Thread: 3-phase Electicity

In this country most electricity is reticulated as three phase.
If you are at the end of a run all 3 phases may not come past your house.

check out the power poles.
4 wires side by side is typical 3 phase, 3 phases & neutral.

single phase is any one phase & neutral ie 240 volt normal electricity.

If you look carefully at the wires you will see that diferent properties take their electricity fron different phases.

3 phase is all three phases.
there is still 240 volt between any phase & neutral.
however there is 415volts between any two phases.

There is no implications for any single phase devices in the installation because they will be run off one phase only.

Three phase motors may be cheaper because they are much simpler.

All single phase motors incorpirate some form of jigery pokery to simulate some for of multi phase situation otherwise the motor would not statt or rotate Sounds bizare!!!

Three phase & single phase have no greater or lesser propensity to generate interfreerence, however because 3 phase gear is considered industrial it may not be as well surpressed as smaller domestic gear.

I can testify to the sale cost of 3 phase gear. At auctions I have been to 3 phase gear goes cheaper than single phase because more of the buyers can't use it.

I recon that If you are in a situation where you will always have 3 phase available it is a good choice.

If you may not always have 3 phase I'd stay with single phase gear but that mostly limits you to 3HP motors or smaller thinking of a 15Amp circuit.

Hi All

I'm a refrig mechanic by trade, work for a sparky and a woodworker in my spare time so I thought I would chip in on the three phase debate as I tend to deal with it a bit.

If you have three phase onto your house then getting one three phase outlet in the shed shouldnt break the bank. If you want a fancier setup with a sub board and multiple outlets then be prepared to shell out a bit

If you don't have three phase then it can be a bit more difficult especially if you have underground power or if you live in perth even with aerial power (Western power will not do aerial three phase changeovers anymore, must be undergrounded)

Where I work we normally charge between $450 - $1000 inc. GST for three phase mains changeovers for our part and the local western power charge is about $300 for a meter changeover and $700 for them to underground the supply to your boundary.

If you are building a new place then get it done when you first sort out your building contract as it does not cost (note cost) a great deal more for the cable and three phase main switch and associated bits. But if you are dealing with a builder then they always tend to gouge you for it.

A real big killer with three phase stuff is the price of things like power points and plug tops. Trade price on a 10 Amp three phase four pin power point is about $90 cost and a 10 Amp three phase plug top is about $45 or $50. Which is a big difference between a normal power point!! When you need a few of those it starts to add up pretty quickly. If you get your machines hardwired with just an isolating switch it will drop the cost a bit but then you have less flexibility if you need to move stuff around.

But is does have its benefits, my scheppach over and under planer has a three phase 2.2kW motor (3hp) wired in delta (440V) it only draws 4.7 amps per phase and you hardly notice when it starts up.

Three phase is also very easy to reverse if you ever need to just swap two of the phase around and hey presto the motor goes the other way. Which explains Bastards law of three phase motors " the motor will always go in the opposite direction to the way it is supposed to go the first time!!!!"

I hope this helps a bit

Darryn

As soundman said earlier, it is usually pretty easy to see if 3 phase aerial runs past your house - just look for 4 lines between the poles.

I'm trying to determine the situation at the house I am about to move to soon. Does anyone know how to find out easily and quickly if 3 phase runs from the pole to your house and panel? Is it just a matter of looking at the aerial cable between the pole and your house or do you need to look more closely at the panel?

I have pictures of my house's aerial connection, old panel and street posts that I can email to you if you are interested in helping me...:confused:

Hi ndru,

It should be simply a matter of looking at how many power cables run into your house. Houses with single phase will have just two cables (one phase and neutral). Fairly obviously, two cables won't be sufficient for three phase, so if you're seeing more cables, you're in luck.

Of course, if you have underground cables, it may be more tricky, and you'll probably have to examine the panel. Sounds like your cables are all aerial, though, so it should be easy.

Incidentally, driving along the road, you can usually tell which houses have air conditioning ... they're the ones with more power cables going in!

Originally posted by ndru
As soundman said earlier, it is usually pretty easy to see if 3 phase aerial runs past your house - just look for 4 lines between the poles.

I'm trying to determine the situation at the house I am about to move to soon. Does anyone know how to find out easily and quickly if 3 phase runs from the pole to your house and panel? Is it just a matter of looking at the aerial cable between the pole and your house or do you need to look more closely at the panel?

:

The easiest way is to look in your meter box, the things to look at are
A your electricity meter, normally they are marked 1 or 3 phase somewhere unless its one of those flash new electronic ones.

B The meter fuses, black things which are sometimes wire sealed which are usually near the meter. 1 of those = 1 phase 3=3 phase

C The main switch If its old and surface mounted it will probably be narrow (not much wider than the switch lever) if considerably wider than the switch lever most likely to be 3 phase.

If its a modern board which has DIN rail fittings (modular system) a single phase main switch is one pole space wide and a 3 phase is three poles wide

HTH

Darryn

Now to take this thread to a different phase(excuse me) and now that April Fools day has been and gone and to put a different perspective on the topic.

