Discuss Single phase power all thats avaiable for new workshop build in the Electrical Forum area at ElectriciansForums.net

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Hello Everyone, new to the forum and looking for some advice on a new workshop, i'll explain.
I am planning on building a metal / woodworking workshop (mainly aluminium and stainless steel) for boat work, refurbishment and boat building.
I am a marine engineer to trade and i am planning on starting my own business doing this in said shed.
Now to understand what i will need for this machinery wise, obviously welders, pillar drill, lathe, press brake, guillotine, grinders, table saw, band saw, and anything else you may think on from grinders to anything else with a maximum of 2 people working separate machines at any given time. mostly just be me on my own.
Now the problem is where the shed is going there is no 3 phase within a mile of it. I can get a single phase 100A supply easy enough but not sure how that will work. Basically just wondering if i will get away with a single phase 100A supply and if i end up with 415v 3 phase machines then i can get an RPC which you can get up to 30hp now, The only other issue there is the 30hp rotary converter is 100A so in theory if the RPC was working to capacity that would be all of the capacity on the network. but to be honest looking at the size of motors in the machines i am looking at 10hp seems to be the max. so even with 2 of them there would be still plenty of spare capacity. but im stilll not sure if it is the right way to go.
What are your thoughts on this? the 3 phase would be wildly costly 50k upwards to install so that's out, i could buy land and put the shed elsewhere if it cannot work going forward but i would like to know your thoughts on this.
The land the shed is planned to go on is ours so it will work out a lot cheaper to put it there, just the issue of supply.
Thanks in advance
Robert
 
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littlespark

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Have you spoken to your supplier or network?
If there’s single phase, I would reckon there’s 3 phase underground or on pole somewhere that’s sitting redundant.
 
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  • #3
Have you spoken to your supplier or network?
If there’s single phase, I would reckon there’s 3 phase underground or on pole somewhere that’s sitting redundant.
Hi
The 3 phase ends about a mile away from where this is, its in quite a remote area in Shetland and the poles there only carry 2 cables. about a mile further back there are 3 phases on the poles and they end at a transformer at a housing scheme.
So the supplier said to get a 3 phase supply installed would mean them adding a 3rd cable from there to my property and then a new 3 phase transformer etc.
So he reckoned when i spoke to him it would be more than 50k to do this.
Thanks
Robert
 

R-fur

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I would go with the single phase supply. If you need three phase for certain machines you can get electronic speed controls that will drive a three phase motor from a single phase supply. I would keep clear of rotory convertors.
 

Spoon

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How are you heating up this shed in winter?
You need a list of the equipment you will be using along with power consumption ratings for the items. This will give us a better idea.
 

Lucien Nunes

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the 30hp rotary converter is 100A .....10hp seems to be the max. so even with 2 of them there would be still plenty of spare capacity.
30hp = 22.4kW mechanical power output. If the motor and converter were both 100% efficient and had unity power factor the line current at 230V would be 22400/230=97A. But they are not. In practice the running current of a 10hp single-phase motor is around 50A so the converter will need at least that. Starting is a different matter, direct-on-line starting can require up to 5x rated current for however long it takes to accelerate the load. Motor performance may also be reduced when running on a converter-derived supply.

If you really do have individual loads that heavy, the 100A supply would be very marginal. You would need to look at voltage drop - you don't want things cutting out every time you start one of the big machines. The biggest loads might be best retrofitted with separate inverter drives as R-fur mentions, with perhaps a smaller general 3-phase supply from a converter. You would get better machine motor performance with lower running current and much more flexibility in limiting the starting current.
 

davesparks

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If this is a new business which you are intending to grow then it would be worth looking at the long term view. Is it better to make the investment now to get the supply you need for the future rather than trying to have the supply installed in a few years time?
Once the business is up and running the inconvenience of having the power installed later and the timescales involved in getting it done could be problematic.

If the business plan is good and viable then you should be able to get business finance to set it up properly.
 
As above

If this is a long term venture , pay the money now and get a 3 phase supply run in.

Think of it as a short term pain 'financially' for long term gain
 

Midwest

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Have you enquired about financial help from the Shetland Islands Council, that they publicise?
 

telectrix

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could always convert to steam power. :dizzy::dizzy::dizzy:
 

Strima

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As it's the Shetlands what about renewable energy such as wind or solar?
 

telectrix

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  • #14
As above

If this is a long term venture , pay the money now and get a 3 phase supply run in.

Think of it as a short term pain 'financially' for long term gain
I would look into this but i have been informed this morning that it would be far more costly than i even expected, would need a full new overhead powerline system down to the location of the shed, so to be honest if going down that route i would be far cheaper building it somewhere else.
 
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  • #15
30hp = 22.4kW mechanical power output. If the motor and converter were both 100% efficient and had unity power factor the line current at 230V would be 22400/230=97A. But they are not. In practice the running current of a 10hp single-phase motor is around 50A so the converter will need at least that. Starting is a different matter, direct-on-line starting can require up to 5x rated current for however long it takes to accelerate the load. Motor performance may also be reduced when running on a converter-derived supply.

If you really do have individual loads that heavy, the 100A supply would be very marginal. You would need to look at voltage drop - you don't want things cutting out every time you start one of the big machines. The biggest loads might be best retrofitted with separate inverter drives as R-fur mentions, with perhaps a smaller general 3-phase supply from a converter. You would get better machine motor performance with lower running current and much more flexibility in limiting the starting current.
I have had a look at each of the machines i would probably need, the biggest motor on any one of them is 7.5kw, i can be 90% sure that i would be using only one of these at any one time and maybe an inverter welder at the same time running on the 240v side.
it is a 23kva supply they SSE guy i spoke with said and he reckoned it would be more than adequate for what i am using it for.
The other possible option i thought of was having 2 seperate 240v single phase supplies installed,
as far as inverters go, would you need one for each machine? to let you know i am planning for most of the gear to get 240v stuff, this can work with a lot of it. but lathe, press brake and guillotines are hard to come by in single phase so it would be them i would need the 3 phase for. so maybe seperate inverters and converters is the way to go.
Are the rotary ones just no good or why dont you reccomend them?
thanks
 
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