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Andrew Johnston20/07/2021 19:54:59
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Super yachts have power converters that take shore power from anywhere in the world and generate clean 3-phase for distribution around the yacht. Here's an example:

Shore Power Converter

I don't own a super yacht, so don't know how much they cost.

Andrew

Bob Worsley20/07/2021 20:03:53
103 forum posts

This is an interesting thread, lots of opportunity for the magic blue smoke to leave!

What is a split phase 480V AC supply? It seems to be from posts that it is two 240V supplies but independant of each other so you do actually get 480V live to live? Where on earth does it come from? This arrangement of two supplies that can be used live to live seems to be an American thing, 110V to 220V.

Talking about 30kW output, have you costed a 30kW transformer? Might be a long way towards the 3ph install cost.

Don't forget that the only way to convert single to three, or multiple, phase is by using energy storage devices, capacitance, inductance or inertia, and inertia is the cheapest.

Seems to me that buying a diesel generator is much the simplest solution, something about 60kW is about £4k secondhand. Again, be aware of the synchronous reactance which is what makes a 10kW generator power only a 5kW load. For the plasma cutter you don't need AC, since it works internally from a DC bus. Similarly for 400V 3ph VFDs, they all seem to use an internal DC bus and the AC doesn't do anything.

A 100A 400V 3ph supply is about 24kW, seem to be beyond that?

Robert Laurenson20/07/2021 20:04:25
48 forum posts
Posted by Robert Atkinson 2 on 20/07/2021 18:58:45:
Posted by John Haine on 20/07/2021 16:09:52:

The operating principle is described in this patent. It's quite clever and not as Robert describes. There's a published IEEE paper also in 2019 22nd International Conference on Electrical Machines and Systems (ICEMS) (This may be difficult to access.)

Leaving aside the question of the patent, reproducing this at home looks very difficult! Not only is there the question of hairy power electronics, but the real-time control software looks quite tricky.

I agree with others who suggest separate VFDs per motor, which would turn out probably cheaper than either a 3 phase supply or one of these hairy beasts, or one of the more primitive static or rotary converters. I think you have one or two machines that are particularly problematic, the press brake and welder? Don't let the peak power requirement for these impose unrealistic costs and complexity on the rest of the solution.

Edited By John Haine on 20/07/2021 16:10:16

Edited By John Haine on 20/07/2021 16:14:45

Hi John,

Thanks for the link. It's certainly not as originally described and has some key components not shown in the installation manual. That said the Patent i terrible and does not reveal anything about how it actually works. Presumably it is using PWM and the output capcitors (not shown in manual circuit) are doing a lot of the work. Thi is supported by that that they have to be reguarly checked / replaced.
It's whats not in the patent and specification that would bother me. No output voltage spec other than about the same as the input. No output power factor range. No minimum load. No step load change response. Some of the patent claims are a bit broad e.g. basically any circuit with a phase controlled input bridge and polarised storage capacitor would breach it. Lots of prior art to get around that one. The patent does not mention PWM or if they don't use PWM how they generate the waveforms. All in they must have some pretty advanced math to generate the required waveform for zero to unity PF over 0 to 118kVA. I've recetly been working with some custom <50kVA converters and the supplers of those have struggled to meet specification even with full 3 phase bridges and limited load power factor.

It's also does not appear to be suitable for UK use. Standard is 60Hz and there are no claims for any safety or EMC approvals. They have the ELT mark on parts of documents but only their variable speed drives are listed and then to very limited tests

https://ramuk.intertekconnect.com//WebClients/ITS/DLP/products.nsf/vwSearch?SearchView&Query=FIELD%20ListHead%20Contains%20phase%20perfect%20or%20FIELD%20CatCode%20Contains%20phase%20perfect%20or%20FIELD%20Title%20Contains%20phase%20perfect%20or%20FIELD%20ProductInformation%20Contains%20phase%20perfect%20or%20FIELD%20ProductInfo%20Contains%20phase%20perfect&SearchOrder=1&SearchMax=1000&SearchWV=FALSE&SearchThesaurus=FALSE&SearchFuzzy=FALSE

If any of the machines to be powered have a neutral connection (5 wires) then a delta/star transformer will be required.

