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DS_park
06-03-2015, 01:14 PM
I need 3phase 480 for my mill. 240V single phase is all I have available.
The motor is an old school 2 speed (2 sets of windings) no dual voltage. 1.2 KVA is the theoretical power use of the motor at 1.5 HP high speed. See related post http://bbs.homeshopmachinist.net/threads/66717-How-to-test-run-a-3-phase-motor


On today’s exchange rate, a UK type VDF 240 single phase to 415V 3 Phase (2HP) runs about US $800 with shipping. Not sure how much de-rating running on 415 may have.

Not counting the UK vdf option, I’m going to need step up transformer action.

Taking into account starting loads, how much transformer power (KVA – watts x 1000) rating do I need for the following?

Opt 1. 240 to 480 1P transformer to the mill with a static converter circuit installed?

Opt 2. Larger transformer 1P 240 to 480 to start and run a 3HP rpc (plus mill load)?

Opt 3. Build a 240 RPC and run the output to a 3P (or 3 separate) transformer(s) for the 480.

Both 1 and 2 could allow using a transformer as an autotransformer (ie 4KVA auto out of a 2KVA trans).

Option 3 has the merits of using 3 smaller transformers and having the 240 RPC available for other machinery in the shop.

Any other ideas?
Any one know of a 1P 480 in 3P out VFD?

DR
06-03-2015, 01:26 PM
You could put together a rotary converter to create the 240V 3 phase .

Feed that into a boost transformer to get the higher voltage 3 phase. 3 phase transformers can be expensive, but you can wire up a pair of single phase 230 to 460 transformers in an open delta configuration to boost the voltage. Google on open-delta to get the hookup wiring.

It may seem hokey to make a transformer that way, it's not. It's a widely used method. I first found out about it from a transformer company's catalog showing the method.

MaxHeadRoom
06-03-2015, 02:27 PM
What about a 240/480 1ph transformer and a 480v VFD for the spindle.
In all probability the spindle is the only thing 3ph.
You don't see many 480v VFD's and I believe this is because most manuf figure that if you have 480, it will be 3ph?
If the input is at it is with the majority of VFD's, a 3 ph rectifier, then it should run on 1ph OK, maybe derate it a HP or 2.
Max.

garyhlucas
06-03-2015, 02:40 PM
There three issues with single phase to 3 phase conversion. The first is higher current on the two input phases being used, which calls for derating. The second is higher ripple voltage on the filter caps in the input. The third is the need to disable phase failure detection to use single phase. Automation Direct VFDs in particular cannot be derated and used on single phase because you can't defeat the phase failure protection. If doing this with a transformer and inverter I would first step the voltage up to 480 single phase then use a 480 volt VFD that is derated by half. Putting a transformer between the VFD and the motor is not a good idea for lots of reasons.

hitnmiss
06-03-2015, 03:16 PM
I run a 3 phase rotary to get 240 3 phase for my CNC mill, then use a 240 to 480 three phase transformer to boost the 240 to 480 for my Feeler lathe.

Been using that combo for about 8 years now with no issues. 480 is nice, the wires are so thin!

jcurrell
06-03-2015, 04:08 PM
I run a 3 phase rotary to get 240 3 phase for my CNC mill, then use a 240 to 480 three phase transformer to boost the 240 to 480 for my Feeler lathe.

Been using that combo for about 8 years now with no issues. 480 is nice, the wires are so thin!

I am in Canada and use 575 volt, at home I have used the 240 ,3ph motor than a 3ph transformer(very bad) I got very high voltage and current on one phase. A 240 to 575 1ph transformer and 575 idler motor give more consistent volts and current.
John

lakeside53
06-03-2015, 04:25 PM
Use option 3.

I have a single to 3 phase "phase perfect" (could have used a rotary) then a 15kva 240-480 3 phase transformer. Used Transformers are dirt cheap - freight can kill. For your small needs, a 3kva transformer will be just fine. Tune your rpc well as any error is 2X on the output.

Be sure to fuse the transformer per code...

I have a 6KVA 240-480 (rated for reverse connection) here, cheap, but at 100lb or so it would cost a bundle to ship it to Michigan.

If you use a single phase transformer and a 480V vfd, take care with the derating I have a pair of high end 7.5hp ABB vfd's here (anyone want them cheap?) that are only 1.5hp on single phase - as per the manf. Don't "guess" or use "rules of thumb". The manf will tell you the correct answer.

flylo
06-03-2015, 04:25 PM
I have a new? 240/460 good size transformer. Not trying to sell on here but I bought it when I had the 20 hp lathe & never used it. PM if interested.

wierdscience
06-03-2015, 09:08 PM
I would research the possibility of using a VFD with a single phase boost xformer.A 5hp VFD can be had new for less than $200-


http://dealerselectric.com/T238.asp

Other option is have you thought about swapping motors for something 3~220vac?

Alan Douglas
06-03-2015, 09:19 PM
I use a 240:480V autotransformer to feed a 460V idler to get 3 phase for my Hardinge UM with a 3/4HP 550V motor.

macona
06-03-2015, 09:27 PM
You can't run a vfd into a transformer.

