cable core colours for 3 phase motors

SY might not comply with the 18th edition (having got 15, 16 and 17 I've given up on keeping up to date), but it's been standard fitment for exposed flexible 415V cables to movable machine tools for decades. SWA is unsuitable for that use.

There's generally no need for it in internal cables, but it works.

PS:- electrons are colour blind...

Edited By Mark Rand on 19/09/2022 08:41:40

A couple of comments:

SY cable IS armoured. It is not "steel wire armoured" (SWA). SWA is a different class of cable.

SY cable is flexible (SWA is not)

While it is good practice to ground the braid in SY (and SC) cable, it is not technically necessary for electrical safety. This is because there are two layers of insulation between the conductors and the braid. These are functional (around the conductor) and basic (over the functional, under the braid. The clear outer layer adds another layer of protection against accidental contact with a live conductor.

The fact that SY cable comes with a Green/Yellow Protectice Earth (PE) conductor should make it clear that the brade is not intended for use as a protective ground.

Cable and wire does NOT have to be UKCA (or CE) marked. Made up assemblies like "cordsets" used for computers and the like do. In fact cable, as a component, should not be UKCA (or CE) marked as such a mark could be taken to mean a cordset made with it was compliant when it might not be.

Despite what the IEEE would like us to think, BS/EN 7671 is NOT a regulation. It is a standard. There is no legal requirement to comply with it (one exception, below). It is however the easy route to show compliance wiht the actual regulations (basically it has to be safe). The excepton is rented properties where somehow we have made it a legal requirement to comply with a commercial standard which is not good practice. That particular law is badly written becuase it specifies the 18th edition. so when the 19th comes out either the law will have to amended or work done to an old edition...

Robert G8RPI.

Actually SY cable should not utilise the braid as earth protection:

https://www.voltimum.co.uk/content/earthing-cable

I have known SY used in an application where it moved and the braid broke and pierced the insulation to the conductors. I think SY is intended to be used in static applications and not required to flex. In the car factory it was the standard cable for connecting static devices and many miles were used. In applications where regular movement was required it was not specified or used.

Mike

Edited By Mike Poole on 19/09/2022 10:13:05

Spec from Cleveland cables for SY CY and YY instrument/control cables at the following link.

For clarity SY is NOT cosidered an armoured cable, in fact some of the braided screening leaves much to be desired, it can be very widely spaced, unlike SWA where multiple steel wires cover the full circumference of the cable.

**LINK**

Emgee

EMGEE,

From your link:

CLEVELAND CABLE COMPANY DATASHEET | 1
APPLICATION
SY cables are used as an interconnecting
cable between fixed and mobile equipment in
conveyors, assembly lines, production lines and
machine tool manufacture where the galvanised
steel wire braid armour gives excellent
mechanical protection

It's flexible and armored. There are different degrees of amouring, it is NOT Steel Wire Armoured (SWA)

Pete R.

I think that is what everyone is saying, You can't use it as the Protective Conductor ("earth wire" i.e. to carry fault current from the load, but it should (not must) be connected to the protective conductor so it cannot become live in the case of cable damage. typically this is done by forming the braid into a pigtail(s). Some glands designed for SY cable have slots to allow the pigtials to be clamped under the nut.

That would be a very rare occurrance. We use SY at work to power fully mobile demolition plant in and over the last 25yrs I've seen it smashed, squashed, crushed, sheared in two and torn clean out of the plugs and sockets many, many times but I've never see the braid forced through into the conductor without it being completely flattened under a steel track or accidentally caught by a clumsy operator.

Robert

Definitely not classed as an armoured cable and I have fitted hundreds of the correct glands to secure the braiding, how many have you fitted. ?

Emgee

Better description here:

Edited By Emgee on 19/09/2022 12:28:54

wouldn't consider rubber to be oil resistant. In fact I'd be surprised if you can still get it. Google will give you the current colour codes

Latex Rubber has been replaced with Ethylene–Propylene Rubber and Neoprene Rubber in modern specifications (Type HO7RN-F for instance).

