Tool Talk

I'm surprised 25% of housing would have 3phase. I know of no-one .... friends or extended family that have it. Infact if you look at the street most probably don't have all three phases running past there house.

Old industrial equipment that is to obselete for business is very cheap these days. As no-one ca run it if its 3phase ... and most hobbiest probably can't fit it in (if they can run it).

My brother rents a big industrial shed... I think it costs about $20k a year to rent and even it doesn't have 3phase!

seeya
Shane L.
 
That's interesting. We have three-phase but the previous owners (a) had an electric kiln for pottery (THAT must have used some power) and a bore for the garden, it being Perth. I know no-one else with three-phase power in the suburbs.

We export power but the price paid is pitiful. Satisfying though.
 
Rob, my place was wired years ago with a 5 kW or thereabouts load AC compressor, now long defunct. Pulling a bunch of wire from the board cost no more than the small conductor cost.. The fuses and simple switches cost peanuts. The original work apart from AC is on a single phase sub board with breakers. There was an extension later using two of the phases direct from the AC fuses. Cost of the extension electrical was bugger all.

I spent some money instead having to move the point of attachment and re-cable through the building to the board. Funnily, Ausgrid has done it again since for free. They also wanted to replace the multiple meters with a new one, but there is no mobile reception, so it has faded away.

The others in the street with 3 ph either have AC units or workshops, now with new meters. At least it keeps the phases balanced.
 
There is 3 phase about a km away from my house. It would cost heaps to have it brought to my workshop. I have so-called "2 phase", which is actually 480 volt centre-tap single phase. I have two single phase to 3 phase converters, neither of which I have commissioned yet. One takes a 240 v input; the other takes a 440 v input but comes with a stepdown transformer from 480 v. The industrial sparky mate who gave me the 240 v one said their output is noisy and emits a lot of interference, so he gave me a few metres of shielded 3 phase cable for its output.

I have just picked up an old Repco 471 wheel balancer with all the adapter plates for weird wheels such as our froggy wheels. It's 3 phase, so I might have to hook up a converter.

Roger
 
It shows the variations in rural services. One of my family on a rural line has 3 phases and neutral aerial conductors connected and run from the road pole into the meter section, but only a single phase is used. The others are ready if needed, presumably.
 
Roger Wilkinson said:
There is 3 phase about a km away from my house. It would cost heaps to have it brought to my workshop. I have so-called "2 phase", which is actually 480 volt centre-tap single phase. I have two single phase to 3 phase converters, neither of which I have commissioned yet. One takes a 240 v input; the other takes a 440 v input but comes with a stepdown transformer from 480 v. The industrial sparky mate who gave me the 240 v one said their output is noisy and emits a lot of interference, so he gave me a few metres of shielded 3 phase cable for its output.

I have just picked up an old Repco 471 wheel balancer with all the adapter plates for weird wheels such as our froggy wheels. It's 3 phase, so I might have to hook up a converter.

Roger
Click to expand...

The EMI that is emitted from these devices is a down side to them, using braided or SWA cable does help a lot to reduce such issues.

If you are a long way from your neighbours Roger you will e the only one that suffers from the problem.
 
Roger Wilkinson said:
There is 3 phase about a km away from my house. It would cost heaps to have it brought to my workshop. I have so-called "2 phase", which is actually 480 volt centre-tap single phase.
Click to expand...

I beg to differ, two phase is simply two of the three phases run into the premises.

Of course there is 415 volts between the two phases, as their is between any of two phases of a three phase supply.

There are No transformers nor any other equipment. 415V Three phase supply always has 415v between each phase and 240 v between each phase and neutral.

This is due the trigonometrical relationship between the phases, IE each phase is 120 degrees lagging from the next sequential phase


three phase.JPG

This also explains why three phase circuits are permitted to use the same neutral cable cross sectional area as the phases

EDIT: Here is some more on trig relationships, albeit fo US voltages. The formulae are still valid for the Au system.

https://pacificpower.com/2017/07/understanding-three-phase-voltage/
Click to expand...
 
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seasink said:
Connection across two phases happens where it can for 415 v, but isolated areas may get two phase 180 degrees separated for 480v.
See eg http://www.phasechanger.com.au/power-optimisation-article.pdf
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It's not strictly two phase, because a transformer is used and the phase difference and voltage is as a result of the transformer.

It must be a rural system. It doesn't happen in the city, Supply companies would not want the extra cost and complexity of a transformer, especially in view of the fact three phase supply is already a available.

I may owe Roger an apology. :rolleyes:


Phase changers can be a thing from hell. Essentially they are a specially wound motor used as a rotary transformer. They are full of harmonic products and can vary in frequency if not matched to their load.

OK for for non critical devices like motors. Personally I'd think twice before using on critical equipment with inbuilt electronics . :wink2:
 
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It is like this: 2 ph.png

Motors are wired to suit.

Also found is High Voltage Single Wire Earth Return, where transformers are used to supply a single or two phase service, with return to earth.
 
G'day,

I had a two-wire 415V supply put on at the parents when I was a teen to supply a stick welder - an offshoot cash sale jobbie from a guy that made up commercial spot welders, lovely welder, tad heavy though.... also runs on 240V and still in use.... :)

Anyway, the sparkie that helped me with the install told the elec supply crowd that it was in preparation for a new stove as it was much easier to get the OK from them for the connection. Dunno about all the techno, but, he mumbled something about the old meters not reading the true consumption due to power factor problems, unbalanced loads and slow startup when coupled with the rather large welder....

