), for SY, so there is nothing to validate the cable against.

Being an “approved” electrical contractor, TUV Certified Machinery Safety Expert, and also running my own engineering company doing primarily design and consultancy for other electrical contractors, machine builders and end users, accompanied by a smattering of I&T, build works, modifications and maintenance on machinery and electrical installations, I have to be pretty au fait with the various wiring materials and thier correct application.
 

Jelly

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I believe that you are referring to SY cable, with the clear outer sheath, and it is NOT armoured flex.
This I was unaware of, and I have been sold SY as "armoured flex" by reasonably reputable electrical distributors in the past when I've gone in for 3ph+E flex, so there's clearly a misunderstanding which is somewhat common and actively being spread there.


There is also, no recognised acceptable method for termination of SY (or CY) cable into a BS 1363 plug.
Nevertheless, I've seen it terminated into CEEForm 3ph+E and 3ph+N+E plugs (so IEC 60309, not BS1363) fairly frequently in existing installations.


The braid in SY (& CY), is for EMC screening/control, and is not designed by the cable manufacturer to take full fault current in relation to the core size as a correctly specified SWA would.
I can certainly see the issue there if someone was to use 3 core SY and treat the control braid as earthing in that case.

However I have been advised in the past that it is good practice to connect all unused conductors in cables to earth at both ends, by people more skilled in the art than I.

If you feel that's bad advice, I will consider my advice updated.


Also, SY cable is in some dispute at the moment, as it has no recognised British Standard for manufacturer, and the standards quoted by many of the cable makers are a little irrelevant to the overall performance, for example one cable OEM quotes a German DIN standard which refers only to the flame propagation of the insulation, nothing else, another often. quote DIN standard number is in fact for a series of standards many of which are not directly related to the cable performance in use.
There are SY cable manufacturers who are going through the process of getting their cable recognised, but their issue is that there is no international standard (IEC), for SY, so there is nothing to validate the cable against.
That sounds familiar enough, there was an analogous situation with GRP process piping and pressure vessels, where the BS standard was withdraw as depreciated because it didn't guarantee compliance with all design requirements in the most recent Pressure Equipment Directives...

But it took about 5 years for a new, (mostly) analogous EN standard to be adopted, during which time it was neccessary to fully justify design methodology and calculation methods in the technical file to demonstrate compliance, which is a huge PITA.


Being an “approved” electrical contractor, TUV Certified Machinery Safety Expert, and also running my own engineering company doing primarily design and consultancy for other electrical contractors, machine builders and end users, accompanied by a smattering of I&T, build works, modifications and maintenance on machinery and electrical installations, I have to be pretty au fait with the various wiring materials and thier correct application.
As a Chemical/Process Engineer I normally stop at the control architecture and expected electrical loads, then leave the finer details like that to someone such as yourself who is "Suitably Qualified and Experienced".

Maybe throw in some fault-finding on why a 4-20mA instrument isn't working properly, with an instrument tech, if they can't find an electrical reason for the fault condition.

It's always interesting to learn more about related fields though!
 
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NetBlindPaul

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I can certainly see the issue there if someone was to use 3 core SY and treat the control braid as earthing in that case.

However I have been advised in the past that it is good practice to connect all unused conductors in cables to earth at both ends, by people more skilled in the art than I.

If you feel that's bad advice, I will consider my advice updated.
Not withstanding, to ensure that there is no mistaken interpretations.
I would always expect the braid to be connected to the protective conductor system at the supply end.

The issue with the braid and earth currents comes from the misunderstanding of many with regard to the function of the braid.

With SWA, you can use 2 core for 1ph, with the cores for L&N and the armour ac CPC, the same with3 core for 3ph (no N), and the same with 4 core (3ph +N), with the armour as CPC.
With a few exceptions which are noted in the relevant documents and guidance to electrical designers.

SY/CY cannot be used in this manner, for 1ph you need 3 core for 3ph (no N) you need 4 core. for TPNE you need 5 core.

Termination in CEEFORM plugs is not quite as bad as termination n BS 1363’s, but strictly speaking the cable should be terminated in a gland which a CEEFORM trailing plug/socket arrangement does not allow.

The connecting of unused conductors to the protective system at both ends is now recognised as a potential means of generating EMC and unwanted circulating currents depending on the structure of the cable. A better option is to connect them to the protective system at the supply end, and connect them together at the load end. Though using them as a parallel cpc in a conventional cable is normally fine.
The braid on an CY/CY is not considered an unused conductor.

There is a misconception regarding SY, it has been adopted by many as a replacement for metaflex cable. It is difficult to find this material these days even on the internet to show an example, but it was a sheathed flexible cable, like normal 3 (or whatever) core flex on a kettle, but it had a close fitting metal screen/sheath over it, which very much resembled metal flexible conduit, (think bare Copex type) the difference was the two could not be separated, the cable was ”part” of the flexible conduit.
I can only find what appears to be a similar but solid cored version used in the USA, known as BX type. This is very similar to what I know as metaflex.

As metaflex (this might not be the real name, it’s just what we called it at work) disappeared from the market, SY was adopted to replace it by some. Even though it was not suitable, as it did not provide the same level of mechanical protection.

I hope this helps to explain a little more some of my comments.
 
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