Looks a squeeze, 240 swa thoughts.

[ksa74f]

Plus 1 for a parallel feeder

 

[LeeH]

I will have to look again, but I don't think 2 95's quite cut it IIRC.

This install is in Spain so the ambient temps are higher than blighty.

 

[westward10]

If a 240.0 is adequate 2 x 95.0 should be okay as it should give an improved ccc of 10 to 12%.

 

[Darkwood]

Something doesn't ring right about this thread, firstly we need to know how the motor is going to be started and connected, can we get a pic of the plate here and then go on from there, if we have a star/delta arrangement then the csa of cores can be reduced, from experience they do not make motor connections that are impossible to connect to whether it be space or terminal arrangement, if this seems the case then we have missed something out here.

PS - where did 240mm cable come from?, first mentioned in post 6?

 

[LeeH]

Can you reference that somehow please Westy?

I have never done a manual/paper parallel cable calc.

 

[Bobster]

How about 2 x 120mm?

They'll go easy into that.

Edit: most likely be connecting in delta, so it'll fit lovely. An if cable calcs for 1 x 240 is ok, 2 x 120 will be better still.

 

[westward10]

It was a basic calculation based on your 240.0. From Tables 4D4A and 4E4A whereby you half the ccc of the 240.0 and find the nearest csa to that rating which is 95.0, double the ccc of two 95.0s and this is 10 to 12% greater than the single 240.0.

 

[LeeH]

Something doesn't ring right about this thread, firstly we need to know how the motor is going to be started and connected, can we get a pic of the plate here and then go on from there, if we have a star/delta arrangement then the csa of cores can be reduced, from experience they do not make motor connections that are impossible to connect to whether it be space or terminal arrangement, if this seems the case then we have missed something out here.

PS - where did 240mm cable come from?, first mentioned in post 6?

Hi Darkwood, its a VFD as mentioned a few posts down.

I will dig out the data sheet tomorrow.

Amtech cable calc.

 

[Darkwood]

Of the top of my head I cannot see you needing anything larger than 70mm paralleled up using single core tri-rated, assuming distance not an issue here from VFD to motor if distance is what is causing you to increase CSA then it is that you need to address, there are options of how to do this but also with distance on VFD outputs comes other issues like Harmonics?

How is the final connection to the motor configured is it star or delta?

 

[westward10]

Of the top of my head I cannot see you needing anything larger than 70mm paralleled up using single core tri-rated, assuming distance not an issue here from VFD to motor?

Too small once you apply grouping factors.

 

[Darkwood]

Too small once you apply grouping factors.

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

 

[timbobelfast]

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

 

[westward10]

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]

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]

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]

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]

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]

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.

 

[Darkwood]

@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]

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?