I personally would use the 240v in 415 out vfd. If it was designed to do this it does not need to be derated.

mickeyf
06-03-2015, 09:28 PM
Option 4. Can it really be that difficult to find a 240V single phase, 1.5 hp motor? Worst case you'd have to do something imaginative to mount it.

lakeside53
06-03-2015, 10:22 PM
You can't run a vfd into a transformer.

I personally would use the 240v in 415 out vfd. If it was designed to do this it does not need to be derated.

But the motor might - you are nearly 15% low on volts at full power.

PStechPaul
06-03-2015, 11:07 PM
When I was experimenting with a specially wound 3 phase 7.5 VAC 12 pole motor (originally 120 VAC single phase), I used two "wind your own" 120V to 0.4 volts/turn transformers (with 20 turns on secondaries) to a 2 HP GE/Fuji 220 VAC VFD on single phase. Worked fine up to about 240 Hz. Of course, I was dealing with only a few hundred watts.

If the VFD accepts an external DC bus link connection, you might be able to bypass the phase loss detection and run it on DC. Of course, you will need 400-800 VDC for a 440V VFD. It might be possible to use a PFC front end from a high power PFC switching supply to get about (but perhaps not quite) 400 VDC. It will more likely be about 360. But then you might be able to add a 48 VDC supply in series to get the minimum. The PFC is needed so that you can get a well-filtered DC at sufficient power without drawing too much current from the 240 VAC line.

If you don't care about power factor, you can make a "bad boy" voltage doubler from diodes and capacitors, and get the required bus voltage. Here is a 120 VAC to 320 VDC (250 VDC under load) doubler that puts out 1 kW. If you made the same thing with higher rated components and applied 240 VAC, you will get 640 VDC (500 VDC under load) at 4 kW. But PF is probably like 40% so you might draw 20 amps at 240V (4.8 kVA) to get 2 kW (3 HP) for the VFD and the motor.

http://enginuitysystems.com/pix/120Sine-320DC_Doubler.png

You could also use eight of these 48V supplies set to their maximum of 52 VDC 3.3A in series for 416 VDC and 1200W. They are $37 each and are 4" x 8" x 1.5" and weigh just 1.6 LB. I don't know if they are PFC, however. You may find some much cheaper surplus, and you can add more in series or get higher power units if needed.
http://www.parts-express.com/48-vdc-33a-150w-regulated-switching-power-supply--320-3142

Here are many more:
http://www.mpja.com/48-Volt-Power-Supply/products/544/

And a 3A 48V supply from China for $15:
http://www.ebay.com/itm/AC-110-220V-to-DC-48V-3A-150W-Volt-Transformer-Led-Strip-Switch-Power-Supply-/201278521527

Here is a 300W PFC front end circuit that provides 390 VDC, but it should be scalable to 2000W and 450 VDC output:
http://www.powerfactor.us/circuit.html

http://www.powerfactor.us/pfc-circuit.png

J Tiers
06-04-2015, 01:40 AM
You can't run a vfd into a transformer.

I personally would use the 240v in 415 out vfd. If it was designed to do this it does not need to be derated.

Well actually you can do that. I have and it works fine. It may not be so great at extremes, but it does work.

The voltage doubling VFD is, however, a better idea.

ironmonger
06-04-2015, 02:35 PM
Thought just occurred that if you found a 3 phase 240/480 motor and used it as your rotatory phase converter, could you steal the 480 off the motor windings? Sort of an rotary autotransformer...

paul

Doozer
06-04-2015, 03:58 PM
Thought just occurred that if you found a 3 phase 240/480 motor and used it as your rotatory phase converter, could you steal the 480 off the motor windings? Sort of an rotary autotransformer...

paul


I have thought of this but never tried it.
I would think you would have to connect in delta,
need to work it out on paper.

-D

MrSleepy
06-04-2015, 04:12 PM
Thought just occurred that if you found a 3 phase 240/480 motor and used it as your rotatory phase converter, could you steal the 480 off the motor windings? Sort of an rotary autotransformer...

paul

To run at 240vAc it would be wired in Delta , and Star for 480vAC .. I doubt that it has a tapped winding for both voltages.

Rob

Hopefuldave
06-04-2015, 04:25 PM
I have thought of this but never tried it.
I would think you would have to connect in delta,
need to work it out on paper.

-D

I think you'd need a 6-winding motor, connected with star connected windings at 240, the other three coils in series with the star connected windings, so you'd effectively have a 480 star motor with power in on 240v taps, out on the full 480v coils... I may be wrong though, and my vintage electrical engineering books are still packed from moving house...

J Tiers
06-04-2015, 05:10 PM
To run at 240vAc it would be wired in Delta , and Star for 480vAC .. I doubt that it has a tapped winding for both voltages.

Rob

Nope , that would change voltage by 1.73 and not 2x as required.