Hi Robert,

Speaking with Phase Perfect just now, and they can supply it as 50hz, so no issue there.

And i will have to run it through a transformer anyway due to the 480v, i need it down at 440 ish to run my equipment.

To be honest i do think now that its the only way to go.

Robert Laurenson20/07/2021 20:11:07
48 forum posts
Posted by Bob Worsley on 20/07/2021 20:03:53:

This is an interesting thread, lots of opportunity for the magic blue smoke to leave!

What is a split phase 480V AC supply? It seems to be from posts that it is two 240V supplies but independant of each other so you do actually get 480V live to live? Where on earth does it come from? This arrangement of two supplies that can be used live to live seems to be an American thing, 110V to 220V.

Talking about 30kW output, have you costed a 30kW transformer? Might be a long way towards the 3ph install cost.

Don't forget that the only way to convert single to three, or multiple, phase is by using energy storage devices, capacitance, inductance or inertia, and inertia is the cheapest.

Seems to me that buying a diesel generator is much the simplest solution, something about 60kW is about £4k secondhand. Again, be aware of the synchronous reactance which is what makes a 10kW generator power only a 5kW load. For the plasma cutter you don't need AC, since it works internally from a DC bus. Similarly for 400V 3ph VFDs, they all seem to use an internal DC bus and the AC doesn't do anything.

A 100A 400V 3ph supply is about 24kW, seem to be beyond that?

Hi Bob,

The 480v supply is as you say, the same as the american sinle phase 3 wire system. It comes from a centre tapped single phase transformer on a pole where only two phases are running on the poles rather than 3, quite common in rural areas in the UK.

The 40kva transformer ive had a quote for 3200 delivered, so with the phase perfect thats about 11k all in. Still 30k off the SSE costs. So looks like a good price for what im getting all in. Not decided yet but certainly leaning towards it.

John Haine20/07/2021 20:21:13
4188 forum posts
242 photos
Posted by Andrew Johnston on 20/07/2021 19:54:59:

Super yachts have power converters that take shore power from anywhere in the world and generate clean 3-phase for distribution around the yacht. Here's an example:

Shore Power Converter

I don't own a super yacht, so don't know how much they cost.

Andrew

Anything for yachts is automatically more expensive. As the saying goes, if you have to ask the price, you can't afford it! And: sailing can best be described as standing under a cold showevr tearing up fifty pound notes...

Andrew Johnston20/07/2021 20:29:33
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6283 forum posts
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Posted by Bob Worsley on 20/07/2021 20:03:53:

...........A 100A 400V 3ph supply is about 24kW.........

A 100A 3-phase supply is 100A per phase, so 3x240x100=72kW.

Andrew

Robert Atkinson 220/07/2021 21:11:15
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Posted by Robert Laurenson on 20/07/2021 20:04:25:

Hi Robert,

Speaking with Phase Perfect just now, and they can supply it as 50hz, so no issue there.

And i will have to run it through a transformer anyway due to the 480v, i need it down at 440 ish to run my equipment.

To be honest i do think now that its the only way to go.

 

Make sure your electrician and supply company are happy with it before you spend the money. It has NO UK / EU approvals at all. That means it may not be legal to use. I'm not sure what the current requirements for fixed industrial electrical equipment are. If it is a non-industrial installation it has to be approved equipment.

Robert G8RPI.

Edited By Robert Atkinson 2 on 20/07/2021 21:11:50

Robert Laurenson20/07/2021 21:13:48
48 forum posts
Posted by Robert Atkinson 2 on 20/07/2021 21:11:15:
Posted by Robert Laurenson on 20/07/2021 20:04:25:

Hi Robert,

Speaking with Phase Perfect just now, and they can supply it as 50hz, so no issue there.

And i will have to run it through a transformer anyway due to the 480v, i need it down at 440 ish to run my equipment.

To be honest i do think now that its the only way to go.

