It is currently 18 Dec 2017, 15:52

Three phase: what's the story?

Here's the place to talk about all your table saws, bandsaws, routers and dust extractors. In fact anything that makes noise and uses electrickery.

Three phase: what's the story?

Postby Mike G » 03 Sep 2017, 22:50

There is a three phase supply on a pole about 8 or 10 metres from my workshop, on my neighbour's farmland. What is involved with bringing 3 phase into the workshop? Is it just a single armoured cable and some sort of consumer unit, or is there more to it than that? What happens to the lights and sockets that I want to be single phase? I'm told that the overhead cabling is 415 volts. Does that mean I need a transformer?
User avatar
Mike G
Old Oak
 
Posts: 3234
Joined: 30 Jul 2014, 22:36
Location: Somewhat less of a hovel
Name:

Re: Three phase: what's the story?

Postby kirkpoore1 » 04 Sep 2017, 04:41

Mike G wrote:There is a three phase supply on a pole about 8 or 10 metres from my workshop, on my neighbour's farmland. What is involved with bringing 3 phase into the workshop? Is it just a single armoured cable and some sort of consumer unit, or is there more to it than that? What happens to the lights and sockets that I want to be single phase? I'm told that the overhead cabling is 415 volts. Does that mean I need a transformer?



Mike, I'm on the wrong continent, but let me be the first to say "You lucky dog", and yes you'll need a transformer. If I could get 3ph from the pole I could get rid of my phase converter and most of my VFD's.

Beyond that, I'm sure you'll need some kind of service box that will feed your existing consumer unit (what we call a breaker box) with two wires of the 3ph to give you single phase service. Others will no doubt chime in with specifics.

Congratulations!

Kirk
User avatar
kirkpoore1
Nordic Pine
 
Posts: 677
Joined: 21 Jul 2014, 22:12
Location: O'Fallon, Illinois
Name: Kirk

Re: Three phase: what's the story?

Postby RogerS » 04 Sep 2017, 05:00

Bob's your expert on this but until the 'late shift' logs in...

yes...an armoured cable which will terminate in something like this

Image

No, you don't need any transformers. If you connect a pair of wires between neutral and one of the phases you will get 230v.

My one concern is the statement that 'the overhead cabling is 415 v'. This means that the transformer converting high-voltage 11kv or 22 kv 3-phase incoming from the electricity supplier's distribution cable down to the 415v three-phase mains cable is somewhere (probably up a pole). Do you know where each end of the overhead cable is located and what they are connected to? Is the person who told you that it is 415v sure of this ? This cable could be fed from AFTER the farm's meter in which case you'd have some tricky negotiating to do with the farmer re billing your consumption.

You also have to balance the load on the three phases but a spark should be able to advise you on that and everything else.
Fewer Smart things. More smart people.
User avatar
RogerS
Old Oak
 
Posts: 4167
Joined: 21 Jul 2014, 21:07
Location: Please God. Make it stop raining.
Name:

Re: Three phase: what's the story?

Postby old » 04 Sep 2017, 08:14

High voltage is used to distribute over distance then transformed to lower voltage for local distribution 3 phase. So a housing estate say has a cable with neutral and three phases each 230volts with respect to neutral, houses 1 to 3 get connected to phases 1 to 3 and so on to even out the load . If you require a 3PH supply then its high voltage transformed to 3PH cabled into your installation the distribution terminates all three phases and neutral so you have 3 x 240v and/ or 3 x 415v . The 415 is between phases yes 240+240 is not 415 this is where the maths comes in just accept it .So the cable with 4 conductors supplies 3 times 240v and a neutral to the machines .This installation will require metering for all phases .Also one of the phases could be extended to provide power to the main dwelling and recover existing feed.I have tried to keep it simple not mentioning star and delta connection as you are not requiring industrial type power
Last edited by old on 04 Sep 2017, 16:11, edited 1 time in total.
User avatar
old
New Shoots
 
Posts: 59
Joined: 27 Jul 2014, 07:20
Location: Nantwich Cheshirre
Name: Chris

Re: Three phase: what's the story?