PStechPaul
06-04-2015, 05:11 PM
This might work on a 240/480 motor, wired for 480, with power applied to the center taps as explained above. But I think you may be limited to 1/2 (or maybe 1/4) power because the windings are rated for the current at 480V, and you are applying half voltage. However, if there is a load connected to the 480V windings, the current would split equally in the windings, and perhaps you could apply the normal current for 240 VAC. This gets complicated by the fact that the motor would be running, and drawing some power, but it may need only enough to idle if no power is drawn from the shaft.

I may try this on one of the three phase motors I have. I may even try it with a capacitor from one powered phase to the unused phase and see if it works on 240 VAC single phase. Even if it does not produce the full power rating of the motor, it might be useful. And perhaps you can use a much larger motor (say, 10 HP) to obtain up to 3 HP at 480 VAC out.

J Tiers
06-04-2015, 05:19 PM
Paul is correct because in standard RPC you have 2 wires straight thru. That current does not pass thru RPC , only the 3rd phase.

With doubler, ALL power passes thru RPC and so it will be a different ratio of power in RPC vs load. But balance should be better since impedance in all phases is more nearly equal.

dmalicky
06-04-2015, 05:40 PM
Option 4. Can it really be that difficult to find a 240V single phase, 1.5 hp motor? Worst case you'd have to do something imaginative to mount it.
+1
Ebay is a good source, typically $50-$150 selling price for one of those. My search string is
(1.5HP, "1.5 HP", "1 1/2 HP") motor -"3 phase" -"3 ph" -3ph -three -460 -DC
then try the motor categories. Look for the capacitor bulges if you want single phase.

Or craigslist is less $ -- search "electric motor" or Baldor, Leeson, Marathon, Dayton etc. As little as $35:
https://detroit.craigslist.org/mcb/mat/5040305341.html
https://detroit.craigslist.org/okl/hvo/5028703621.html

Option 5: get a 240V 3PH motor and VFD it. In this case, best to use a 2+HP motor and derate by driving at less amps.

Option 6: search for a used/broken treadmill for variable-speed at the lowest cost (sometimes free). A Baldor, for example: https://detroit.craigslist.org/okl/tls/5036674971.html

All are good solutions -- just depends on goals and budget.

mike4
06-04-2015, 06:38 PM
I have read this and many other threads with some interest , but I have a question if a rotary phase converter or other means of generating three phase from single phase is used what sort of current draw does the system have on the single phase input?

Can these systems work with serious equipment eg 12-20 hp three phase under high loads?

And the costs involved in putting the systems together from scratch , as theremay be many lurkers or others interested in using these methods for their shops.

I ask this because each time I have checked into pricing locally it was a few thousand for a system which could only run 2-3 hp .

Michael

Michael

DS_park
06-04-2015, 07:22 PM
Would a 3HP 240V RPC feeding 3 separate 1KVA reverse fed 480 to 240 transformers supply enough 480 3P to a VFD to start and run the 1.5 HP motor?

The Gorton 8D mill has a huge retro 40's looking motor. I could graft some other motor to it but it would ruin its looks.

Yup 240 would be easier. If it was a 240 motor I'd be $20 in capacitors for a built in static converter or just under $200 for a VFD but some times you got to play with the cards you draw.

DS_park
06-04-2015, 07:46 PM
This might work on a 240/480 motor, wired for 480, with power applied to the center taps as explained above. But I think you may be limited to 1/2 (or maybe 1/4) power because the windings are rated for the current at 480V, and you are applying half voltage. However, if there is a load connected to the 480V windings, the current would split equally in the windings, and perhaps you could apply the normal current for 240 VAC. This gets complicated by the fact that the motor would be running, and drawing some power, but it may need only enough to idle if no power is drawn from the shaft.

I may try this on one of the three phase motors I have. I may even try it with a capacitor from one powered phase to the unused phase and see if it works on 240 VAC single phase. Even if it does not produce the full power rating of the motor, it might be useful. And perhaps you can use a much larger motor (say, 10 HP) to obtain up to 3 HP at 480 VAC out.


Paul I agree with what you are thinking here. for a 1.5 hp mill, a 3hp rpc is needed. Feeding 240 to one set of windings instead of two in parallel, I think you would have to d-rate the motor by 1/2 as to the amount of 240 current allowed. Now the rpc grows from 3hp to 6hp. Did some google searching on this awhile back and could not find anyone who had done this. Let us know if you give it a try.

J Tiers
06-04-2015, 11:40 PM
I have read this and many other threads with some interest , but I have a question if a rotary phase converter or other means of generating three phase from single phase is used what sort of current draw does the system have on the single phase input?

Can these systems work with serious equipment eg 12-20 hp three phase under high loads?

And the costs involved in putting the systems together from scratch , as theremay be many lurkers or others interested in using these methods for their shops.

I ask this because each time I have checked into pricing locally it was a few thousand for a system which could only run 2-3 hp .

Michael

Michael

Since the RPC ONLY supplies the 3rd phase power, the input is current sufficient for 1/3 the power output, plus internal losses, and increased by the power factor. So a 12HP would need to supply only 4HP through the RPC. The rest is a direct pass-through.