Make sure your electrician and supply company are happy with it before you spend the money. It has NO UK / EU approvals at all. That means it may not be legal to use. I'm not sure what the current requirements for fixed industrial electrical equipment are. If it is a non-industrial installation it has to be approved equipment.

Robert G8RPI.

Edited By Robert Atkinson 2 on 20/07/2021 21:11:50

Hi again,

It is (if i buy it) being installed in an industrial unit, so should be ok from that side of things.

Just have to wait and see, ill mull it over a while yet.

Thanks

Robert

Stuart Smith 520/07/2021 22:10:13
231 forum posts
27 photos

Robert

As someone who worked for over 40 years as an electrical power engineer for my local DNO ( or electricity board as it used to be), I would suggest you check with SSE to see what load and motor starting currents you can take from your existing supply. As per my post in your previous thread on buying a lathe:

”Robert

Although the fuse carriers on your main DNO fuses may be labelled as 100A , you would be advised to check what current you can actually take from the network. I used to work at Electricity North West and the maximum supply capacity there was specified as 20kVA for a single phase supply ( ie 80A). The other issue may be that the rating of the pole mounted transformer may be a limiting factor. Also there are limits on voltage fluctuations caused by motor starting currents or welders (see ENA ER P28).

Stuart”

Regarding the ‘Phase Perfect’ - it seems to be anything but perfect.

It is clear from the diagram in this document

https://www.phasetechnologies.com/downloads/New_Phase_Perfect_Specifications.pdf 

that the two existing phases are used as they are and the third phase is generated electronically. So the two phases will be 180 degrees apart and presumably the extra phase will be 90 degrees from them. The phase to phase voltages will be as per the supply (ie somewhere in the 450 to 500 volt range depending on the loads on the network etc)

Stuart

 

Edited By Stuart Smith 5 on 20/07/2021 22:20:09

Edited By Stuart Smith 5 on 20/07/2021 22:20:59

Robert Laurenson20/07/2021 22:25:32
48 forum posts
Posted by Stuart Smith 5 on 20/07/2021 22:10:13:

Robert

As someone who worked as an electrical power engineer for my local DNO ( or electricity board as it used to be), I would suggest you check with SSE to see what load and motor starting currents you can take from your existing supply. As per my post in your previous thread on buying a lathe:

”Robert

Although the fuse carriers on your main DNO fuses may be labelled as 100A , you would be advised to check what current you can actually take from the network. I used to work at Electricity North West and the maximum supply capacity there was specified as 20kVA for a single phase supply ( ie 80A). The other issue may be that the rating of the pole mounted transformer may be a limiting factor. Also there are limits on voltage fluctuations caused by motor starting currents or welders (see ENA ER P28).

Stuart”

Regarding the ‘Phase Perfect’ - it seems to be anything but perfect.

It is clear from this diagram that the two existing phases are used as they are and the third phase is generated electronically. So the two phases will be 180 degrees apart and presumably the extra phase will be 90 degrees from them. The phase to phase voltages will be as per the supply (ie somewhere in the 450 to 500 volt range depending on the loads on the network etc)

Stuart

Hi Stuart,

Thanks for the reply,

Ive spoken to them and they said max 48kva, 75kva transformer on the pole.

They also said the cable they installed to my premesis is big enough they could double it to 100kva split phase. (with a transformer upgrade)

The equipment im looking at, the only big motor is the press brake, but its a soft start servo motor so that shouldnt be an issue either as far as start surge goes.

The phase perfect, that bit you said about 180 degrees is exactly what i thought. Looking at forums, it seems to not be correct. Found a video online showing an oscilloscope monitoring one under several load conditions and the phases being perfectly balanced.

The 480v output seems to be the only issue and the lack of Neutral. So i have got a couple of quotes for a delta to star isolation transformer to step down the voltage and give me a neutral. By the sounds of it it will work.

Again regarding the 180 degrees apart bit i saw an analogy which someone wrote under the video of the PP sine wave monitoring.

They said something along the lines of this.