Postby Jimmy Mack » 04 Sep 2017, 11:58

Mike G wrote:There is a three phase supply on a pole about 8 or 10 metres from my workshop, on my neighbour's farmland. What is involved with bringing 3 phase into the workshop? Is it just a single armoured cable and some sort of consumer unit, or is there more to it than that? What happens to the lights and sockets that I want to be single phase? I'm told that the overhead cabling is 415 volts. Does that mean I need a transformer?



You first port of call will be to call POWERGRID or whoever owns the supply line. I filled in a request via Northern Powergrid's website, it was quite easy.

They'll contact you with an estimate, (usually quite under!) then provide a final quote to book in.

They'll come out and connect a supply cable and install a 3 phase cutout (the bulky fuses 80-100A) to the closest point/ meter cabinet on your property (they choose location, usually) You then contact an energy supplier (Sainsbury's, British Gas, etc, etc) to install a meter (FOC) so you can be billed and have something to connect to.

Now you and your sparky are ready to connect a consumer unit/ distribution panel to the meter.

If the meter is away from the workshop (e.g. lets say a box on the boundary of your property) then your sparky would install a fused switch (box with an isolation kill lever/switch) here and you would run some 4 core SWA with an separate EARTH to the workshop and distribution panel. With the diameter of the cable being based on distance run. Mine is 25mm as it's running 50meters (voltage drop). I'm not sure if the fused switch is mandatory, your sparky would know, It does protect the 3 cut out fuses.


In your workshop distribution box you'll have 3 phases L1, L2, L3. All your single phase domestic style supplies (lights, ring, heaters,) will tap into any ONE of these. Your 3 phase machines will use all three.


In my case my 3 phase 'cut-out' also supplies the house ....my house connects to L1....my workshop lights and ring are on, L2 & L3, and my workshop machines are on all three L1,L2 & L3. This is so the supply is balanced. A good sparky should ask about all the things you are planning on running and calculate this for you.

It cost me £3000 to have 3 phase run 7m across the road and a cut out installed on my property (which is right next to the pavement). Any works on your property have to be prepared by yourself before. The requirements are usually explained before hand.

HTH....Maybe too much detail :lol:

Jim
User avatar
Jimmy Mack
Nordic Pine
 
Posts: 649
Joined: 21 Mar 2016, 19:04
Location: Leeds, West Yorkshire
Name:

Re: Three phase: what's the story?

Postby RogerS » 04 Sep 2017, 12:01

Great post, Jim. :eusa-clap:

(Roger...who is a bit mithered at the moment as the incoming voltage is 240v as opposed to my transformer tweaked 255v on a good day.). There was a major power cut yesterday evening and I'm hoping that it's a result of that and only temporary.
Fewer Smart things. More smart people.
User avatar
RogerS
Old Oak
 
Posts: 4167
Joined: 21 Jul 2014, 21:07
Location: Please God. Make it stop raining.
Name:

Re: Three phase: what's the story?

Postby Mike G » 04 Sep 2017, 12:17

Thanks Jim. Great post, and a really useful explanation.
User avatar
Mike G
Old Oak
 
Posts: 3234
Joined: 30 Jul 2014, 22:36
Location: Somewhat less of a hovel
Name:

Re: Three phase: what's the story?

Postby Jimmy Mack » 04 Sep 2017, 12:24

Thanks Roger

Here's a post support (rough) diagram.

Image

Image

And the workshop distribution board... You can see the 3 phase machines using all three phases, and the 240 stuff just taping into one phase. Of course L1 is not used by the 240v stuff, as the household DB is busy on this

Sent from my Moto G (5) using Tapatalk
User avatar
Jimmy Mack
Nordic Pine
 
Posts: 649
Joined: 21 Mar 2016, 19:04
Location: Leeds, West Yorkshire
Name:

Re: Three phase: what's the story?

Postby Robert » 04 Sep 2017, 14:13

Think it has all been explained and I've only skim read all of the above.

Between each pair lines is 415V but each individual line is 240V above earth. The higher voltage between 2 lines comes from them being out of phase by 120 degrees. You don't want to wire between live and earth so you have a neutral wire instead for 240V. I think the neutral is bonded to earth back at source. At the house it can be a couple of volts above earth due to voltage drop in the neutral return.

