Using a US manufactured digital phase conveter in the UK

[English Frank]

My home workshop has three woodworking machines, all fitted with dual voltage 3 Phase motors, currently configured for 415V 50Hz. My workshop power supply is 230V single phase 50A. I have been using a static converter to provide the three phase but I would now like to upgrade to a digital phase converter manufactured by Phase Technologies LLS in the US. Web address and specific model phaseperfect.com/files/pt330specs.htm
The makers are helpful but I am not qualified to understand their replies.

I understand that static and rotary converters are far from perfect and would like to move to and advance technique that seems to offer a perfect solution providing the change of frequency and input voltage can be accommodated.

Thanks in advance

 

[jim hardy]

reading their datasheet leaves me with two questions.

1. OOps my mistake - They say it's useable 50 or 60 hz so that one's answered

2. They say on http://phaseperfect.com/files/pt330specs.pdf page 2 that its 3 phase output power is same voltage as its single phase input .
"Voltage Equal to single-phase input voltage – 187-260 volts"

and your motors are 415 volts? Your input is 230? Sounds to me like you'll have a mismatch.

 

[English Frank]

Thank you for your reply.
My motors are dual voltage and can be changed from 415V to 230V 3 phase.

 

[jim hardy]

My motors are dual voltage and can be changed from 415V to 230V 3 phase.

that sounds like the answer.

Check the "KVA code" on your motors, it gives you their starting current. It's usually several times running current.
Make sure the electronic gizmo has capacity to start your motors.

http://www.engineeringtoolbox.com/locked-rotor-code-d_917.html
http://www.joliettech.com/nema_codes-ac_motors.htm
http://www.gillettegenerators.com/sizing/sizing03.html

Good luck !

old jim

 

[English Frank]

Hello Jim
Surely not that old!

I will check the motor kVa - I note that this converter accommodates a 4 second overload of 150A.

One final question (I hope) Can you open the following link (phaseperfect.com/files/op_inst_pt.pdf) and look at Fig. 6; my limited electrical knowledge seems to detect the need for an additional transformer between my power supply and the L1 & L2 inputs of the converter! If I am correct, Phase Perfect will be able to supply one but to minimise shipping costs I would prefer to source one in the UK - are you able to advise details of a suitable transformer.
Many thanks
Frank

 

[English Frank]

Hi Jim
Just found this on another site and it seems to clear the fog on my understanding of the US power system but not how Phase Perfect create 3 Phase.
Thanks
Frank
Wiki:

A split phase electricity distribution system is a 3-wire single-phase distribution system, commonly used in North America for single-family residential and light commercial (up to about 100 kVA) applications. It is the AC equivalent of the original Edison 3-wire direct current system. Its primary advantage is that it saves conductor material over a single ended single phase system while only requiring single phase on the supply side of the distribution transformer. Since there are two live conductors in the system, it is sometimes incorrectly referred to as "two phase". To avoid confusion with split-phase motor start applications, it is appropriate to call this power distribution system a 3-wire, single-phase, mid-point neutral system

 

[bison_bloke]

I'm an electrician, and as far as I can tell, these seem to be a good unit (though I have never used one).

The biggest question is how much power you need to run your machines. You need to work this out so that you don't end up choosing a unit that's too small, and also so that you don't overload your supply.

A 3 phase machine rated at 10 Amps will draw a lot more than that through the line side of your converter (from memory you multiply your current by √3, but that could be wrong).

If you've got machines with dual voltage connections, they will have dual voltage windings or tappings inside, you won't need a voltage converter.

Motor startup shouldn't be a problem with the high inrush currents it can provide; although you may need to install a 'd' curve circuit breaker on the supply to your shed if it starts tripping on startup.

 

[sophiecentaur]

Hello Jim
Surely not that old!


Frank

Oh yes. Jim and I were pals of Michael Faraday.

 

[English Frank]

YES! and I went to school with A. Einstein but he grabbed all of the brains!

On this link xxx.phaseperfect.com/techinfo.htm "Operation and Installation Manual - PT Series" diagram 6 shows a diagrammatic of the US electricity grid supplying 120V x two to L1 & L2 of the converter - I presume that I could achieve the same inputs with a 230V transformer with a centre tapped output & 2 x 120V.
If I am correct; next question, can you suggest the specifics including the required kVa of a transformer that will do this job.