With the "boost RPC" all 12 HP would pass through the RPC, and I expect that decent performance would require an RPC of 2x to 3x the load power, just to get the series impedance down.

As for cost, your "few thousand" sounds like the cost of a "Phase Perfect", a solid state device. A reasonable RPC need cost no more than a suitable sized idler motor plus an enclosure and some other components. If all bought new, well, sure, might get expensive, but a working junkyard motor is sufficient.

For the Gorton, I would NOT do BOTH an RPC AND VFD in "cascade".... Get a voltage doubler VFD and do it directly.

Or get a larger single phase transformer, and feed that to a de-rated 3HP 480V VFD.

dmalicky
06-05-2015, 12:36 AM
The Gorton 8D mill has a huge retro 40's looking motor. I could graft some other motor to it but it would ruin its looks.

If the motor is very old, I would not invest too much assuming the windings will remain good. A plus of those old motors is they are huge for their HP, so you should be able to gut it and put a modern motor inside it -- looks preserved, function much better.

macona
06-05-2015, 12:50 AM
In the rare occurrence that the VFD does have phase loss detection just jump one of the two lines to the third line in. They just sense voltage, no actually phase rotation detection goes on.

macona
06-05-2015, 12:53 AM
If the motor is very old, I would not invest too much assuming the windings will remain good. A plus of those old motors is they are huge for their HP, so you should be able to gut it and put a modern motor inside it -- looks preserved, function much better.

In the case of a Gorton 8D it has a very specific motor and mount just for that. It would be a royal pain to put something else in there, the motor is fat, but not big enough to fit another inside. Also the Gorton motors (I think made by Master) are very well balanced. I have ran a Gorton 8-1/2 off a VFD and it was quite happy.

lakeside53
06-05-2015, 01:19 AM
In the rare occurrence that the VFD does have phase loss detection just jump one of the two lines to the third line in. They just sense voltage, no actually phase rotation detection goes on.

My Abb vfd's don't bother with any particular phase detection either - but they alarm if the ripple on the DC buss gets above 14% (which would happen if you lost a phase under sufficient load). It's also how they establish derating for single phase operation.

MrSleepy
06-05-2015, 05:21 AM
As for cost, your "few thousand" sounds like the cost of a "Phase Perfect",

It will not be a "Phase Perfect" type , The UK ,EU,Japan,China, and AusNZ use a phase voltage of 220-240vAC from a single winding. 415vAC between any two phases.... So a "Phase Perfect" unit doesn't make any sense as you'd already have either 220-240vAc single or full 415vAC 3Phase ... never just two phases.
Very few 415vAC devices will only use two phases .. Transformer PSUs ... Old transformer Square wave Tigs and Oxford Oil cooled Stick sets are one of the few I can think of..but inverters have made them obsolete aswell.

Its more likely to be either a full single to 3PH inverter as Drives Direct sell , or a Transwave type RPC (with its trick 240vAC In - 3PH 415vAC out Tyco motor generator) or one with an inbuilt autotransformer (as Aboard-Epsilon has).

Rob

Doozer
06-05-2015, 07:23 AM
The OP needs 480v to run his Gorton mill motor.
Not 415v. There just happened to be a VFD for
sale in the UK like that.
-D

MrSleepy
06-05-2015, 07:30 AM
The OP needs 480v to run his Gorton mill motor.
Not 415v. There just happened to be a VFD for
sale in the UK like that.
-D

Was that a response to my reply above ...
If so ....480vAC for the OPs Gorton yes .... But JT was repling to Mike4 post ,as was I.

Rob

lakeside53
06-05-2015, 12:05 PM
Phase Perfect puts out 3 phase "better than utility" power from single phase. If you want any other voltage, a 3 phase transformer is all that required. I run one. For Mike4's $$$, that's the way I would go.

MrSleepy
06-05-2015, 12:43 PM
Phase Perfect puts out 3 phase "better than utility" power from single phase. If you want any other voltage, a 3 phase transformer is all that required. I run one. For Mike4's $$$, that's the way I would go.

A Phase Perfect generates 240vAC three phase ,not the 415vAC output Mike 4would need , and a transformer would cost quite a bit aswell. .

A transwave would probably end up a lot cheaper.

Edit .. I get the impression from the PP website (and from a previous Macona post) that the PP only generates and synchronises 1 leg of the supply to go with the other 2 phase you have from your 240vAC supply.

Is that correct ..or is it a true inverter/converter that recreates all three phases from a DC bus.

Rob

ironmonger
06-05-2015, 01:08 PM
<snip>

Edit .. I get the impression from the PP website (and from a previous Macona post) that the PP only generates and synchronises 1 leg of the supply to go with the other 2 phase you have from your 240vAC supply.Rob

Not really, the incoming 240V center tapped transformer circuit that feeds your home is single phase.

The PP stuff must generate the other two phases from the single phase it is supplied with. Don't confuse the number of wires with phases. In a three phase system in a delta circuit for instance, each leg of the delta is a common lead for two windings on the transformer...




Is that correct ..or is it a true inverter/converter that recreates all three phases from a DC bus.