At the factory we had to keep the single phase loads on each phase balanced. 3 phase loads are by their nature equal on each phase but we had to make sure the power factor was corrected properly. Motor loads draw current and shift it out of phase with the voltage. that means V x I does not equal power. The wiring will only take a certain current so you want it all in phase with the voltage. That means power factor correction is required. Doubt you'll have any of those problems with a domestic load :)
Robert
Old Oak
 
Posts: 1167
Joined: 21 Jul 2014, 19:31
Location: Woodford Green
Name: Robert

Re: Three phase: what's the story?

Postby Deejay » 05 Sep 2017, 10:06

Morning Mike

Is the supply shown on the fifth picture on page 2 of your workshop thread ?

viewtopic.php?f=35&t=198&start=25

If so, it looks like a high voltage line which will feed a transformer on the grid. You would need a supply from the low voltage side of the transformer.

The power company might be able to fit a transformer on the pole, which may need replacing if it isn't strong enough to carry the additional weight. I assume that you would have to pay all their costs.

If there is a three phase low voltage distribution in the road (overhead ?) it might be cheaper to have a supply installed in the house and feed it from there to the workshop.

Talk to the supplier to see what is possible.

If all else fails, you could install an inverter.

Cheers

Dave
User avatar
Deejay
New Shoots
 
Posts: 207
Joined: 22 Jul 2014, 09:36
Location: Wiltshire
Name: Dave

Re: Three phase: what's the story?

Postby Mike G » 05 Sep 2017, 11:08

Yep, that's right. That pole is just a few metres from the workshop. I'll enquire with National grid and see what's what.
User avatar
Mike G
Old Oak
 
Posts: 3234
Joined: 30 Jul 2014, 22:36
Location: Somewhat less of a hovel
Name:

Re: Three phase: what's the story?

Postby RogerS » 05 Sep 2017, 11:15

Mike G wrote:Yep, that's right. That pole is just a few metres from the workshop. I'll enquire with National grid and see what's what.


Mike, I think you will find that it is not the National Grid but

http://www.ukpowernetworks.co.uk

who cover your area.
Fewer Smart things. More smart people.
User avatar
RogerS
Old Oak
 
Posts: 4167
Joined: 21 Jul 2014, 21:07
Location: Please God. Make it stop raining.
Name:

Re: Three phase: what's the story?

Postby Mike G » 05 Sep 2017, 13:23

Yeah, I knew that.... I know a UKPN employee locally who would do this in his spare time for vastly less than going through the normal channels.......if the paperwork is OK, which it won't be.
User avatar
Mike G
Old Oak
 
Posts: 3234
Joined: 30 Jul 2014, 22:36
Location: Somewhat less of a hovel
Name:

Re: Three phase: what's the story?

Postby RogerS » 05 Sep 2017, 13:28

Mike G wrote:Yeah, I knew that.... I know a UKPN employee locally who would do this in his spare time for vastly less than going through the normal channels.......if the paperwork is OK, which it won't be.


Not a chance. You're looking at a disconnection of service to 'x' properties or a 'hot glove' team.
Fewer Smart things. More smart people.
User avatar
RogerS
Old Oak
 
Posts: 4167
Joined: 21 Jul 2014, 21:07
Location: Please God. Make it stop raining.
Name:

Re: Three phase: what's the story?

Postby Duncan A » 09 Sep 2017, 13:23

Robert wrote:You don't want to wire between live and earth so you have a neutral wire instead for 240V.


Sorry, this is a pet hate of mine...
"L" stands for Line, not Live
"N" stands for Neutral
Both "L" and "N" are likely to be live!

I'm sure all contributors to this topic understand these terms, but casual readers may not, and use of the terms Live and Neutral together may imply that only one of them is likely to bite! Of course, those that don't know what they're doing should not play with electricity, but the reality is that we all like to learn how to do things and have a go ourselves.

Duncan
Duncan A
Seedling
 
Posts: 4
Joined: 09 Nov 2016, 17:31
Name:


Return to Machines & Power Toolery

Who is online

Users browsing this forum: No registered users and 2 guests