Digital / Rotary phase converters - possible build

Hi all
I am looking at three phase conversion options for my workshop I have looked at rotary converters, and I have also looked at static and digital conversion options what I'm wondering is does anyone have a digital converter from the only manufacturer that makes them in this country that i know of, drives direct?
If so how well does it work and what is your experience with it?
I'm looking at getting 3 phase from the grid (extremely expensive 45k plus) and also looking at getting a rotary converter with digital phase balance. from the USA.
The other option is the phase perfect unit from the USA also, i have spoken with them and with the 480V split phase supply i have they said their machine will work for my needs.

The only other option I can come up with is to design and build a digital / rotary phase converter on my own, i have a lot of experience in electrics and electronics but cant figure out exactly how the digital phase converter works. The basis of it must be a VSD with Harmonic filter in front, and Sine Wave filter on the output side. And a bank of capacitors on the output of the DC bus to take the start current, also to get a Neutral you would need a Delta to Star tranny on the output side to get the neutral from the star point. But apart from that I'm not sure what else. And those bits alone in no way could justify the cost they charge for them in the UK.
Seeing one would help or any other suggestions.

I have as i say a 480v split single phase supply, which translates into 48kw single phase, so looking at the possibility of a full workshop 50HP converter, it would be right on the limit but would allow me to future proof the workshop incase i end up employing people going forward.

Thanks
Robert

robertlaurenson said:

Hi all
I am looking at three phase conversion options for my workshop I have looked at rotary converters, and I have also looked at static and digital conversion options what I'm wondering is does anyone have a digital converter from the only manufacturer that makes them in this country that i know of, drives direct?
If so how well does it work and what is your experience with it?
I'm looking at getting 3 phase from the grid (extremely expensive 45k plus) and also looking at getting a rotary converter with digital phase balance. from the USA.
The other option is the phase perfect unit from the USA also, i have spoken with them and with the 480V split phase supply i have they said their machine will work for my needs.

The only other option I can come up with is to design and build a digital / rotary phase converter on my own, i have a lot of experience in electrics and electronics but cant figure out exactly how the digital phase converter works. The basis of it must be a VSD with Harmonic filter in front, and Sine Wave filter on the output side. And a bank of capacitors on the output of the DC bus to take the start current, also to get a Neutral you would need a Delta to Star tranny on the output side to get the neutral from the star point. But apart from that I'm not sure what else. And those bits alone in no way could justify the cost they charge for them in the UK.
Seeing one would help or any other suggestions.

I have as i say a 480v split single phase supply, which translates into 48kw single phase, so looking at the possibility of a full workshop 50HP converter, it would be right on the limit but would allow me to future proof the workshop incase i end up employing people going forward.

Thanks
Robert

Click to expand...

Don't waste the scarcer hours of your life with "digital".

You have electron-pusher and DIY build-capability?

Build yerself a rotary.

AND NOT a single-idler "50 HP". You won't be able to START the f**ker off your single phase service!

Use a smaller pilot-motor idler with start and stop master controls.
Add "supplementary idlers" as the need grows.

Start modest. Run whatever you have.

As needs ACTUALLY expand, add idler motors. Stagger-start one or more add-on idlers that need only "locally attached" run caps so the balance follows which and how many are online.

Each supplementary idler needs but a 3-Pole contactor to bring them onto the line. I have NO clutches, ergo heavy starting loads.

Or drop them off.
My RUNNING loads are far lighter.

Only the pilot needs an RPC starter/control box

Wiring is BFBI simple.
Output is clean sine-wave.
No dv/dt or "Sine Guard" required.

Conversion efficiency? Well, there's a surprise for yah.

Neither of my old "blue case", nor still-here "white case" Phase-Perfect are exactly "magical" at conversion efficiency, after all. Annnnd . even the newer design, or most ESPECIALLY the newer design.. the MANUAL specifies replacing the capacitors at three-year intervals. After spending USD$ 4,000 for a ten HP?

My four-idler RPC scales to just under 30 HP and didn't cost but about TWO thousand, even with Reliance Duty-Master Extreme Service motors bought scratch & dent but otherwise never-yet-connected NEW as idlers.

Old body & fender guy can't fix a cracked or dented fan housing?
I should go back to riding a freakin' pushbike?

Not.



Nor is ANY other solution as cheap as an RPC, up-front cost-wise.

Nor as ruggedly "wire and forget" durable. 20 year run-cap change-out?

So I have BOTH!

And favour the RPC .... as gentler on really OLD load-motors..