Not so much recreates as synthesises. A modern VFD generates each of the phases from DC. The requirement of some VFD's that they be fed with 3 phase is more a limitation of the rectifiers or internal phase detection drop-out circuitry, not a requirement to make the 3 phase from single phase.

RE Phase Perfect... If phase perfect states their 3 phase is better than the utilities I would doubt anything else they claim. It's been said that you should never believe your own BS... true here as well.

paul

J Tiers
06-05-2015, 03:02 PM
...

RE Phase Perfect... If phase perfect states their 3 phase is better than the utilities I would doubt anything else they claim. It's been said that you should never believe your own BS... true here as well.

paul

Don't be so sure. They adjust the output to be balanced. Powerco 3 phase may or may not be balanced well, depending on how well the loads are balanced.

The PP is a good product, and there is no reason to consider them to be BS artists, unlike many of the fly-by-night suppliers of DIY RPC equipment.

MaxHeadRoom
06-05-2015, 03:13 PM
Phase Perfect puts out 3 phase "better than utility" power from single phase. If you want any other voltage, a 3 phase transformer is all that required. I run one. For Mike4's $$$, that's the way I would go.

Phase Perfect passes the 240v 1ph direct through and manufactures the 3rd ph from this, same as a RPC.
They show this in their documentation.
Max.

MrSleepy
06-05-2015, 03:19 PM
Phase Perfect passes the 240v 1ph direct through and manufactures the 3rd ph from this, same as a RPC.
They show this in their documentation.
Max.
Yes..thanks .. As I thought above ...and would be pretty much useless to Mike4 .

dmalicky
06-05-2015, 03:19 PM
In the case of a Gorton 8D it has a very specific motor and mount just for that. It would be a royal pain to put something else in there, the motor is fat, but not big enough to fit another inside. Also the Gorton motors (I think made by Master) are very well balanced. I have ran a Gorton 8-1/2 off a VFD and it was quite happy.

Yes, I see the motor via this (your!) thread http://www.practicalmachinist.com/vb/antique-machinery-history/gorton-8d-mill-174779/
Looks like everything comes out the bellhousing end. And it looks like the mounting casting (foot and waist) is a separate part from the motor casing -- is that correct?

DC/treadmill motors are small diameter.

I wouldn't assume every old motor will last with a VFD -- most do, but I would at least megger it before investing.

ironmonger
06-05-2015, 07:02 PM
Phase Perfect passes the 240v 1ph direct through and manufactures the 3rd ph from this, same as a RPC.
They show this in their documentation.
Max.

I originally confused the PP with a static converter... my bad. It's more like a VFD without the V. It appears that these devices are digital and not like a RPC at all.

So where does the other phase come from? If it passes though the original input as 1 of the phases and manufactures the third... still needs one more, so I'm gonna figure that it makes phase 2 and 3 electronically.

So if you need to buy a transformer to get 440V using the phase perfect, you might as well buy a single phase 220/240V to 440V single phase transformer and get a single in 3 out 440V VFD.

Might be a better idea to take the motor to a motor shop and have them rewind it for 220/240V three phase and buy a 240V VFD.

paul

MaxHeadRoom
06-05-2015, 08:03 PM
So where does the other phase come from? If it passes though the original input as 1 of the phases and manufactures the third... still needs one more, so I'm gonna figure that it makes phase 2 and 3 electronically.

paul

The two 1ph conductors provide two of the phase, on their own the difference is 180°, The 3rd phase is manufactured with respect to the other two to provide a perceived reference zero point of 120° between each conductor.
IOW, only one phase is 'manufactured'.
Max.

PStechPaul
06-05-2015, 10:10 PM
One way to understand the concept of phases is to picture each conductor as a point, and if you draw a line between them, you have a single vector (or single phase). Even with a center point (neutral), the vector is still only along one direction. You also have the opposite direction, of course, and sometimes the two hot conductors are referred to as "phases", but it's still technically single phase.

Once you add a third point that does not lie along the line of the single phase, you can draw two more lines between the points, and thus you have three phases, which are normally at 120 degrees. Actually, the included angles of an equilateral triangle are each 60 degrees, but the directions of the vectors are 120 degrees apart.

The PhasePerfect (as well as other static phase converters) needs to shift the phase of the original 240 VAC line by 60 degrees, and maintain the same voltage. Then, if you measure from the phase that has been generated to the other point, it will form the third leg of an equilateral triangle and thus a "perfect" three phase.

I just made a video about my recent adventures with VFDs:


https://www.youtube.com/watch?v=cW5Nk9yJXkI&amp;feature=youtu.be

MaxHeadRoom
06-05-2015, 11:49 PM
The PhasePerfect (as well as other static phase converters) needs to shift the phase of the original 240 VAC line by 60 degrees, and maintain the same voltage.

Except the PP doesn't change anything to the 1ph to produce the final 3ph 120° difference, just as a RPC passes the 240 1ph through and ends up with a the 120° difference.
They end up being 120° from each other WRT a conceptual 0° or common point.
Max.

mike4
06-06-2015, 01:42 AM
I have just read through the replies to the question that I asked and I now believe that for my application where a genuine 3 phase with reasonable current draw is required these methods of generating three phase from single phase will not be suitable .

