3 phase supply variations

[Joel OF]

Hi folks, any chance that someone with a bit of 3 phase knowledge can offer me some advice? At the minute my knowledge of electrics is a bit woeful, I'm afraid.

In a few months time I'm meant to be relocating my workshop to a disused farm barn. At the minute the barn is in a bit of a state so the farm manager is hiring a builder to make it usable, one major aspect of the work will be extending the 3 phase supply from a nearby shed into the barn. Once the 3 phase has been extended into the barn and fuse board has been put in it'll be my responsibility to hire and electrician to locate lights, power sockets etc.

The farm manager and his builder, my electrician and me are all meeting early next week to discuss the work involved. The thing that's making me slightly nervous is that I met up with the farm manager and builder the other day (without the electrician) to locate the 3 phase supply and when the builder saw the cable he said it didn't look that big (black in colour and about 1 inch in diamter). This made me wince a little because in my naivity I thought all 3 phase was the same, but from what he suggested it might not provide as much juice as I expected.

When we all meet up next week my electrician is bound to ask me how much power I'm going to need to run my tools. That's where I fall flat on my face because at the minute all my gear in single phase and I don't know what sort of strain I'll be putting on the supply when I do finally upgrade to 3 phase tools. In the future I expect I'll want a reliable compressor for painting and a bit of blasting, a big drill, a small power hammer and a decent MIG.

I'm not asking for exact power consumption figures of these tools, but I'd really appreciate it if anyone can give me some general information about the day to day running of these tools that the electrician may find useful. I expect he's going to ask something along the lines of "what kind of supply do you need to be able to run a small power hammer, a single phase forge blower, a grinder and lights at the same time?" or something like "what kind of supply do you need to continuously run a compressor for spray painting for an hour?"

A fabricator mate tells me his workshop is rigged up this way: 13 amp single ring main, 3 phase individual circuits and a separate 240v supply which he runs a 110v transformer off. That seems like a tried and tested setup that's worth copying if appropriate. I expect in the future I'd want four 3 phase sockets.

Sorry that's all abit vague but if anyone can offer any general info the electrician may find helpful I'd really appreciate it. All I really need to be able to do is help the electrician determine whether the 3 phase supply that's available is up to the job. Cheers.

[turbo7]

The biggest unknown will be how much growth you expect? When you finally work everything out in only a few years you will at least want double what you need now, if you are planning a long stay expect to want tripple the power you want now. This may seem unrealistic atm, and while costing you extra, now is the cheapeast time to increase the cable size and the switchboard size.

[Joel OF]

Yeah, true.

Sorry, I should have added that the cable was overhead.

[turbo7]

Get a list of the amperage of your gear, and gear you want, work out how much use you expect, what items will possibly be running at the same time, wheather running continuos or only part time. Dont forget lighting especially any flood lighting.

[ironwolfforgeca]

here in the USA most small shops are wire for 200 Amps -- in put -- IF they can get that ?? or more from Main Lines

a 100 amp would be minim ! that I would do -- talk to you're electrician & power Co !!!! & see how much you can get ???

its way better to be over powered than under -- cost here is about the same no mater what you do

my shop 40' x 60' is 3 ph 240 & 400 amps lots of power to spare also lots of room for another building

just can't afford to build it    & 3 ph is not that hard to wire --

I have a Delta leg into shop thats 2 - 120 volt lines +  the Wild leg this one verys from 120 to 208 volt if I remember right

NOW this in the USA & may not be the same or close over there LOL

you remember wrong if 2 are at 120vV ratings then the high leg is 240v

[Alan Evans]

It is not so much what your compressor uses in an hour as the load it requires for start up.

All you machines will have motor plates with their rating, make a list to show your electrician.

One thing that saved me a few tens of thousands was writing a letter to my electricity company asking if the forge supply would cope with a 24hp motor on my power hammer and a 500 amp (can't remember the load off hand) mig welder. They wrote back and said yes, just don't start the hammer while the mig is in use or more than four times per hour. A few years later when my neighbours complained the hammer was pulsing their lights the power company were threatening that I would have to pay thousands for a new transformer or a bank of capacitors or stop using the hammer. When I mentioned their letter of approval they funded the 100kVA transformer and new 120metre direct to the forge underground power line themselves…phew!