If you put 3 stakes in the ground as an equilateral triangle, if you stand between two posts they are 180 apart and the other is at 90, if you stand next to a single post the otber two are at 60, and in the middle they are all at 120. Said he was an electrical engineer and had a PP system running all kinds a stuff from a cnc lathe to other things. Not sure if what he said is right, but it makes sense in simple terms. If i were to use a rotary converter i would still be putting the two 240 legs in and making the 3rd, so its just a digitally balanced version of the same is it not?

Stuart Smith 520/07/2021 22:54:26
231 forum posts
27 photos

Robert

Yes, I was thinking of the voltages and phases measured to the existing neutral. I can see that for a delta connected supply, it would work as you say, so your idea of a delta/ star connected transformer would give a neutral and correct the voltages.

Regarding the supply capacity, as well as the kVA rating there is also the effect of any sudden changes in load such as welders and motors. Your DNO may have already told you what maximum welding and motor starting currents you can have. There is an Energy Networks Association (ENA) document Engineering Recomendation P28 which DNOs use to calculate these figures ( though they may have their own policies based on this).

**LINK**

Stuart

Edited By Stuart Smith 5 on 20/07/2021 22:57:59

Edited By Stuart Smith 5 on 20/07/2021 22:59:02

Robert Laurenson21/07/2021 06:38:20
48 forum posts
Posted by Stuart Smith 5 on 20/07/2021 22:54:26:

Robert

Yes, I was thinking of the voltages and phases measured to the existing neutral. I can see that for a delta connected supply, it would work as you say, so your idea of a delta/ star connected transformer would give a neutral and correct the voltages.

Regarding the supply capacity, as well as the kVA rating there is also the effect of any sudden changes in load such as welders and motors. Your DNO may have already told you what maximum welding and motor starting currents you can have. There is an Energy Networks Association (ENA) document Engineering Recomendation P28 which DNOs use to calculate these figures ( though they may have their own policies based on this).

**LINK**

Stuart

Edited By Stuart Smith 5 on 20/07/2021 22:57:59

Edited By Stuart Smith 5 on 20/07/2021 22:59:02

Stuart,

Yes the DNO said the supply was capable of direct on line starting of a 15kw load, so more than enough for what i will be doing. My welders are all new inverter type machines so no sudden surges and biggest is 300a so nothing big. Plasma the same, so i think i will be ok in that regard.

thanks

Stuart Smith 521/07/2021 09:00:43
231 forum posts
27 photos

Robert

Looks like you have it all covered.

Be interesting to see how the overall costs compare to having supply upgraded to 3 phase.

Stuart

Andrew Johnston21/07/2021 09:36:18
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6283 forum posts
677 photos

Posted by Robert Laurenson on 20/07/2021 22:25:32:

If you put 3 stakes in the ground as an equilateral triangle, if you stand between two posts they are 180 apart and the other is at 90, if you stand next to a single post the otber two are at 60, and in the middle they are all at 120. Said he was an electrical engineer and had a PP system running all kinds a stuff from a cnc lathe to other things.

All it means is that the reference point is being moved, basic geometry. The angles change but also the magnitudes, so the system will not be balanced. Not really comparing like to like. Of course perpendicular phases may well work, depending upon the application.

I worked for a company where one of the electrical engineers insisted that 4000 series logic had three states, not two. He then proceded to demonstrate that soldering on a circuit that is live at 600V with a grounded tip is not a good idea. Consequently I'm a bit cynical when people state that they're X or Y, the implication being that they know what they're doing. disgust

Andrew

John Haine21/07/2021 14:08:55
4188 forum posts
242 photos

OK, reading the paper and thinking about this a bit more the operating principle is explained in this phasor diagram.

3phase.jpg

Here the + and -240 volt phasors are the two legs of the centre tapped mains supply (all voltages are given in RMS though strictly they should be peak). The + and - terminals of the supply become two of the phase voltages, the phase-phase voltage being 480V.

What the unit mainly does is via some clever power switching electronics generate a third voltage in quadrature with both and a voltage level of 415V which feeds the third phase terminal. This becomes the third phase.