I will be going down the diesel genset path as this will solve several problems with one blow.

I will have reliable power 24/7 , not get any shocks at the end of the billing period and also have control over the costs as our electricity is getting expensive quicker that diesel is at the moment.

Also by installing two medium sized sets I will if needed have extra capacity available by running both through a syncronising panel , like when a big machine has to be tested under load , as a couple of potential customers have .

I have also noticed that only a few have taken into consideration that here in Australia our voltages are different and methods that will work fine in the US and others regions wont be satisfactory here.

Thanks for all replies.

Michael

PStechPaul
06-06-2015, 05:33 AM
Paul I agree with what you are thinking here. for a 1.5 hp mill, a 3hp rpc is needed. Feeding 240 to one set of windings instead of two in parallel, I think you would have to d-rate the motor by 1/2 as to the amount of 240 current allowed. Now the rpc grows from 3hp to 6hp. Did some google searching on this awhile back and could not find anyone who had done this. Let us know if you give it a try.

I connected my 1.5 HP 3 phase motor for 480 VAC, but powered it on the center taps. I ran it at 10 Hz and the voltage from the VFD was 134 VAC and I got what appeared to be 180 VAC on one of the HV windings, but the meter was a bit unsteady. I think the battery was low, but it also could have been from the high voltage PWM pulses. I grabbed my cheap (free) red Harbor Freight meter which I had tried before but got an erratic display on AC, and I saw/heard a spark and the meter went dead. Found out it doesn't like AC voltage when it's in low ohms... OOPS! It did not survive, but fortunately I did. :eek:

ironmonger
06-06-2015, 11:04 AM
The two 1ph conductors provide two of the phase, on their own the difference is 180°, The 3rd phase is manufactured with respect to the other two to provide a perceived reference zero point of 120° between each conductor.
IOW, only one phase is 'manufactured'.
Max.

Nope

The 240v mains are single phase, the only thing that is 180 degrees apart are the polarities of the the two leads. The phase angle is measured by comparing the voltage/time relationship between each of the phases. Each phase is a completely independent circuit that only shares a common leg. As each phase begins it's journey from zero volts towards positive (the positive reference is arbitrary) the next phase begins 120 degrees later. If one complete cycle takes 0.0167 of a second (1 complete cycle of 60cps) 120 degrees later is .006 second. So the 1st. phase begins rising to positive (arbitrary) and .006 seconds later the 2nd. phase begins to rise on it's own circuit, and .006 seconds after that the 3rd phase begins it's rise.

120/240V 'single phase' residential or commercial branches have no phase angle relationship. The phase angle is a comparison to other voltages and since there is only one circuit there is nothing, strictly speaking, to compare it to. We call it single phase, but it is ONE phase of a three phase distribution circuit, of which we only see 1 phase in our center tapped distribution branch.


paul

J Tiers
06-06-2015, 11:13 AM
When thinking about the 120deg phase sequence, vs the "180 deg" imput, it is best to remember one thing....

With ANY PHASE, the *effective* voltage is ONLY that which appears between the two wires of that "phase", which can be called the "differential" voltage. That voltage will ALWAYS have a 180 deg difference.

There may be another voltage, a "common mode" voltage, which is added to BOTH those wires vs the system "effective neutral", but that has no effect on the "differential" voltage. (it may increase insulation requirements).

Since the new 3 phase made in an RPC or a PP does NOT have the same "effective neutral" as the single phase input, the phase angles are relative to the new neutral. There is a common mode voltage between the two different "neutrals". That accounts for the difference in phase angles "as seen from" the different neutrals.


...
I have also noticed that only a few have taken into consideration that here in Australia our voltages are different and methods that will work fine in the US and others regions wont be satisfactory here.

Thanks for all replies.

Michael

While it is true that your voltage is SLIGHTLY different, essentially in the position of the neutral vs the 240V*, that makes little practical difference. What you would end up with using an RPC is a 3 phase similar to our old "corner-grounded delta". I don't know what the effect on a Phase Perfect would be, but I believe that the PP folks can deal with that easily.

* Most folks believe the US uses 120V distribution, but in reality we use 240V, center-tapped. So most issues are merely a matter of the neutral connection.

lakeside53
06-06-2015, 11:21 AM
Mike4 : PP does put out "genuine three phase". If you want any voltages other then 220-240 3 phase (say 415), you add the appropriate transformer. You can the chose Delta or Wye output. Weren't you going to put in Gensets a year or two back?

The Phase Perfect won't care if it's down-under, in the UK or wherever. I had this discussion with PP. It just need 220-240 single phase input. The output is essentially Delta and ignores "neutral".

The PP is pretty slick. Not only does it produce excellent sine wave three phase, it presents a unity power factor and returns regenerated power (load motor spinning down) to the utility

MrSleepy
06-06-2015, 11:57 AM
While it is true that your voltage is SLIGHTLY different, essentially in the position of the neutral vs the 240V*, that makes little practical difference.