 

[jim hardy]

Oh yes. Jim and I were pals of Michael Faraday.

Seems like that was just yesterday - when we were young...


Maybe Sophie can help us out here too. I don't know how British power is delivered.

First , the figure you reference shows a third wire connected to "ground" at both source and at the unit.
http://phaseperfect.com/files/op_inst_pt.pdf fig 6
That might represent either an earthing connection, or a neutral connection.
(The difference between an earthing connection and a neutral connection is the neutral normally carries current; while the earthing one does not- it's there only for safety during faults.)
I suspect it is an earthing connection. Many 240 volt appliances in US do not use a neutral.
Page 3 shows two line connections and one ground connection, notably absent is one labelled 'neutral'.

Whether this is a current carrying connection should be verified by a phonecall to Phaseperfect, or their UK representative..
http://www.phaseperfect.com/

Sophie will know how British power is earthed. US power is earthed as in fig6 top sketch.
I'm going to assume having done a quick search, that in England one side of your incoming 240 is earthed and called "neutral".
Sophie - please help !

I am going out on a limb here, but i think your Phaseperfect gizmo needs only the two incoming power leads and a safety earthing conductor. That conductor must be large enough to trip the branch breaker in case of fault so make it the same size as your power wires..

If i am wrong you will have to create a center-tapped 230 volt supply.
The 100% surefire way is to use a transformer rated same as the phase converter, 230 to 230 volts ~10kva with centertapped secondary and Earth that centertap..
That seems awfully cumbersome and i will be surprised if it's necessary. This seems a sophisticated machine that's aimed at international market. Surely they are too smart for that.




This should be verified by a phonecall to phaseperfect, or their UK representative..
http://www.phaseperfect.com/

A question well phrased is half answered

"I am in UK and have 240volts 50 hz.
It's not centertapped for neutral as in US.
Instead one side of incoming 240 volt line is called 'neutral' and is earthed back at service transformer..
Can i connect your equipment to this system?

If the answer is "yes",
then kindly observe:
What is 'Neutral' to me will be either L1 or L2 to you.
Which one of your terminals, L1 or L2, should receive my 'neutral' (low) wire?
The other will receive 240.

I assume i should connect my earthing conductor to your "ground" terminal for safety, or as you call it 'bonding'..
And i understand it must be sized same as L1 and L2 in order to assure it will trip branch breaker in a fault.

I look forward to your clarification of these details.

Shoot 'em an email with that pasted in and follow up with phone call?

If any of it is unclear to you please advise. I'm a Yank, you know, and we are not known for precision and clarity in our use of English.

old jim

ps speaking of British hobbyists - i recently read (again) "Trustee from the Toolroom". Might you know of it ?
It was one of the formative events of my youth.

 

[jim hardy]

post- ps if it turns out a transformer is neeeded i'll help pick one.

Also did you note their caution about output being delta only ?

The three-phase output is delta configured. While the phase-to-phase voltages are equal, the phase-to-ground
voltages are not equal. Phase-to-ground voltage for both T1 and T2 should be approximately 120V. Phase-toground
for T3 should be approximately 208V. For three-phase loads that are designed for delta connection, the
load derives its voltage phase-to-phase, so the phase-to-ground voltage should not affect the operation of the
equipment. If the connected load has a neutral connection and requires wye configured power, the output
of the phase converter must be passed through a delta-to-wye isolation transformer before connection to
the load.

in other words, it's not equal voltage from each output line T1 T2 T3 to neutral.
In your case, one output terminal will be at neutral. See block diagram page 6 of PDF, manual page 1 (right after iv).