If you now look at the phase-phase voltages and angles, they are all 480V rms and mutually at 60*, that is a true balanced 3-phase supply. Note that there is an implied "neutral" which is not at the same potential as the mains input "neutral", so you would need to be careful using the supply to machines that needed earthing for safety. This could be fixed by using a 3-phase isolating transformer with a star secondary where the star point is used as a neutral (and could be connected to mains neutral and PME).

It ought to be obvious that the phase and amplitude balance depends on controlling the generation of the 415V auxiliary signal to be at the right level and exact quadrature, but for a DSP this is trivial at 50/60Hz. There is no reason why the system should not generate 3 phase as accurate as a conventional VFD, with the benefit that only one power output stage is needed. 

The actual product, if as described in the paper, has some switched capacitor trickery to save components in the power amplifier but I think essentially follows this operating principle. I think it's rather neat!

Edited By John Haine on 21/07/2021 14:10:26

John Haine21/07/2021 15:47:24
4188 forum posts
242 photos

One might ask of course, why doesn't a conventional VFD work this way? The answer is that the system only works at the mains frequency so motor speed can't be varied.

SillyOldDuffer21/07/2021 16:35:49
Moderator
7574 forum posts
1681 photos

I'm struggling to understand, but might be nearly there! My version of John's diagram:

digitalphase.jpg

If the rightmost point of the triangle were at 480V (twice 240V), the phase angles would be two at 63.5° and one 53.1°, which is much better than an idler motor or static converter could do. The volts are balanced, but the phases are up to 6.9° out. However, if the unit reduces the output (rightmost) to 415V, as John's diagram, the phases are all balanced, at the cost of a slight voltage imbalance, also better than an idler motor or static converter.

Presumably the electronics could adjust the generated phase anywhere between 415 and 480V to improve either phase balance, or voltage, but not both. For example 447.8V gives two 480V phases at 61.8° and one 447.8V phase at 56.4°

Is that right? Doesn't seem to be covered in my manual:

Dave

John Haine21/07/2021 16:58:22
4188 forum posts
242 photos

I don't think it is! To get the value of the quadrature voltage, suppose it is V while the phase-phase voltage is 480V. Then you have a right-angled triangle with hypotenuse 480, one right-angle leg 240, while the other is V, and the angle at the upper vertex is 60*. Then the value of V must be sqrt(3) x 240 = 415.69. Voltages and phases are all correct. If the voltage was 480 as in your first assumption, then the second two phase-phase voltages would be greater than 480.

Stuart Smith 521/07/2021 18:28:30
231 forum posts
27 photos

I agree with John.

Did a bit more thinking about it and I think if the phase to phase voltage of the existing split phase supply is 480v, the generated voltage is 416 with respect to the existing neutral.

The only thing I would say is that if Robert goes down this route, the star point of his proposed delta/star transformer (ie the neutral for his 3 phase output) should be earthed separately and not connected to the existing supply neutral.

Stuart

Robert Atkinson 221/07/2021 20:13:24
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1091 forum posts
20 photos

Robert,

I checked on the latest guidance regading approvals. If you buy this equipment from the USA YOU wuld become responsible for getting it approved to UK (UKCA mark) or for a limied time EU (CE Mark) standards. Specfically it would have to comply with the RoHS (hazardous substances), Low Voltage Directive (electrical safety) and EMC directive (interference). The cost of this would be unrealistic for a single installation. This may seem just red tape. It is possible that no one will ever question it, but like speeding without a licence, even if you are no caught, it is still illegal, dangerous and may leave you uninsured. Lowest level imact your power supplier tells you that tyou have to disconnect it. Next is it causes interference, you get fined and have to stop using it. I'll leave out the interference causing a plane crash, it's highly unlikey but emissions form power line have contributed to a commercial aircraft crash in the past. Worst, it catches fire, causes something else to catch fire or electrocutes someone. Your insurance does not payout and you get prosecuted.
Not likey people will say, but this is a big unit connected to a (preumably long) power line. It could cause conducted and / or radiated emissions and harmonics that affect others. The producton of harmonics can overheat teh supply transformer or affect other users on the same supply. If your converter blows up another consumers equipment the bill could be very large.

Robert G8RPI.

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