He divided the house load up between the two phases, made Dad a bit nervous as you could have an extension lean from one room into another and end up with 415V available in one place....

cheers,
Bob
 
Concrete grinding

G'day,

I need to level up a small section of ancient concrete floor removing from zero up to say 3-4mm over about four sq feet - twin fridge alcove.

Looking past a hammer and chisel and a sore elbow, I have available an Aldi "kanga hammer", not very controllable, similarly, an air chisel. I note though that there are repurposed angle grinders, two obvious contenders....
https://www.bunnings.com.au/full-boar-1400w-125mm-concrete-grinder_p0122287
https://www.totaltools.com.au/126895-detroit-125mm-1400w-d-handle-concrete-grinder-detcog1400
with the cheaper Detroit weighing in at a good bit heavier than the other.

I 'spose I could also get attachments for the grinders already here, but at the prices for the ready made article you would have to wonder why.... :)

OK, anyone here had experience of these things ?

thanks,
Bob
 
For that small an area Just Kanga-jack it into bits and re-lay the concrete, the old stuff is probably of low quality anyway, do it once and do it right. If you do decide on the grinding down - the right tool and good breathing mask is essential make sure your good lady is also protected from the dust.

Just my thoughts, laying new concrete is easy, satisfying and doable..

Ken
 
bob said:
G'day,

I need to level up a small section of ancient concrete floor removing from zero up to say 3-4mm over about four sq feet - twin fridge alcove.

Looking past a hammer and chisel and a sore elbow, I have available an Aldi "kanga hammer", not very controllable, similarly, an air chisel. I note though that there are repurposed angle grinders, two obvious contenders....
https://www.bunnings.com.au/full-boar-1400w-125mm-concrete-grinder_p0122287
https://www.totaltools.com.au/126895-detroit-125mm-1400w-d-handle-concrete-grinder-detcog1400
with the cheaper Detroit weighing in at a good bit heavier than the other.

I 'spose I could also get attachments for the grinders already here, but at the prices for the ready made article you would have to wonder why.... :)

OK, anyone here had experience of these things ?

thanks,
Bob
Click to expand...

Hi Bob, both those machines are the business and will do a fabulous job and will save you from silicosis in the process. I suspect they don't include a diamond grinding head in that price which might take the grin off your face.
 
I know how "it'done"

I alluded to that in post # 2291.

Regardless it needs an additional transformer and devices which are happy powered from a 2 phase, 240 volt , supply with 180 degree phase rotation angle, which is a pretty strange device, in the city anyway.:eek:
 
I have my own transformer, on the road about 500m from my house. There is a 3 phase 66kV line there but only two phases in the 22kV line. The transformer takes these two for its primary winding and from its secondary comes three tappings. My house has a single phase meter. The two "phases" go to a point in the workshop that provides 480V single phase (3 wire including earth). Everything else on the farm is connected to the "phase" that is not connected to the house. The farm has a 3 phase digital meter. Before that meter was installed it had an analog meter labelled "2 phase 3 wire".

I have several single phase electric motors that will accept either 240 or 480 V input. Also an arc welder that has primary windings for 480, 415 or 240 V. I have it set for 480V.

This was common in rural areas where 3 phase supply was often not available. It is often used in SWER supply areas as a way to get more current out of a single supply wire. We had the same system in the Yarra Valley when I was growing up, despite being less than 20 miles from the centre of Melbourne.

In my younger days I tried to understand how it worked. I knew about 3 phases 120 degrees apart, and the 415 delta voltage, and could not understand how 480V could be obtained. I asked every sparky I met and none could explain it. Finally an electrical engineer mate said it would be single phase centre tapped and it all made sense.

Roger
 
Like the diagram if the centre tap is earthed. Ordinary domestic circuits are on one of the phases. They try to balance the loads on each phase to reduce the residual current in the neutral.
 
G'day,

bob said:
Concrete grinding

G'day,

I need to level up a small section of ancient concrete floor removing from zero up to say 3-4mm over about four sq feet - twin fridge alcove.

Looking past a hammer and chisel and a sore elbow, I have available an Aldi "kanga hammer", not very controllable, similarly, an air chisel. I note though that there are repurposed angle grinders, two obvious contenders....
https://www.bunnings.com.au/full-boar-1400w-125mm-concrete-grinder_p0122287
https://www.totaltools.com.au/126895-detroit-125mm-1400w-d-handle-concrete-grinder-detcog1400
with the cheaper Detroit weighing in at a good bit heavier than the other.

I 'spose I could also get attachments for the grinders already here, but at the prices for the ready made article you would have to wonder why.... :)

OK, anyone here had experience of these things ?

thanks,
Bob
Click to expand...

well, got the Detroit, nope it's not a couple of bricks, the box says 2.8kg - advertised at 5kg..... Aaah, yes, tiny writing on the box "disc not included" :)

Anyway, yes it works, sort of. Turns out the diamond cups, in it's own brand, come out well below the hairy curtain. The nett effect of this little oversight is that copious amounts of removed concrete is spread everywhere except where it should be - into the vacuum cleaner canister, damn nuisance.

It was making such a mess that I didn't do the whole job, although I don't doubt that it was up to the task - just as long as you don't want to play with it inside..... :mad:

cheers,
Bob
 
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