 

[English Frank]

Good morning Jim
First let me clarify the UK domestic supply system. At street level the supply utilities distribute 3 phase, 415V ac power, a neutral, the protective Earth is provided either by ground spikes or via the utilities armoured cable sheath. Each phase to neutral provides 230V.
Each dwelling will have a 1 phase 230V supply (one of the three phases), a neutral plus the protective earth. The utilities balance the 3 Phase load by using a different phase to neighbouring properties.
Three phase power is only supplied as standard to factories and other large users.
Back to the Perfect Phase device. My latest question to Phase Technologies is :-
"Dear Steve
I have been continuing to study your documentation and believe that I am close to understanding how the US provides electrical services to small consumers and how this relates to the supply side requirements of the PT 330. On the diagram (6) it shows a transformer providing the two hot lines at 120 V Can you specify the kVa of a centre taped transformer that would transform the UK’s 230V into the two 120V lines.
Regards
Frank

His reply
" Frank
You do not need a transformer. You can supply 230V to one leg and 0V to the other.

The previous email :-

Good morning Steve

Sorry but I need further clarification before ordering the PT330. Please appreciate that I am a clock maker/cabinet maker so my electrical knowledge is limited.

Please let me explain. My supply is 230Vac 50Hz and 50A. This consists of L1 (hot) (230V), Neutral & protective Earth.

All of my motors are dual voltage without neutral; the manual states 4.0 HP (3.0kW) 220-254/380-440V.

A/ The UK supply is 50Hz, does the Hz difference rule out the use of your convertor in England.
B/ What would need to be done electrically to connect the UK single phase 230V to the input of the PT330?

Do hope that you can find time to conclusively determine the suitability of using the PT330 in England.

Kind regards
Frank

A. We can operate at 50Hz
B. All phase converter outputs are Delta. Input at 230V will give you 230V output. You would need a transformer on the output if you required 415V.
phaseperfect.com/files/op_inst_pt.pdf Here is the install manual.

What is the significance of the output being delta only?
Frank

 

[sophiecentaur]

Seems like that was just yesterday - when we were young...


Maybe Sophie can help us out here too. I don't know how British power is delivered.

There has been quite a lot of info since you wrote this, Jim, but I have some thoughts. There have been many threads on this forum involving confusion between the two systems (US / UK).
It's interesting how the two systems developed and why. I am sure it's to do with population density and original choice of domestic voltage. In the US they couldn't afford to distribute from a central point at LV so they use HV distribution and individual transformers on poles- designed to a price and hence the unbalanced primary. In the UK, there is mostly underground distribution from a local 'sub-station' and the Earth is provided largely by the sheath on the company cable to the house. LV cables are seldom more than a couple of hundred metres and allowing the common neutral to float will reduce losses when the demand on the phases becomes unbalanced. The difference in supply voltages between US and UK further justified the different choices of the two systems. The UK doesn't use the split phase and domestic dual voltage that the US does. I believe the 240V option must have been a retro-fit in the US, which was introduced as domestic loads got bigger.

 

[jim hardy]

Thanks fellows ! UK distribution now makes sense.


Frank i tend to be always a paragraph behind any conversation. I have grown accustomed to it though.

Okay - so they've already confirmed they will accept 240 between L1 and L2 with one side 'grounded'( i prefer term 'earthed') . That's very sensible of them.

So the converter should be happy connected to your supply, 240 single phase one side earthed.

What is the significance of the output being delta only?

Draw yourself an equilateral triangle with sides 2.4 inches long.

Label the three vertices T1 T2 and T3 .
That's a scale drawing of your three phase voltage, 100 volts per inch.


Now observe from installation manual's block diagram on page 1 (page 4 of PDF) that:
T1 will be connected by the contactor to L2; and
T2 will be connected to L1; and
T3 will be created by the electronics .

T1 and T2 are 240 volts apart, that's defined by input L1 and L2.
T3 is placed by the electronics equidistant from T1 and T2. The electronics places it 240 volts equidistant.
Notice there's no neutral or ground. The gizmo doesn't really need them, it would work in an aircraftcraft or on the moon.

So now add to your triangle an Earth connection at , say L2.
Nothing really changes so far as the converter's electronics are concerned.
Your motors will see T1 "earthed", but they won't care so long as their insulation is sound.

Now back to your triangle
Now add arrowheads so that the triangle looks like it's rotating CCW.
Now our graphical representation of the 240 three phase voltage has become a "Phasor diagram".
All that means is the arrows now indicate phase angles of your three voltages by their direction on the paper.

Now locate the center of your triangle/phasor diagream, the point in middle equidistant from all 3 vertices.
IF there were a neutral that's where it would be.
The Phaseperfect folks did not bring out a neutral, in fact may not even have fabricated one internally, so there just isn't one.
That's the only significance . If you need a neutral you have to make it yourself.