There was an Company in the Blue Mountains that either imported or produced a converter taking the current from an ordinary single phase GP (general purpose ) outlet and producing a 3 phase outlet.
These converters came in a range dependent on the capacity of the machinery you intended for it.
They had a starting price of around $1500 and were portable but hefty.
Being naturally a dubious suspicious bugger I rang the guy up and asked him to send me all the guff on this converter.
I then had it checked out with an Electrical Engineer who at first appeared sceptical when I rang and asked him to have a look at the fact sheets and diagrams.
He concluded that it was ok given the technology employed.
I was investigating this after seeing it advertised in the Australian Woodworker in the mid 90's and when I was considering chucking out the Orange stuff and upgrading.
I still have the paperwork around ..I just cannot lay my hands on it at the moment.
I naturally didn't go ahead after discussions with the war office that perhaps the money would be better employed on a universal single phase machine which consequently happened.

Cheers

There are a few american sites which detail how to run three phase machines off single phase. And a few years ago there was an article in Silicon chip magazine about it (I think their site has a a search function)

There are two main ways of doing it, one is to use large motor start and run capacitors to only power up two of the windings and the other is to get a separate three phase motor running via single phase (using the above method) and then once the motor is running you will actually pick up the second and third phase from the motor windings.
Search for "rotary phase converter" on google

The rotary type converter is best as it can handle dynamic loads better than just using capacitor conversion

The kicker is you will need a spare three phase motor which is as big or bigger preferably than the biggest motor you are trying to run!

Of course there is a bit more involved than just that but it is a bit of a start

Darryn

TV interference unfortunately can be a fact of life especially on low end VHF channels.
This can come about from certain pieces of equipment that run on three phase and the emissions run along the pwer lines.
Another problem is that some of the private power companies tooik to replacing the timber cross bar off the tops of the poles, the ones that carry the insulators and power (single or three phase) they replaced them with metal, as they will not need to be replaced periodically due to rot, ants etc.
The problem now is that a number of 50hz wires running over a metal bar equals a low frequency radiator, read antenna and to hell with anyone trying to watch channel 1 to 6 within 100 metres.
The only cure for TV addicts is to go digital or hope the ABC has a UHF option as filtering is almost useless.

I have two points to follow on.

Three phase conversion is in most cases a real waste of time because the cost of any effective contrivance will probably be greater than a replacement motor and less convoenient. In addition no convertor will be any better than 75% efficient in practise & the total power consumption of most three phase equipment in question will be greater than can be convieniently obtained from a single phase circuit.
For example if a 5hp 3 phase motor were to be run on a convertor it would probably draw in excess of 30 amps single phase.


Concerning the interfeerance matter in this case I feel it is a red herring and has nothing to do with the matters under discussion.
In my once more vigorous role as a TV antenna contractor and my current role aa a sound system contractor I have had to contend with all sorts of interfeerance and the causes are many and varied and the source of much speculation and superstision and almost devoid of serious technical consideration for the most part.

My spectrum analyser attached to a low band log periodic with a 9db gain detects 65 to 68 dbu within 100 metres of the offending poles.

My TV suffers accordingly despite the 70 75 dbu generated by the transmitters on Mt Dandenong.

ABC is unwatchable and untreatable, hence the conversion to a digital set top unit which operates on channel 12.

Not superstition or otherwise, its real and out there, and the power companies don't give a stuff.

Originally posted by soundman
I have two points to follow on.

Three phase conversion is in most cases a real waste of time because the cost of any effective contrivance will probably be greater than a replacement motor and less convoenient. In addition no convertor will be any better than 75% efficient in practise & the total power consumption of most three phase equipment in question will be greater than can be convieniently obtained from a single phase circuit.
For example if a 5hp 3 phase motor were to be run on a convertor it would probably draw in excess of 30 amps single phase.

Fair enough sound man I was only trying to give a bit more info on how it could be done if necessary, I've never done it myself as my house has 3phase already

Single phase is not without its problems either as inrush current needs to be dealt with too. I don't know about other states but in WA there is a 45A maximum inrush current allowed on single phase equipment connected to the grid.

Darryn

Transwave Converters is what they were called and I have found the paperwork for this stuff which was sent to me by their W.A. agent in Ron Mack Machinery Sales in Perth.

Rather than having to scan everything in I have done a search and come up with a web-site.

http://www.arharris.co.nz/Datasheets/transwave.htm

Cheers

This is another link to converting single to 3 phase

PJ & PJ TAYLOR Pty Ltd
40 Spencer Street, JANDAKOT WA 6164
Tel: (08) 9417 1769 Fax: (08) 9332 4416
Developers and makers of the POLYPHAZ Single to Three Phase converter for achieving 3-phase power in your workshop

I've got a Vicmarc VL 300 Electronic lathe. This has an inverter which converts the single phase input to three phase. Doesn't interfere with the radio, the telly, or the next door neighbours dog!
I don't really know what I'm talking about here and am quoting a sparky friend who was amazed at the lack of interference on any of the stations on my shed radio.