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Any Pointers on electrical layout for a fabrication rig
Former Community Member
Trying to find the best approach to this problem has the cable trays between the sockets of the units will not cater for large cables above 25mm2 so was looking at having to change the design from a looping cabling system between Main sockets on each floor there are 4 floors in total on the rig to each Power Cluster.So that each Power Cluster have there own Power Supply cable going to them individually so we can look at cutting down the size of cabling to fit the cable trays.But to do this i'm after some electrical layout ideas from the Forum.The starting point of the electrical layout are 3 125A Sockets (ie.400v,230v & 115v) which have an interconnection at two ends (ie Left Side and Right Side) so there is a need for a change-over switch.Then from there on looking at adding a large distribution box for the individual cables to connect to the various sockets of the Power Cluster.
The idea of the rig is that it can be moved about so work can be done on different areas and the power supply is plugged in from a form of extension lead that is connected to a main power source in a different building. But because of lack of space within the structure was looking at using smaller cables coming from a distribution box. Did you do a diagram showing how you think it should be laid-out for any pointers going forward?
Loads in total at anyone time would be 4 Welding Machines each producing 16kW of power so in total about 92A.Then there are Milling and Cutting Machines but these won't be used while welding is being done.There is a Crane on the top floor but this produces maximum of 20A this is the 400v system.The 200v system is for the office on the ground floor containing 12 32A Sockets with 4 on the left side and 9 on the right side with workbenches either side and lighting comprising of 12 26W lights and a single light in a changing room.There is presently nothing being used on the 110v system but client wants a requirement.
So this is a mobile 4 stage building - like a stack of portacabins as a mobile worklshop ?
The biggest problem with plugging into supplies unknown is verifying that the earth impedance is OK to clear the fault protection, the fault protection is correct, and also, in the case of the 3 phase extension leads case, that the phase rotation and L_N polarity is correct.
I have some experience of military shelter sort of things that can be dropped anywhere, and in those there is normally a single box where power is marshaled before going out to the equipment, and at this point there are phase rotation indicators, N-E offset voltage trips, and an an earth fault relay . And an all pole isolator.
Power of opportunity is just that, and if you have no idea how it is being connected - and in some parts of the world it could look like jump leads from overhead lines, you have to be robust against all credible faults before you flick the big switch and connect your own expensive loads.
Equally if it is being installed in the UK as a semi-static site, it is not unreasonable to ask for an electrician to hard wire your tails into the local distribution board - after all very few places will have a couple of unused 125A sockets in a handy location, so if they are fitting them specially , then a box with some terminals for hard wiring is probably easier. - that may be as basic as line taps on a paxolin panel or henley blocks, but l inside a large metal box rigidly mounted to the wall or a pillar.
if it was, I'd assume it would have built in induction genset, capable of running on anything from jet fuel or biodiesel to heating oil, with a foamed filled tank, to survive attempts to blow it up by taking pot shots at it. Such things almost exist, as field workshops, but they are more like interconncted bungalows and they arrive on articulated lorries with run-flat tyres, and this does not sound anything like it.
All the structure is,is a temporary structure used for Welding and Cutting Metal within a Oil and Gas enviroment and within it this contains an office with workbenches and all we are after is an idea as to the best approach to cabling up the structure with the loads that go with the unit, has best trying to cut down in size of cabling for ease of fitment to each Power Cluster has the idea of interlinking the power clusters with one big cable for the 400v system seems a tough job with regards to bend radius on the cables.So was looking at giving each Power Cluster there own Power feed if this desirable?.
Temporary structure does not mean it has to be plugs and sockets, and it looks like you need more juice than just a 125A socket can supply.and much above that it gets very awkward to move very quickly, so we tend to use singles like these rather than multicore cables. Carrying more than a few metres of 35mm2 HOR 7 extension lead like this and you will do yourself an injury. We'd pay out off from a landrover or similar for a 25m length.
The scenario is that the bigger cables that are looped in between the Power Clusters will require big bend radius and the total current capacity at anyone time should be under 100Amps (ie 4 Welding Machines) which in essence could a cable of 25mm2 cope ok with. But if each Power Cluster is connected with individual power requirements could reduce the cable size down even more if connected via a distribution box.The 125A Sockets (these being the biggest sockets we can gain commerically) are for the incoming power requirements from the outside Main Power Supply (which has a maximum Power requirement of 250A) to the Rig.Jimmy
Did you look at my link above for the 200A and 630 A sockets ? Or the powerock connectors , available various versions but the 400A ones are very common for this sort of thing..
If you must use 125A plugs and sockets, then have 2 circuits and do not join them to a loop.
I still cannot see the advantage in having a plug in thing, when the sockets to plug it into will have to be installed specially for the occasion, and you have no control of the ADS provision (fuses, breakers RCDs or whatever,) that protect them, so you will need to provide your own . Plug in things at these current levels need as much effort as hard wired tails, and the cables to and from the plugs and sockets are going to be impossible to move if they are more than a few metres long.