So current "rubber" cables demonstrate good resistance to oils fats and greases, and most aliphatic hydrocarbon solvents...

But are still quite susceptible to damage by slightly polar solvents (aromatics, ketones, chlorinated solvents), which do tend to be rather aggressive towards just about any kind of elastomeric polymer in fairness.

??? Why is Darakhshan Muquaddas post of 12:56 identical to Roy Entwhistles's at the start of this discussion ? Strange.

You are being obtuse.

Look at the datasheet https://www.clevelandcable.com/electrical-cable-stock-range/control-flexible-cable-with-or-wo-braid/SY-control-flexible-cable-pvc-up-to-95mm/

It clearly states: " Armouring: Galvanised Steel Wire Braid Armour "

That is also only one supplier website, I'm not going to bother linking all the ones that say armoured on the first page.
While it is not my day to day job I have installed plenty of cables including SY, CY. YY. SWA, MICC etc etc. This does of course include fitting glands.
I have also designed installations and equipment using CY, SY & YY cables. That included certification to international standards CE, UL ULc Ctick & CSA for starters.

Robert G8RPI.

I just looked at the cable colours of 4 different makes of 3 phase motors on the Inverter Drive Supermarket website and they were all different. Only the tag codes were common, which is not much help, unfortunately.

For me, it's never been important what colour the phases are in the cable, just so long as the other one can be identified.
Does anyone want to enlighten me?

It's much easier to wire a new plug or, or break into the wiring to replace a component (say an isolator switch that has failed) if all the power supply wiring in a machine is using one of the standard colour codes; doesn't really matter if its:

• the old Red-Yellow-Blue,
• the new Brown-Black-Grey, or even
• the American Black-Red-Blue and Brown-Orange-Yellow...

But in terms of making life easy down the line, it matters that they're clearly distinguishable, and the phases remain consistent with their colour code (e.g. there isn't a hidden point in the circuit where an L2 coloured wire swaps to being a L3 colour, even if the wires are changing from old to new colour codes).

​

At a push, wiring them all in a single colour, but tagging each wire with a number referencing back to a wiring diagram, as per panel-wiring practice can be OK...

But I for one would much prefer it if people reserved this for final drive wiring which goes through a reverse switch only, and maintained as much of the power transmission wiring in machines as is practical following one of the standard colour schemes.

​

I have developed strong opinions on the matter after repeatedly having to unpick the design choices of long since retired electricians and instrument techs who chose to repeatedly deviate from both standard practice and the original designs without ever thinking to update the wiring diagrams (even crudely annotating them with red pen or a pencil would have been be better than nothing).

If phase rotation is important it's always best to confirm the 3 phase conductors ID is correct using a Phase Sequence testing instrument before connecting/testing any 3 phase equipment that relies on correct phasing.

Emgee

One example where I think colour coding doesn't matter much is the internal wiring connecting a motor inside a machine. The motor only has 3 connections and the only thing that can go wrong is the motor running in reverse, which is easily fixed. A 3-phase electric oven wouldn't care at all how the phases were wired. Or am I talking rubbish again?

Of course colour coding is useful in many other circumstances.

Just a thought, is anyone prepared to bet that all the Brown, Black and Grey wires throughout the UK are connected to the same phase combinations?

Another thought, given three unmarked identical brown wires, is it possible to work out which one is Brown, which is Black, and which Grey.

Dave

As cables in WW2 had all sorts of standards or none it was found that a red cable was included in most cables so the plant I trained in as an electrician settled on using red as the earth. I started my apprenticeship in 1972 and encountered a heater with a red earth in 1974, unfortunately is was still a possibility to encounter this so I had been warned of this. It was also not allowed to be left in this condition and would be correctly rewired.

Mike

I got caught out the first time I came across the US colour conventions for single phase (in a South Korean power station).

It's obvious that white would be live and black would be neutral isn't it?

Turns out that it's white for safe and black for dead (due to electrocution)...