I don't think they knew what a power hammer was so did not factor in the pulse effect.

Alan

[Steve Sells]

the electrician will need FLC and running amps of all your motor loads, square footage and lighting,  A/C and Heating if any,  he will know what to look for.  Try to take what many here in the USA comment about what amperages they use here with a grain of salt.  Voltage of the lines are differently here so 100 amps on 120 volts here would be close to a 50 amp line on 230 volts, 30 on a 380 volt.   Dont really worry about it. make sure you are not lower than demands based on present load, and talk about your plans for future expansion, and you will save money by doing it right the first time. 

FYI 1 inch is not a wire size, If you at talking the copper wire with insulation coming in is about 1 inch diameter that is about 350 MCM and that is good for 350 amps power each leg.

If you hired a good electrician, then trust him to know what to look for on your needs, if ya dont trust him, get another one .

 

[ianinsa]

Joel, many a small factory will have a 60a 380v supply and I guess it'll be more than adequate and a 1" armored cable will probably cope if only just if it isn't going to cost you an arm and a leg it would be best to get that upped. What's important is to get your phases balanced that will keep the max demand (and your bill) down.

[Joel OF]

Thanks for the replies folks. A gerbil on a treadmill would power the gear I've got at the minute but I can nip round some mates places and scribble down the power requirements of some of their 3 phase tools which I'll possibly want in the future (drill, compressor, MIG, plasma cutter etc) but the thing I'm hitting a dead end with is the juice requirements for a small power hammer. Can anyone help with some educated guestimates? I've tried Googleing Anyang power hammers as a starting point but it seems their UK distrobutor(?) isn't doing them anymore so I can't get any info on them, and I've really annoyingly misplaced (i.e my girlfiend has "tidied them up") my copies of BABA magazine which have the details of single phase power hammers for sale in the ads section.

[ianinsa]

A reasonable hammer (I don't know about Anyang) will need about 10kw 380v  3ph that is enough to run my 200kg De Moor

Edited August 15, 2015 by ianinsa

[BIGGUNDOCTOR]

Long post lost.......grrrr.

Here is the short and sweet version.

Welders and plasma cutters are mostly single phase. There are some big industrial units like myMiller MP65E that are 3 phase.

The higher the voltage the less amperage. 100a on 240v is only 50a on 480v, double the voltage halves the amperage.

In my shop the only three phase equipment were the lathes, milling machine, surface grinder, the  big MIG, and a 14" pedestal grinder. Drill presses are usually single phase unless you have a really big industrial , or a radial drill.

Compressors are good candidates for 3 phase.

 

 

[tzonoqua]

Hi Joel,  you are wanting to speak to John Nicholson, he's on here I think as John N, he's the Anyang dealer here and a really helpful guy. Also don't limit your future to small... think big

[gote]

I assume that you have the same kind of grid as we have in Sweden: three phase 400V . In your setup you will have three lines (phases in my language) neutral and ground, hand tools small motors and lighting is 230V. This you get between one of the phases and neutral. A typical socket or lighting fixture is thus connected to neutral and one of the phases (plus the chassis, if metal, to ground as safety measure). The installing electrician will try to distribute your 230V loads evenly between the phases so the neutral remains (nearly) neutral. Ideal neutral has the same voltage as ground i.e. zero but this is not perfectly achievable. To find the Amps consumed by a 230V appliance, divide the power in Watts by 230. (or multiply kilowatts by 4.3). If you are running three 5-kW motors (6.7 hp) from the same socket, you will draw some 60 Amperes and need that supply. If you are putting them in different sockets connected to different phases you will need only 20 Ampere in each phase. This will be considerably cheaper to install and cheaper on your bill. Thus it is important that you and a skilled electrician find out the best way to distribute the phases between your 250V appliances.

Larger power consumers run on three phase = three times 400V. (The voltage difference between two phases is 400V). If you have a 400v resistive load like an oven or kitchen range you divide the kW of the appliance by 0.7 If you have 14kW consumption you need thre 20A phases. If you run motors or  transformers (read welders) you have to compensate for that max Amperes is out of whack with max Volts so you have to put on some 20% Thus If you have totally 14kW load you should have 25A input.