My wallet at the head of the list as a "really old load"

Hi, Thanks for your reply.
I am in the process of buying machines, 1 being a new 3.5m cnc press brake, with a soft start 12kw motor and cnc controls, the other being a plasma table with a Hypertherm Powermax 105, with it's associated extract fan at 2.2kw. So with those two things in mind, and also the CNC router which has a 4kw spindle and 4kw vacum pump etc. I dont envisage running more than 1 or two at a stretch of these at any one time and with diversity the press brake and plasma should run fine on one supply, but the thing i keep hearing is about the CNC stuff not liking the unbalanced phases from a Rotary. Do you have a design you worked from to make it so it was balanced enough to run CNC gear? I have seen plenty of designs but the ghost leg is usually out far enough to make it an issue.
Also with my 480v split phase, i think i would need to transform it down to 440 ish, dont think there is any getting away from that unless you have another idea?
thanks
Robert

thermite said:

Don't waste the scarcer hours of your life with "digital".

You have electron-pusher and DIY build-capability?

Build yerself a rotary.

AND NOT a single-idler "50 HP". You won't be able to START the f**ker off your single phase service!

Use a smaller pilot-motor idler with start and stop master controls.
Add "supplementary idlers" as the need grows.

Start modest. Run whatever you have.

As needs ACTUALLY expand, add idler motors. Stagger-start one or more add-on idlers that need only "locally attached" run caps so the balance follows which and how many are online.

Each supplementary idler needs but a 3-Pole contactor to bring them onto the line. Or drop them off.

Only the pilot needs an RPC starter.

Wiring is BFBI simple.
Output is clean sine-wave, no dv/dt or "Sine Guard" required.

Conversion effiicency? Well, there's a surprise for yah. Neither of my old "blue case", nor still-here "white case" Phase-Perfect are exactly "magical" at conversion efficiency, after all.

Nor as cheap as an RPC, up-front cost-wise.

Nor as ruggedly durable.

So I have BOTH!

And favour the RPC .... as gentler on really OLD load-motors..

My wallet at the head of the list as a "really old load"

Click to expand...

Hi, Thanks for your reply.
I am in the process of buying machines, 1 being a new 3.5m cnc press brake, with a soft start 12kw motor and cnc controls, the other being a plasma table with a Hypertherm Powermax 105, with it's associated extract fan at 2.2kw. So with those two things in mind, and also the CNC router which has a 4kw spindle and 4kw vacum pump etc. I dont envisage running more than 1 or two at a stretch of these at any one time and with diversity the press brake and plasma should run fine on one supply, but the thing i keep hearing is about the CNC stuff not liking the unbalanced phases from a Rotary. Do you have a design you worked from to make it so it was balanced enough to run CNC gear? I have seen plenty of designs but the ghost leg is usually out far enough to make it an issue.
Also with my 480v split phase, i think i would need to transform it down to 440 ish, dont think there is any getting away from that unless you have another idea?
thanks
Robert

There are digital balanced rotary converters available here without going across the pond. I bought one for my dad's workshop pushing 10 years ago, made in England licensed from a NZ company.

Edit: Scratch that, it looks like they're out of business. It was a Digi-Phase, google brings up nothing but a dead site now.

gregormarwick said:

There are digital balanced rotary converters available here without going across the pond. I bought one for my dad's workshop pushing 10 years ago, made in England licensed from a NZ company.

Edit: Scratch that, it looks like they're out of business. It was a Digi-Phase, google brings up nothing but a dead site now.

Click to expand...

Used-but-good motors to use as idlers will be harder to source in Blighty than US or Canuckistan, though.

One land's junk, is another stan's treasure. So sharp, fast, and competent Paki entrepreneurs, some of whom I have met, snatch up all manner of still-useful goods and export them to North Africa or the less-affluent parts of Europe as soon as they come into view

Why not something like the Phase Perfect PT440R which run around $9.5K US, unlikely you will be using the full line load at any one time, so a 40Hp digital phase converter would seem practical. They tend to be reliable although they have their idiosyncrasies that others have posted. Voltage in is approximately = voltage out in 3 phase. Not sure how they would work in the UK because you are not using split phase and how that changes the input /output design, so best to work directly with Phase Perfect to see if they have a system that will meet your power requirements using your country specific power. I would think it is impractical to considering designing/building a digital system if you need to be up and running reliably.

If you have single phase over there, you have a different system to ours. Yours is hot and neutral, while US 240V single phase is two hot wires, with center tap ground.

So for us, we start with single phase of the voltage wanted, and need only create one phase wire. We start with two wires of the delta system. That is fairly easy.