........

Now if you wish draw another phasor diagram with sides 4.15 inches long.
That's utility power. They hand to you one phase and neutral as you have already described.
By grade school geometry you can show that distance from any vertex to neutral will be 4.15/√3 = 2.4 inches.

So your Phaseperfect converter will hand you a three phase triangle, 240 volts per side with one vertex earthed instead of its neutral earthed.


That should be just fine for motors. On low voltage connection they'll be wound delta anyway.

If you have a high inertia load like a planer you might start it first.

I apologize for the length of this post. I think in pictures and words come with great difficulty. But i try to paint a picture in listener's mind. If I've meandered offtrack please call me out on it.

Sophie - you are better with words than i, if you improve on this i'll be honored.
Probably there's a ten word answer just it didnt come to me.

old jim

 

[jim hardy]

I believe the 240V option must have been a retro-fit in the US, which was introduced as domestic loads got bigger.

interesting question.

Wiki suggests it's a vestige of the early Edison DC systems, which you fellows may not have had to endure.
I don't remember them but worked with some electricians who did.

Originally, the service voltage was about 90 volts direct current (VDC) which was Edison's plan. Tesla proposed that the electrical grid be alternating current (AC) and competed with Edison for the first generating plant to be built in the State of New York at Niagara Falls. Edison proposed a DC system and Tesla an AC system. History tells us that Tesla won the competition, and because of that the industrial revolution was quickly accelerated. Had Edison won we would probably still be in the dark ages because of the inefficiency of transmitting DC current over long distances. While Edison was promoting the electrical light bulb around the country, almost every town required its own generating station because DC would lose so much in the transmission that it became unusable after only a couple of miles.

Tesla also had invented the poly phase alternating current generators that provided for the ability to generate the voltages necessary for long distance transmission. Tesla kept the voltage about the same as what Edison started but raised it to the 110 volts alternating current (VAC) because of the higher related voltages of 220 VAC and 440 VAC, which were integral to the more efficient poly phase generators.

Read more: http://wiki.answers.com/Q/Why_was_1...e_US_and_not_some_other_voltage#ixzz1wM1X8q3f

Split-phase systems require less copper for the same voltage drop, final utilization voltage, and power transmitted than single phase systems. (Voltage drop tends to be the dominant design consideration in the sizing of long power distribution cable runs.) Just how much depends on the situation. However, the extra conductor may require more insulation material and more complex processing, reducing the cost saving for lower power runs.
Fig. 4

In the United States, the practice originated with the DC distribution system developed by Thomas Edison. By dividing a lighting load into two equal groups of lamps connected in series, the total supply voltage can be doubled and the size of conductors reduced substantially.
Fig. 5

If the load were guaranteed to be balanced, then the neutral conductor would not carry any current and the system would be equivalent to a single ended system of twice the voltage with the live cables taking half the current. This would not need a neutral conductor at all, but would be wildly impractical for varying loads; just connecting the groups in series would result in excessive voltage and brightness variation as lamps are switched on and off.

By connecting the two lamp groups to a neutral, intermediate in potential between the two live legs, any imbalance of the load will be supplied by a current in the neutral, giving substantially constant voltage across both groups. The total current carried in all three wires (including the neutral) will always be twice the supply current of the most heavily loaded half.

For short wiring runs limited by conductor ampacity, this allows three half-sized conductors to be substituted for two full-sized ones, using 75% of the copper of an equivalent single-phase system.

http://en.wikipedia.org/wiki/Split-phase_electric_power

old jim

 

[English Frank]

Hi Jim
Just one comment before I digest you full reply - The UK house supply is Line (230V), Neutral (0V) and protective Earth.
I appreciate that the N is probably grounded or Earthed by the supplying utility at their district transformer but never by the user.
Does this affect your main comments?

Youngish in spirit, Frank

 

[sophiecentaur]

I'm not a power Engineer so I can't be too sure but, without a neutral (I.e. a delta supply) you can't use a single phase without having it balanced. If you Earth one connection then the others will be higher voltage and with a bizarre 120 degrees between them. To overcome the lack of a neutral, won't you need another delta/star transformer?

