Looks a squeeze, 240 swa thoughts.

Darkwood · Jan 12, 2018

westward10 said:
Too small once you apply grouping factors.

Expand on your grouping factor, why would you be applying it here?

timbobelfast · Jan 12, 2018

That's a lump of a motor, is it Ex d or n. Assuming the hazard is dust rather than gases?

westward10 · Jan 12, 2018

darkwood said:
Expand on your grouping factor, why would you be applying it here?

Ccc for tri rated are generally for a single conductor in free space, apply six of them and assuming they will not be separated in free space grouping factors should be applied.

Darkwood · Jan 12, 2018

westward10 said:
Ccc for tri rated are generally for a single conductor in free space, apply six of them and assuming they will not be separated in free space grouping factors should be applied.

I wasn't trying to trip you up, the cores would generally be grouped into 2 standard recommended tri formation and spaced apart thus minimal grouping factor, the 30m ladder run can account for all the sizing, grouping issues but the final connection only has to be rated for the motor termination, an interim connection unit would be the preferred method and the last link would be in 70mm tri in parallel run in 2 flexi conduits and if delta formation then even better, as each has its own terminal lug, it would of course mean a cable size reduction at the motor but this work falls under machinery control, the VFD protect the cables from overload, the last section (motor link) only needs to be calculated for its limited length and install methods.

Given that the long ladder run is taking the hit for all the grouping etc and is not the final termination to the motor then SWA in parallel is probably a better option there.

PS - just to add as it's running off a VFD it has to be remembered that if tri is used then it still requires a suitable screening method hence the SWA option and flexi metallic conduit to link the motor may be a solution.

westward10 · Jan 12, 2018

Slight cross wires on my behalf I was considering tri rated for the entire run not just the final connection. Nevertheless the two separate parallel connections would require grouping factors for the three conductors which I calculate to 326.6A.

Rocboni · Jan 12, 2018

I would say SY is the best option here, it offers better screening properties than SWA, not sure if SWA can be classed as 360degree screening? depends if compliance with
89/336/EEC has to be met as defined by the standard EN 61800-3. Cable shield should be grounded at both ends.

Can you not move the inverter next to the inverter and supply with a 240mm SWA?

Ive came across inverters where cable length is limited 30M, but never worked on anything this big!

Would a local isolator be required?

Most likely connected in delta if connected to an inverter.

Darkwood · Jan 12, 2018

I was looking at 105c rated if you get high temp lugs and connection unit then all can be done with reduced sizing, also depending on the motor duty and loading it may not ever need to pull full load and many questions need to be asked but I would find it surprising if we are needing over 70 in parallel if the correct equipment is selected, 95mm parallel may be what is needed but just going by info given.

Andy-1960 · Jan 13, 2018

The attached file shows the ways recommended for cabling VSD’s by ABB.
I would not be happy using 105 deg rated cable connected to a motor such as this in a warm environment as the heat from the conductor has to go somewhere and that is usually into the motor which in my experience ends up burning up connections in the motor box.
Also another question to ask is whether the motor is suitable for use with a VSD? Has it been fitted with insulated bearings?
I tend to agree with Rob, 2 x 120mm SWA cables seems to be about right with a seperate earth conductor (not integral).
I do this a lot and regularly install L.V drives on motors up to 550kw in warm environments.

[ElectriciansForums.net] Looks a squeeze, 240 swa thoughts.

Darkwood · Jan 13, 2018

@Andy 1960
The info from Lee is very limited here,
Motor config'
Onsite options (reduce the VSD distance)
Hot factory??? What exactly do that mean
Speed of motor? Is the motor been speed controlled and if so is additional cooling measures been put in place?

I have already admitted the conditions for 70mm high temp tri would have to be favourable and do rely on a few factors like motor duty and VSD setting, also 70mm 105' degree tri has a unity x1 factor at 45degrees although this could vary dependent on manufacturer ... If the motor has temp' protection and high temp' lugs are used and connected to gear also rated then there should be no issues.

I also do a lot of VSD's although hands up not usually this size but I also do machines that have heating banks, elements etc where temp' is a major headache when choosing suitable cables and connections.

Digging out my cable charts I admit 70mm is a bit optimistic and relies on too many favourables but 95mm with a 0.7 grouping wired in parallel in groups of 2 x 3 formation to the motor from the connection box within metal flexible conduit then any other suitable method of appropriate sizing for install methods between VFD and connection unit wouldn't be so far out of the park here.
http://www.batt.co.uk/upload/files/...ulcsacurrentratingstablebec100_1219731558.pdf

timbobelfast · Jan 13, 2018

Only problem being that the motor is certified and has only 2 x 75mm cables entries.
The last motor of this size that I have worked on was 11kV.

Do you have a picture of the motor information plate?

Darkwood · Jan 13, 2018

To be fair and I have touched on this, I would require a hell of a lot more info of Lee before designer the motor power supply, like I said, even something as simple as having speed control could change the requirements of the existing motor set-up and could require the need for force ventilation.
VSD - Motor cabling also has many factors to be considered here, the BS7671 is based on general cables and their common ratings and values, if you come away from these and go into specialised cabling with different insulation and sheath materials then it can open other options which can see reduction in CSA, I use IGUS and LAPP brands which can mean you have to forget the BS7671 charts and use the manufacturers guides.

Andy-1960 · Jan 13, 2018

Darkwood, I agree the info is a bit sketchy and I have not had much to do with ATEX installations. It’s a very onerous minefield in my opinion!
One thing I do recall though is that I believe the VSD and the motor have to be a matched pair in order to comply with the regs.
Something else the OP should maybe look into as well as the requirement for insulated bearings that I mentioned in my earlier post.

Darkwood · Jan 13, 2018

@Andy-1960
You and me both - ATEX is not my field either so will leave comment on that side for others, I am interested in your matched comment, do you mean brand matched or motor is actually matched to the drive on a individual basis.. given the tech' now in VSD's I am somewhat confused by the matched comment?
As for insulated bearings, I was led to believe most modern VSD friendly motors were designed to limit/stop circulating currents through the bearings, agree if it is deemed to be an issue with this setup then it does want addressing.

polo1 · Jan 13, 2018

This topic is outwith my experience, but it’s good to see/read knowledgeable people having a constructive dialogue about the possible issues and solutions.
Just sayin’!

westward10 · Jan 13, 2018

I would assume matched to the motor and not by brand.

Looks a squeeze, 240 swa thoughts.

Darkwood

timbobelfast

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westward10

Darkwood

westward10

Rocboni

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Darkwood

Andy-1960

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Darkwood

timbobelfast

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Darkwood

Andy-1960

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Darkwood

polo1

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westward10

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