Mikes 240vAC is from a single generating winding.

Which would be near equivalent to L2 to L3 on the following ,albeit in Star/wye

http://i897.photobucket.com/albums/ac180/MrSleepy123/pp1Capture_zpsc0gsrsru.jpg

It would also leave the PP with only L1 to gnd (@240vAC) leaving L2 to groung missing.

It would be too low on the voltage rating and 1 input winding missing. Remember .. on Mike4 supply L1 to L2 gets you 415vAC.

Rob

MaxHeadRoom
06-06-2015, 12:05 PM
Nope

The 240v mains are single phase, the only thing that is 180 degrees apart are the polarities of the the two leads.

paul

Yep.

On their own the two conductors are 1 phase (180°) all you need to do is introduce a 3rd conductor that is at 120°
relative to the other two, now using each phase as a reference, the other two are at 60°, exactly as is a delta secondary, between any single pair of conductors they are 180° relative to each other, but use any phase as a reference point to the other Two, the phase angle is 120°.
The PP shows phases T1 & T2 derived directly from the 240 1ph input and the 3rd manufactured phase as T3.
As in a delta secondary there is no actual neutral point but the 120° indicates an implied neutral zero point from which to draw the vector.

Max.

MrSleepy
06-06-2015, 12:23 PM
Mike4 : You can the chose Delta or Wye output.

According to the installation manual , a PP can only drive a delta load. Star via transformer.


http://i897.photobucket.com/albums/ac180/MrSleepy123/pp2Capture_zps8sodyyql.jpg
They emboldened the text ,not me.

Rob

Doozer
06-06-2015, 03:14 PM
Yep.

......The PP shows phases T1 & T2 derived directly from the 240 1ph input and the 3rd manufactured phase as T3.....

Max.

You have still got it not totally correct.
The Phase Perfect (or an RPC for that matter)
manufactures 2 additional phases. Not 1 additional phase.

Local Phase 1 is on T1 and T2
Made Phase 2 is on T1 and T3
Made Phase 3 is on T2 and T3

Get it?

-D

MrSleepy
06-06-2015, 03:37 PM
You have still got it not totally correct.


I think your wrong Doozer..

The installation manual shows both legs as a single phase needed to power it , and that those two legs L1 and L2 are passed straight through ,as in an RPC. The PP then synthesizes the third leg T3.

http://i897.photobucket.com/albums/ac180/MrSleepy123/pp3Capture_zpswz5rynvm.jpg

and
http://i897.photobucket.com/albums/ac180/MrSleepy123/PPCapture_zps0shk0gv2.jpg

taken from http://www.phaseperfect.com/files/Op%20&%20Install%20Phase%20Perfect.pdf

Rob

MaxHeadRoom
06-06-2015, 03:41 PM
You have still got it not totally correct.
The Phase Perfect (or an RPC for that matter)
manufactures 2 additional phases. Not 1 additional phase.

Local Phase 1 is on T1 and T2
Made Phase 2 is on T1 and T3
Made Phase 3 is on T2 and T3

Get it?

-D

I DO GET their schematic in their technical manual that distinctly shows the 240v 1 ph directly fed to the two output phases to T1 & T2 via two contactor contacts.
The T3 is shown coming from a electronic circuit manufacturing this phase from the other two.
Max.

Doozer
06-06-2015, 03:57 PM
Max-
In my post I quoted you as saying that the PP manufactures the third phase.
"...and the 3rd manufactured phase as T3.....
The PP makes 2 phases, not 1.
It has an additional wire, T3, which carries 120deg worth of each of the 2 made phases.

-D

The Artful Bodger
06-06-2015, 03:59 PM
Single phase is only a 'phase' of the distribution pole transformer. Viewed from the consumer's end the concept of 'phase' becomes less relevant as there is nothing to measure the phase angle against!

MrSleepy
06-06-2015, 04:05 PM
Max-
In my post I quoted you as saying that the PP manufactures the third phase.
"...and the 3rd manufactured phase as T3.....
The PP makes 2 phases, not 1.
It has an additional wire, T3, which carries 120deg worth of each of the 2 made phases.

-D

Are you not convinced by data provided by the manufacturer of Phase Perfect ,that they pass through 2 legs and create 1.

If Phase Perfect cannot convince you ... what can Max do ?..

ironmonger
06-06-2015, 04:13 PM
I think you should just buy the Genset.




http://bbs.homeshopmachinist.net/images/misc/quote_icon.png Originally Posted by Doozer http://bbs.homeshopmachinist.net/images/buttons/viewpost-right.png (http://bbs.homeshopmachinist.net/showthread.php?p=986751#post986751)
You have still got it not totally correct.
The Phase Perfect (or an RPC for that matter)
manufactures 2 additional phases. Not 1 additional phase.

Local Phase 1 is on T1 and T2
Made Phase 2 is on T1 and T3
Made Phase 3 is on T2 and T3

Get it?
-D


Doozer has it right.

paul

Doozer
06-06-2015, 04:17 PM
I read the posted Phase Perfect documentation.
THEIR nomenclature is wrong.
It is confusing you and others.
The PP manufactured leg is 120 deg from T1 and 120 deg from T2.
It makes 1 leg which is 2 phases.
-D

The Artful Bodger
06-06-2015, 04:49 PM
It is confusing you and others.
I am easily confused.


