Digital vs Rotary phase converter - possible build

[robertlaurenson]

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

 

[nickds1]

Hi. Another electronic engineer here.

Designing and building a safe 50HP / 40kw single -to-threephase digital converter is a hugely specialised job that, personally, I wouldn't touch with a barge pole. Unless you are a design engineer specialising in serious power electronics, there are just so many ways this could go very badly indeed, leading to fire, serious injury and even death. If there was an issue, I'm not sure what your insurers would say.

If you've done this before, I apologise for stating the obvious.

 

[sawtooth-9]

I agree with nickds1
It is really an area I would never entertain ( even though I have had 30 years experience working with an industrial sparky ! )
At 50 KVa, you are talking serious stuff.
Are you sure you need this capacity ? I guess it depends on how many machines you will run at one time. If it's a "one man show " I doubt you would need that much power at any given time.
I was faced with the same problem, moving into the Aussie "bush". Far too expensive ( around Aus$ 80,000 )to get 3 phase from the grid.
I was faced with a simple choice - convert all my machines to single phase or generate my own 3 phase power.
It was miles cheaper to buy an almost new Kubota Super quiet 20 KVa diesel generator !
Belt a good earth stake into the ground and stick in a simple sub- board for the workshop, and it's done !
The cost per KW hour is higher, but you don't have the capital outlay. That capital outlay pays for a LOT of KW hours !
If you go down the route of generating your own power, just ensure you get a generator capacity that will cope with the starting current of your largest induction motor.
Good luck !

 

[Sideways]

In the context of this web forum, 48kW is a heavy weight supply. That's multiple 5kW loads all running simultaneously in what presently appears to be a one man shop just in case you end up employing some people.

You are referencing a tiny UK firm that looks to be primarily reselling Teco Westinghouse products and is being allowed to put their own label on a few Teco manufactured products. I presume that this is because they mention in their list of references:
"480V Split Phase can be converted to 415V 3 Phase" and you have this specific requirement.

A 480v split single phase supply isn't something that most people will ever have heard of. It's described here:
https://www2.theiet.org/forums/foru...=102842&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear
Basically two 240V phases L1 and L2, with a 180 degree phase difference and a common neutral. It is normally found in rural settings where power cables are run above ground on poles.

Nothing about the Drives Direct website suggests to me that they design or build digital phase converters in the UK (transwave type are a different matter, I could build one in my garage), but at least the largest Teco units they list are roughly the right size for your requirements.
I'd suggest that you contact a few manufacturers technical support lines, describe your need and ask if they offer a product. If DD say they can do this and they mostly sell Teco, then perhaps Teco devices support this input. Others may too and this will give you more choice to find a better price.

Alternatively, just treat your split phase supply as 2 separate 240V single phases and spread your loads across two smaller (though 100A input is hardly small for most readers) phase converters. That would also give you diversity in case one were to fail rather than having all your eggs in one basket.

As another electrical engineer, I am confused by your idea of a DIY build.
You have "a lot of experience of electrics and electronics" but you can't figure out how a digital phase converter works ?
You are asking for advice on a forum that really isn't the obvious place to ask for specialised electronics design advice.
I must (politely) wonder about your abilities to design and build a DPC cost effectively, especially one that big.

For others reading with lesser requirements, my own first hand experience is limited to installing just one of the chinese digital phase converters readily available on ebay. It is a 3.5 or 4kW unit, far better than the transwave it replaced but the ratings are aspirational. If you shop for one, personally I would buy 2 sizes larger than their specifications suggest. 162 page manual and no harder to install than a proper VFD.