 

[jim hardy]

I appreciate that the N is probably grounded or Earthed by the supplying utility at their district transformer but never by the user.
Does this affect your main comments?

no, you'll connect incoming neutral to either L1 orL2. It would be white wire here in US.

and safety ground to frame. That would be green wire here.

...

The voltage triangle will be equilateral with one point earthed.
120 degrees is complement of 60, extend your phasors?...

 

[jim hardy]

Draw base of 240 volt triangle two ways

1. earthed at one end (UK)
2. Earthed in middle (US)

then geometry gives phase to Earth voltages:

UK: 0, 240,240
US: -120, +120, 208

i think.

Need more coffee.

but if your load does not need that neutral wire, as a delta wound motor wouldn't, it need not exist.

old jim

 

[English Frank]

Late evening in England and my brain is in turmoil!

Notwithstanding the excellent advise I am receiving in these threads and bearing in mind that I am about to send a payment of $3100 to purchase the Phase Perfect PT330, I do need full assurances from Phase Perfect that this unit will connect to the UK power supply. The good people at PP state that I can hook 230v and a 0V Zero to inputs L1 & L2. but looking at figure 6 in the 'Operation and Installation Manual - PT Series' none of the three diagrams seem to show such a connection - or is this 'non electrician' missing something?
As a picture paints a thousand words, could somebody add the correct electrical symbols (diagram) representing the UK's 230V and 0V (neutral) to the inputs L1 &L2 of figure 1 and a representation of a 220V 3P motor (Delta) to T1, T2 & T3. I will then send this drawing to PP and request their confirmation that the US will not obliterate England when I switch on the installed PT330.

 

[jim hardy]

Late evening in England and my brain is in turmoil!

Notwithstanding the excellent advise I am receiving in these threads and bearing in mind that I am about to send a payment of $3100 to purchase the Phase Perfect PT330, I do need full assurances from Phase Perfect that this unit will connect to the UK power supply. The good people at PP state that I can hook 230v and a 0V Zero to inputs L1 & L2. but looking at figure 6 in the 'Operation and Installation Manual - PT Series' none of the three diagrams seem to show such a connection - or is this 'non electrician' missing something?
As a picture paints a thousand words, could somebody add the correct electrical symbols (diagram) representing the UK's 230V and 0V (neutral) to the inputs L1 &L2 of figure 1 and a representation of a 220V 3P motor (Delta) to T1, T2 & T3. I will then send this drawing to PP and request their confirmation that the US will not obliterate England when I switch on the installed PT330.

no, you are correct none of their drawings shows that.

I am an absolute klutz with drawing by computer. get too frustrated.
Were i home i'd draw it with pencil and paper, scan and post as a jpg for you.
But i am on grandkids' laptop 1000 miles from home...

Were i in your shoes i'd do the same thing you suggest , get them to say your intended hookup is okay first. You might even give them actual voltage readings L-N, L-G and N-G in your shop.

AND i'd suggest in a handwritten letter to their marketing director that they amend their drawings for UK customers.
Folks heavy into a subject, like they doubtless are, too often forget what it was like when they too were unfamilair with the details.
To them the phrase "give it zero and 240" is a complete answer but it leaves us outsiders encumbered by doubt.
Just look how many hours you have invested in understanding this. One picture is worth 10^3 words and it's an ounce of prevention too.

old jim

EDIT PS i applaud your thoroughness, and the understanding of electrical that you have demonstrated.
I suspect your woodworking shows similar attention to detail.
My daughter and i just refinished her Grandmother's dresser, hand built decades ago by Grandpa out of solid 1" walnut from the old farm in Missouri. I think you would approve.

old jim

 

[English Frank]

Thank you to all who have replied to this topic. I have now imported and installed the PT330 Phase Perfect phase convertor and it is working perfectly, in fact far more efficiently that the old static and rotary types generally found in the UK. As the output voltage of the convertor was designed for use in the US and its output is 240V 3-phase, I simply reconfigured the terminal links on my 3-phase motors from 415V to 240V.

 

[jim hardy]

Great news ! Congratulations to you sir !

and thanks for the feedback - news of a success is always uplifting.