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Don't know what to do...Need 3 phase power somehow..

RC99

RC99

Diamond
Joined
Mar 26, 2005
Location
near Rockhampton, Queensland, Australia
My workshop recently saw a new addition with a 10hp lathe...All my other gear is single phase and it has limited me greatly as to what I could buy...

I need power to run this new lathe and have a few options but am unsure of the best way to go..

Firstly I should get the power upgraded to 415V 3 phase..This would cost somewhere between 10 to 15 thousand dollars even though it is only 400m away and all that has to happen it for the power company to run one wire and replace the current transformer..Also I would have to upgrade all the switch board in the shed..

Option two is to upgrade to 480V split phase, unsure of costs there...

Option three and the cheapest but nosiest and most labour intensive is a 20KvA generator, I already have a engine suitable to run it...

Option four is a 7.5Kw phase converter on the 240V mains...I have priced two locally made ones and they run around $4500 but they use electronics for the control and I am concerned about life expectancy, and product support ten years down the track..

Option five is to get a 5 or 7.5hp single phase motor and use it, but it again limits what I can do down the track with newer machinery..

Anyone think of any other options???

Here are some links to the two locally made phase converters...

http://www.polyphaz.com/

http://www.phasechanger.com/index.php
 
Get a runable three phase motor about 1 1/2 times as big as the biggest motor you intend to start and build a rotary phase convertor - info abounds on doing such in this section.

This assumes your 240 mains have suitable amps to do such.

I start this 15 HP on 240v single phase with only start caps (1000mfd). It could just as easily have run caps and be a rotary phase converter. 100 amp breaker but only 50 amp slow blow fuses in disconnect. #6 AWG wiring makes for no light dimming.

http://www.practicalmachinist.com/vb/showthread.php?t=158528

John Oder
 
.RC. said:
But isn't all US 240V single phase actually dual phase???? And your 3 phase is 220V unlike our 415 Volt...
Click to expand...

All single phase, just with center tap so 2 x 120V to ground.

As for voltage, so what? We also have 480V 3 phase as a common industrial voltage. So you use higher rated components. The motor is no problem, if 415 is common, motors will be available.

The rotary converter is the cheapest reasonable solution. A motor, plus some parts. A VFD is nice, but for that application it will likely be significantly more expensive.
 
.RC. said:
But isn't all US 240V single phase actually dual phase???? And your 3 phase is 220V unlike our 415 Volt...
Click to expand...

You are correct on both counts. It all depends on how you think about such things. You Australians call what the US has as "two phase" to differentiate between the US and Australian systems.

AS far as 3 phase voltage goes, you can get almost any voltage you want depending on what you tell the power company to install and how deep your pockets are. Most (many?) 3 phase motors for the US are dual voltage capable. 230 and 460.

As far as a lathe solution goes, you have all your options listed.
 
What i see in Australian voltage supply is this....single phase is rated 240/480, but in there three phase motor voltage ratings they are rated 240vac up to 3hp, and 415vac from 5hp and larger.
In order to design a RPC from 5Hp and larger, you would first need to use a single phase transformer to setup from 240vac to 415vac. Then you can design a RPC panel rated at 415vac with a idler motor rated at 415vac.
 
Some folks do the rotary conversion first at 240 volts,
and use a three phase transformer to step up to the
higher voltage.

Both work.

It's basically a question of what surplus components
can be obtained, cheapest - that will dictate the best
path to take.

Jim
 
Jim
That setup will work fine in the U.S. but in Australia you will not find a three phase motor rated at 240vac from 5Hp and up, as they are all rated at 415vac. So in this situation I would think you would need to increase the single phase voltage to 415vac in order to match the voltage of the idler motor at 415vac....If I am wrong about this, please tell me...As we are designing RPC panel for a Australian vendor, and any input that you can add would be great.
 
Let's get the voltages and so forth straight here.......

415 delta is 240V "Y". So are we talking about "Y" or delta setups here?

A motor wired "Y" and used on 415 delta is therefore a "240V capable" motor. If re-wired delta, it could be used for an idler in the 240V side of a 240 to 415 setup.
 
RC, you stated in your post that the power company "would only have to run one wire" to give you three phase. Does this mean that you, like me, have a true two phase power set-up, with a two phase meter and panel?

If so, I have been told that it is possible to make a RPC using both of these 240v phases, and with the resultant manufactured third leg you would have 415v three phase. This isn't an issue for me yet as all of my three phase load can be run 240v delta except for one motor. (I am currently seeking a three phase step-up transformer for that 1 kva load)

Such an RPC would be pretty rare I think, but there is enough data and expertise on this site to choose properly sized capacitors if you are going to roll your own.

$4500 for an RPC seems like a pretty sporting quote for something you can make for a few hundred with eBay parts.
 
JST does bring up a good point here, 415 delta motor can be internally reconnected to a wye connection ( 415 x .58 = 240vac ). This way you would need to use a three phase transformer on the output side of the RPC from 240vac to 415vac
 
That system in the link ends up with a fairly conventional "corner-grounded" 3 phase system.

"Corner grounded" is well known in the US, the building I work in is wired with 'corner grounded" 240V 3 phase.

In any case, depending on transformer availability, you have the choice of a single-phase 240V to 415V transformer first, with 415 idler and motor, or a re-wired-to-240V idler, and a 3 phase transformer to get 415.
 
It seems that in Oz you use "standard" Uk type mains, the options I see are firstly open up the motor and see if in the terminal box there are any strappings, if the 415 3 phase goes to three terminals with another three terminals shorted together, then the motor winding are actually 230V and it is strapped for star connection. if there are just three terminals then the windings are rated at 415V. If there are three pairs of strapped terminals then the windings are rated at 415V with an option for use on 680v (!)
So depending on the motor the option could be:-
230V -> 230V 3 phase convertor(cheapest)
230V - transformer to 415V, 415 convertor -> 415 3 phase*
230V ->230V 3 phase convertor - 3 phase transformer -> 415 3 phase
* this is what I use with a static convertor
One thing to bear in mind depending on how often this lath is used is the running cost of the total set up i.e. the overall efficiency and power factor (do you get billed fro real power or VA?). Another factor worth ponderinng over is the size of the 230V wiring, 10hp = 7kW, allow 5 X inrush = 37Kw =~150A@230V. My 3hp(2.2kw) motor has blown a 30A fuse in the past( 6.9kW).
Frank
 
Greg Quenneville said:
RC, you stated in your post that the power company "would only have to run one wire" to give you three phase. Does this mean that you, like me, have a true two phase power set-up, with a two phase meter and panel?
Click to expand...

No, we only have true single phase, yes two phases go into the main transformer on the pole but we only get one phase out...There must be a reason why they do it this way..
 
Too bad. My house has this bizarre two phase* set-up, apparently becaue they wanted to put the air conditioner load on a seperate phase from the rest of the domestic load. Putz builder has a three phase connection at the street, but only ran two conductors down the (40 metre) trench. As you know the cost would have been minimal for three phase then, not so much now.

*yes, even have a two phase meter. 2 X 240 + PE + Neutral

greg
 
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