Our American friends have another type of system with generally lower voltages. That will force higher Amps. The 200A recommended in a post above will be sufficient to run a 200 horspower electric motor this side of the pond. I think three phase appliances are more common here. The higher voltage means thinner leads in the power lines. A three phase motor is less complicated to build and more reliable.

I hope this is clear enough to be of help.

Göte

 

Edited August 17, 2015 by gote

[Joel OF]

Thanks for the replies everyone. Gote - thanks for the generous explanation.

Well, the 4 of us are meeting this evening on site so fingers crossed. All being well this place will serve me well into the future and give me more than enough room to expand as it's 11m x 6.5m and only £2,500 a year, all in!

[ianinsa]

Good luck!

[Alan Evans]

Sounds a very good deal. Enjoy it.

I have just read your OP again and notice the reference to blasting.

For years I managed with a 5hp compressor. When I bought a shot blast cabinet though, 5hp was not enough. You would blast with diminishing effectiveness for a few minutes then hang around while the pressure built up again. And this was with a pressure pot rather than a suction feed. A 10hp Hydrovane transformed the experience. You just turn it on and blast continuously, no waiting, it took a third of the time and reduced the frustration.

Second hand it was not much more than a new 5hp piston unit.

Alan

[ianinsa]

Alan , you lucky little bead blaster here you got to give them at least one arm and a promissory note for at least a foot if not the whole leg.  

[the iron dwarf]

50kg sahinler ph 7.5hp, about 5kw.

here in the UK you can get better kit cheaper if you have 3 phase, a good welder or plasma second hand of double the size you can get in single phase will cost half the amount the smaller single phase one would cost

[Joel OF]

Thanks again for the input folks.
I think the meeting went well though some of it went straight over my head. The electrician has asked me to email him a list of all tools I'll want in the future and said he's most interested in the kw specs.
There seemed to be 2 boards in the shed where the 3 phase enters the farm, the first said 100amps but was already quite full and the electrician said he didn't feel comfortable coming off that. The 2nd board seemed to be an auxillary of some sort that was fairly empty, he said he could come off that and run me a supply of about 50amps.

Does that sound sufficient bareing in mind I'm a one man band that will only be doing lightweight forging and fabrication within the next 5-10 years? It'll probably be 5 years before I can afford a bloomin' power hammer!

[the iron dwarf]

you wont be using all the tools at the same time so 50 should be plenty, that is 50a per phase at 415v for those who dont know

[gote]

Agree. Fifty is plenty. If you work alone, I would  assume 25A (three-phase) to be enough. In my corner of the world,the electricity bill is a mixture of actually consumed power and maximum supplied power. The grid may be designed for a 50A input but if I have 25A fuses in the meter I pay for 25.

Good Luck

Göte

[Alan Evans]

Alan , you lucky little bead blaster here you got to give them at least one arm and a promissory note for at least a foot if not the whole leg.  

Reminds me of yet another awful cruel skuleboy joke…and not R. Molesworth this time… actually I deleted the awful joke it was too awful...

Alan

Edited August 19, 2015 by Alan Evans

[SmoothBore]

Due to the variables in International Power Supplies, ... and trying to cope with the wide range of available Voltages and Megahertz ( frequency ), ... it's more consistent to reduce everything to Watts, or Kilowatts.

In the end, you aren't billed for "Volts" or "Amps", ... for the purpose of billing, the universal standard of measure, is Kilowatt Hours.

Therefore, Electrical Engineering "standards" are routinely referenced in Kilowatts ( Kw ).

That way, you know everyone is "on the same page".

 

.

Edited August 22, 2015 by SmoothBore

[Alan Evans]

Due to the variables in International Power Supplies, ... and trying to cope with the wide range of available Voltages and Megahertz ( frequency ), ... it's more consistent to reduce everything to Watts, or Kilowatts.

In the end, you aren't billed for "Volts" or "Amps", ... for the purpose of billing, the universal standard of measure, is Kilowatt Hours.

Therefore, Electrical Engineering "standards" are routinely referenced in Kilowatts ( Kw ).

That way, you know everyone is "on the same page".

 

.

Quite agree with the sentiment, but we are not on quite the same page with the acronym.

i always understood it was kW. Lower case "k" capital "W"

maybe be that is just over this side of the Atlantic.

Alan

[turbo7]

What upper/lower case do you use for other measures Alan? In Aust the first letter is upper case and second letter is lower case.