We have 480V 3 phase systems that are 277 V from hot to neutral, and we have 208V 3 phase systems that are 120V hot to neutral. In those cases, there is no need for converters since the 3 phase is already present, and converters are not made. There is no "distribution" of the 277V as a single phase, and 240V 3 phase is somewhat obsolete, although it is available and called "farm", "high leg", or "lighting tap" 3 phase.

Your issue is different, since you need to create 2 phase wires, from one wye voltage. I assume you want to end up with 415V 3 phase. Standard US phase converters are not set up that way. A "static converter" simply does not work for that, and a rotary is very inefficient for it (I have set up that system as a test).

If your motors can be reconnected from 415 to 240V, then you have a different problem, and it is much easier. A regular US style rotary or static converter will work, you would end up with the same setup as "corner grounded" 240V 3 phase, which our power companies no longer supply.

Which system do you need?

JST said:

If you have single phase over there, you have a different system to ours. Yours is hot and neutral, while US 240V single phase is two hot wires, with center tap ground.

So for us, we start with single phase of the voltage wanted, and need only create one phase wire. We start with two wires of the delta system. That is fairly easy.

We have 480V 3 phase systems that are 277 V from hot to neutral, and we have 208V 3 phase systems that are 120V hot to neutral. In those cases, there is no need for converters since the 3 phase is already present, and converters are not made. There is no "distribution" of the 277V as a single phase, and 240V 3 phase is somewhat obsolete, although it is available and called "farm", "high leg", or "lighting tap" 3 phase.

Your issue is different, since you need to create 2 phase wires, from one wye voltage. I assume you want to end up with 415V 3 phase. Standard US phase converters are not set up that way. A "static converter" simply does not work for that, and a rotary is very inefficient for it (I have set up that system as a test).

If your motors can be reconnected from 415 to 240V, then you have a different problem, and it is much easier. A regular US style rotary or static converter will work, you would end up with the same setup as "corner grounded" 240V 3 phase, which our power companies no longer supply.

Which system do you need?

Click to expand...

I am in a bit of a special scenario. I have single phase 480v, single phase 3 wire, same as the USA, 240v hot to neutral, 480v hot to hot, same as you describe above.
So looking at the Phase Perfect system, the 480v option, with a Delta to star transformer on the output side to give me the 440 i require.
You are right in what you say, most single phase connections in the UK are a live and neutral. But i have as i say 3 wire system 2 live and a neutral from a center tapped transformer. So with that the PP system should work just fine.
Thanks
Robert

Wild.... but you are correct. All standard US type solutions will work for you as they do here.

robertlaurenson said:

I'm looking at getting 3 phase from the grid (extremely expensive 45k plus) and also looking at getting a rotary converter with digital phase balance. from the USA.
The other option is the phase perfect unit from the USA also, i have spoken with them and with the 480V split phase supply i have they said their machine will work for my needs.

The only other option I can come up with is to design and build a digital / rotary phase converter on my own, i have a lot of experience in electrics and electronics but cant figure out exactly how the digital phase converter works. The basis of it must be a VSD with Harmonic filter in front, and Sine Wave filter on the output side. And a bank of capacitors on the output of the DC bus to take the start current, also to get a Neutral you would need a Delta to Star tranny on the output side to get the neutral from the star point. But apart from that I'm not sure what else. And those bits alone in no way could justify the cost they charge for them in the UK.
Seeing one would help or any other suggestions.

Click to expand...

If you can spend the bucks, or the pounds, then a digital phase converter like a Phase Perfect.

If you want to try building something then it's not so hard. Except for the high voltage electronics. I did buy a surplus VFD and built this circuit
that generates the 3 phase wave forms. The idea is to use the high voltage switch devices and trigger them with my stuff. I used a $10 NXP LPC1768
demo board and some logic around it. My software algorithm uses Space Vector PWM. Just involve turning six switches on and off at the appropriate
times and intervals. I wrote down the vector equations and derived the software interrupt routine. Just involves six states with one output changing
each interrupt. If you do something like this the hardest part will be figuring out what kind of feedback to use, if the thing was to be used as a VFD
with changing frequencies. Using it as a RPC with a fixed frequency and your only hard part is the high voltage stuff.

robertlaurenson said:

So with that the PP system should work just fine.

Click to expand...

It is even covered in their manuals.

So, too paralleling and slaving for expanding capacity.

Potentially useful if you have a(ny) option to start small(er) and grow large(r).

But CAVEAT: Old and new models have so far NOT been rated for mixed-rev arrays. At all.

My manuals came with each of the two P-P, but I'm pretty sure you can get those FROM Phase Technologies before you make the "buy" decision.

Worth it, research and planning is.

"Cheap" their goods were never.