The PP manufactured leg is 120 deg from T1 and 120 deg from T2.
It makes 1 leg which is 2 phases.
-D

Well yes, every leg has a phase angle relationship with the other two legs, so why dont we call this a 6 phase system then?

MaxHeadRoom
06-06-2015, 04:55 PM
It is confusing you and others.
-D

Not confusing me.
Many cannot see or understand how you can obtain true 3 phase from a 1ph 240 pair without a need to 'Modify' the 1ph pair!!!
Max.

MrSleepy
06-06-2015, 05:30 PM
This is all semantics...

The PP needs a 208vAC single phase input arranged as two phase to ground Legs... or ... a 208vAC single phase input derived from 2 legs of a 3 leg grounded wye source.

So it can be argued that it takes in a single phase and creates 2 ,with respect to the single phase supply input (doozers arg) ... or ... it takes in two "phase to ground" legs and creates a third . (PP Arg).

So we are essentially arguing the same outcome , but referenced differently. Phase V Phase to ground.


So Re: Mike4s ability to use a PP.

Mike4 has the almost universal 3 leg grounded wye source. It is 415v 3 phase but a 415vAC single phase (as in L1 to L2) with a 240vAC L1 phase to ground.

Mikes 240vAC voltage is not center tapped , but phase to ground. So would be too high for the PPs input aswell as missing a phase to ground (L2).

If Mike4 introduces the missing phase to ground L2 , then the voltage between L1 and L2 is 415vAC single phase and would definately cook the phase perfect.

Rob

lakeside53
06-06-2015, 05:45 PM
PP doesn't care less about any neutral or grounded conductor. It just needs a single phase (200 volt class) supply. You just feed it 240, grounded neutral on one leg or not. It's output is Delta - also not not referencing any neutral. If you want a neutral in the PP three phase system, feed it though an appropriate transformer and derive a new neutral point (delta -> Wye) which you can (and are likely required to) ground.

J Tiers
06-06-2015, 05:56 PM
Mikes 240vAC is from a single generating winding.

Which would be near equivalent to L2 to L3 on the following ,albeit in Star/wye


It would also leave the PP with only L1 to gnd (@240vAC) leaving L2 to groung missing.

It would be too low on the voltage rating and 1 input winding missing. Remember .. on Mike4 supply L1 to L2 gets you 415vAC.

Rob

It makes NO DIFFERENCE.

We have 240 line to line. He has 240 line to neutral. The PP does not care about neutral. There is NO "missing" L2, because the PP is not looking vs ground, only vs the other wire, whatever it is.

Therefore it will receive a perfectly acceptable input, which will NOT BE too low, it will be exactly the same as in the US. PP says so, and it makes sense.

Remember, I said it would come out equivalent to "corner grounded" 240V, and that is exactly what happens. With a PP or with an RPC.

The conceptual problem here is a total misunderstanding of the way the US power is set up.

The reason it drives a delta load is because it has no internal reference to neutral whatsoever. US neutral is 120V from either input. Mike4's neutral is one of the wires coming in.

In either case, to supply a wye load, the existing neutrals are of no use, so the transformer is needed. It is not a "deficiency" in the PP, but a fact of the external wiring.

lakeside53
06-06-2015, 05:58 PM
According to the installation manual , a PP can only drive a delta load. Star via transformer.


http://i897.photobucket.com/albums/ac180/MrSleepy123/pp2Capture_zps8sodyyql.jpg
They emboldened the text ,not me.

Rob

Not sure where the confusion is. You might want to read what I wrote again. What I said to Mike4 - you choose the appropriate transformer for Y or delta output (off the transformer). He's stepping up voltage so need to choose a transformer and type. I do exactly this with a PP driving a transformer for 480 ( in my case delta-> delta), and for 240 I take it directly out of the PP.

Their reference to 208V is simply a diagnostic indicator of what you'd read to physical ground- you certainly don't reference it for deriving power. As T1 and T2 are passed though you can however reference T1 and T2 to INCOMMING neutral and get 120, via the appropriate circuit breakers etc. But you do not have to or need to.

Am I the only guy on this site that actually owns Phase Perfect? lol. The are high hundreds to thousands of such installations around here - used where three phase is either not available or simply uneconomic (in many case it is cheaper to use single phase and PP than to have 3 phase utility charges).

MrSleepy
06-06-2015, 06:20 PM
The PP does not care about neutral.

If I am confused .. its because page 10 of the installation manual makes reference to a grounded center tapped source on two of three examples of how to wire the PP for non wye sources.

Rob

lakeside53
06-06-2015, 06:24 PM
But it's not required in any way - just how most/many single phase supplies are configured so we get both 240 and 120. The PP only needs 200-240, and does not need a neutral.

I could feed it from a 240v non-center tapped transformer winding if I liked.