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Thread: 2 Phase Power ????
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25th October 2004, 06:51 PM #1Senior Member
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2 Phase Power ????
Have been looking at the possibility of selling in Donvale, and moving down to the Bellarine Peninsula. Looking for a SHED with house, on a bit of land, bigger than the suburban block, so as to not disturb the neighbours with the sound of my machinery.
Have heard of ( and basically understand) the terms Single Phase, & Three Phase. BUT, several of the properties I have looked at, boast of Two Phase Power.
Can any of you folk tell me about this Two Phase ? All of my existing machines are single phase eg Table saw, thicknesser, jointer, dust extracter, most drawing 15 amp.
Or am I getting it wrong from the Agents - is it just single phase AND three phase???
Thanks
mick
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25th October 2004 06:51 PM # ADSGoogle Adsense Advertisement
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25th October 2004, 07:55 PM #2
Our power grids supply 3 phase.
Each single phase is 1 leg of 3 phase back to the Star connection (or common) of the 3 phase source.
2 phase just means you have 2 seperate 240 volt single phase supplies.
Plus you can connect to each of the 2 phase legs and this gives you 415 Volts (single phase as the star connection common is not used in this case)
Some industrial machinery is equipped with 415 volt motors so you can use these.
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25th October 2004, 08:18 PM #3
A mate had a farm with 3 phase power connected to the dairy, bought a three phase combination machine to use in his workshop, didn't operate. Further investigation showed that only two phases had been brought down from the dairy for the 415volt electric Welder.
Net results was additional costs incurred to bring additional phase down from the dairy to the workshop, connection fees etc.
regards
Kev M
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25th October 2004, 08:25 PM #4Registered
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I used to work for a mob years ago that put 480v motors on some machines.
As far as I know 2 phase is 480v, its just 2x240v.
I think it worked like this, 2 active wires @ 240v, one common neautral and one earth.
But dont quote me on this, I may be wrong.
Al :confused:
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25th October 2004, 10:20 PM #5Senior Member
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Mick
What ecnidna says is correct - unless the agents have it wrong! I would just like to stress the point that it is NOT 3 phase - i.e. you can't run 3 phase motors from it.
In our old property we had 2 legs (phases) going to our house, 1 leg to a workman's flat and all 3 phases to my workshop.
Domestically, some stoves and some storage electric heaters are (or were) designed to use 2 phases mainly to better distribute the load.
CheersGeoffS
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26th October 2004, 12:09 AM #6
2 Phase supply was quite commom many years ago as it was cheaper and easier to run the cables. You required 480v motors which were common in a lot of the old daries. Check the supply you could find the external lines going past the property may have been upgraded to 3 phase , the property you are looking at may not have bothered to upgrade.
Something else to consider is the supply to the house or shed. If it is in the old wiring the mains may not be big enough for you to run the modern machines that use a higher starting current.
You may need a total upgrade.Jim Carroll
One Good Turn Deserves Another. CWS, Vicmarc, Robert Sorby, Woodcut, Tormek, Woodfast
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26th October 2004, 10:21 PM #7
G'day.
We have 2 phase in a rural area (the sticks, somewhere near a dairy)....
It comes from a transformer on a SWER line pole. (Single Wire Earth Return)
As far as I know, there is no way to make 3 phase from a single wire
with a transformer. (it needs more electronics)
It is however, easy to make 2 phase from a single phase using a centre tapped transformer.
The main differance between 2 phase from a 3 phase system &
2 phase form a single phase system is that,
in 3 phase, the phases are 120 degrees out of phase, therefore any
2 phases are 120 degrees out of phase & in a single phase system,
the second phase is generated using a centre tapped transformer &
therefore the 2 phases are 180 degrees out of phase.
Now we get even more techo....
the RMS AC voltage across 2 phases of a 3 phase system is 415Volts AC &
480Volts AC accross the 2 phases from a centre tapped single phase system.
Confused???? Good.Cliff.
If you find a post of mine that is missing a pic that you'd like to see, let me know & I'll see if I can find a copy.
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26th October 2004, 10:28 PM #8SENIOR MEMBER
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At least with 2 phase 480v you get to use 5hp plugin or 7.5hp hardwired motors. That is if you can afford the $3.00+ per hour runnings costs. Definately night/weekend rate use.
Oh, and to move these ginormous motors you will need a very strong (dumb) mate or engine crane. The one I have in the shed is seriously heavy.
Ken
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27th October 2004, 06:13 PM #9Senior Member
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Careful here - appears that 2 different things are being talked about.
2 phases - as in 2 phases of a 3 phase supply. That is what I was refering to in my previous post.
OR
2 phases as in 'splitting' one single phase supply as Cliff refers to in his post. On his SWER line (commonly called 'swear' lines!) which is just a single wire (obviously) there can only be 1 phase. You can only get 3 phases out of this by either mechanical methods or large electronic methods. Two 'phases' can appear to be achieved as described by Cliff. However because the 2 'phases' are at 180 degrees, motors etc are no more efficient than single phase motors because they are actually only single phase motors running on 480volts. The total current is still going to zero 100 times per second.
A 5hp or 10hp single phase motor is big big brute whether it runs on 12 volts or 1000 volts.
CheersGeoffS
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27th October 2004, 07:20 PM #10
I thought the three phases were old, new and full, and they rotated around about once a month.
Boring signature time again!
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28th October 2004, 09:01 AM #11Senior Member
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Thanks for your replies - I'm a little more informed, but still confused.
Obviously, I will have a n electrician check out the actual situation, but here's another question for you.
If the power supply is two-phase, can this supply be adapted so single phase machines can be run off it.
By the way, there are fluro lights in the shed, so single phase power must also be there, either independently, or modified from the two phase source ??
Thanks
mick
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28th October 2004, 10:51 AM #12Originally Posted by Mick4412
The sparky tries to balance the load over the 2 phases by wiring up
some outlets to one phase & some on the other phase.
All the waffle that we have been on about is the phase angle difference between the 2 phases....
If it's 2 phases of a 3 phase system, they are 120 degrees apart.
If it's 2 phases of a single phase system, they are 180 degrees apart.
Our house in Cairns has 3 phase power, we have 4 meters in the
meter box, one for each of the phases & one for the off-peak power.
The off-peak power is taken off one of the phases before it goes
through the meter for that phase.
If we loose a phase in our street, which can happen in certain circumstances,
about every 3rd house looses power & we loose some of the points or
lights in our house while every one else is still on.
Let me try to draw you an analogy....
Think of a water pipe with a hand pump on it & one bloke pumping.
That is how single phase AC power works.
Now think of 3 water pipes with a hand pump on each one with a bloke on each pump.
The 1st bloke starts to pump & when he is 2/3 way through his down stroke,
the 2nd bloke starts to pump & when he is 2/3 way through his down stroke,
the 3rd bloke starts to pump. By this time, the 1st bloke is 2/3 way through
his up stroke & when the 3rd bloke is 2/3 way through his down stroke,
the 1st bloke is starting again & the 2nd bloke is 2/3 way through his up stroke.
The end result is a smoother over all flow of water out of the 3 pipes
than you would get out of one pipe & pump 3 times the size.
That's how 3 phase works.
Now we get to the 2 phase from a single phase transformer.
Think of 2 pipes coming from a double barrel pump with 2 blokes
operating the one lever on the double barrel pump.
When they pull the lever one way, water comes out one pipe & then as
they pull the lever the other way, the water comes out the other pipe.
You get twice as much water than the single phase system but the flow
is not as smooth as the 3 phase system.
The load sharing the sparky does is like hooking some things up to some pipes &
other things up to the other pipes.
Hows that?
Rough with a few holes in it but it gets the point across.Cliff.
If you find a post of mine that is missing a pic that you'd like to see, let me know & I'll see if I can find a copy.
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28th October 2004, 04:48 PM #13Senior Member
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Thanks Cliff.
At the moment, the power in my existing shed works like this. I have connections to two different single phase circuits. To avoid overload, I run say,my table saw off one circuit, and the dust extractor off the other.
So, in your opinion, I can do something similar to this, with two phase, ie, have some points off one phase, and some off the other.
Have I got it right ??
thanks
mick
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28th October 2004, 06:35 PM #14Senior Member
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I'll nip in here and say - yes your right Mick and in fact from what you say, you already have 2 phases. Actually from your point of view it makes no difference whether you have 1 or 2 phases. You still can't use 3 phase gear. The only way you would find a difference is if you hang onto the active from 2 power points each on a different phase - it will hurt more because it will be 415 volts (or 480 volts if a split single phase)!!! More seriously, it does also mean that you are less likely to blow your pole fuse because you will have 2 of them. (or barge board fuse or whatever you have).
Now a comment for Cliff (and why I barged in) - Queensland and out in the sticks for sure, they appear not have heard of 3 phase meters. I didn't think anybody anywhere would still have 3 meters.
That said - I sure like your explanation of the difference between single and 3 phase power - a beauty. I am quite familiar with using water analogies for current/voltage/resistance - but had never heard that one. I must remember it.
Thanks and cheersGeoffS
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28th October 2004, 07:42 PM #15Originally Posted by GeoffS
We have our board rewired in July '99 & the local Electricity supplier had to
come out to disconnect & reconnect the meters so that their tamper seals
weren't broken & those decided to change them for new ones at the time,
they replaced all 4 of them with new ones.
The only thing I can think of is that they were trying to get rid of a pile of old
stock 'cos the new meters were all preprinted with their old name.
& Mick, what Geoff said....Cliff.
If you find a post of mine that is missing a pic that you'd like to see, let me know & I'll see if I can find a copy.