3 Phase converter

[Pete.]

I'm sure that there is no need for that. People can disagree and still play nice without getting super-defensive or descending into personal attacks.

The fact that you have encountered similar reactions from several forums just serves to reinforce that people don't simply accept that something is the next great new thing without some technical detail to back it up, and nor should they in my opinion. I certainly wouldn't.

You say that your transformer has a total of only three connections? That makes it a non-isolating autotransformer. I use one of those myself to boost 240v mains to 290v for my Monarch lathe's DC drive. There's very little new in the world of transformers and windings. It could be that this guy Doug has found a new way of implementing it in a way that makes it easy for the layman to utilise but without seeing some sound basic technical detail you're not going to convince folk that simply connecting a transformer in a particular way is going to yield 3 phase from single (especially now that Jim has come along to say that the 3rd leg is manufactured by the motor).

I think that you would be doing Doug a much greater service by describing the sound theory behind the system without giving away the small details, if you're going to promote it for him. If people see a value in the theory, they'll be more happy to part with money for the literature.

Pete.

 

[Bushy_1]

If it works so flawlessly, why does Doug not have them manufactured and sell them? I think there would by a big market for a solution to 3 phase.

 

[maz0]

If it works so flawlessly, why does Doug not have them manufactured and sell them? I think there would by a big market for a solution to 3 phase.

Probably because they are deadly.

 

[Retired]

Hi,

Thanks everyone for your replies. A special thank you to you Pete; yes looking at some of my comments they are out of character for me and read as unfriendly so I'm sorry for this as I never intended offence.

I understand all the curiosity and an excellent question you asked Bushy as to why Doug doesn't build and market the transformers; Doug is happy just marketing his idea and seems content to leave it like this?

I'll lighten up a bit because as I stated I don't wish to break copyright rules and I certainly don't wish to being dragged into any unpleasantness. It's so easy to assume this transformer has just two windings; primary and secondary which any basic transformer needs in order to work; please have a look at the first picture I added in post #6 and although the laminations are from a 3 phase transformer the original windings I removed then note only two of the legs are wound and further note the numbers of wire tails; there are two primaries and a number of secondary coils; the unique part is how the coils are connected and get these wrong it trips breakers; Doug wouldn't be calling his method unique if it wasn't and anyone can buy Doug's instructions cheaply enough then if they want to post the details on an open forum it's their choice.

Generally I'm very polite and helpful adding lots of information as seen in many of my posts but I couldn't stand by without defending Doug in his absence; my unfriendly comments were aimed at only those being rude to Doug without first gathering all the facts before condemning Doug's excellent method; Doug also gives a great deal of information on how to make your own rotary converter and also a welder; my only interest was the transformer method.

I was just going to post when your message popped up maz; yes these transformers will be hugely lethal to play with by any novice and I certainly don't encourage anyone without electrical safety knowledge to go near one. They are complicated to wind; the friend I sold my transformer to has been a sparky all his working life but he tried to wind one of these and failed for some reason hence he jumped at buying mine because had seen it many times in action.

I will answer the question as to wire used because I can state the wire sizes only for my laminations and each transformer will most likely be unique so nothing being given away; 1.5mm & 2.5mm household single insulated conduit wire bought from Screwfix. Turns ratio as per Doug's instructions.

Sorry once again for my impoliteness.

Kind regards, Colin.

 

[Hopefuldave]

I'm sure that there is no need for that. People can disagree and still play nice without getting super-defensive or descending into personal attacks.

The fact that you have encountered similar reactions from several forums just serves to reinforce that people don't simply accept that something is the next great new thing without some technical detail to back it up, and nor should they in my opinion. I certainly wouldn't.

You say that your transformer has a total of only three connections? That makes it a non-isolating autotransformer. I use one of those myself to boost 240v mains to 290v for my Monarch lathe's DC drive. There's very little new in the world of transformers and windings. It could be that this guy Doug has found a new way of implementing it in a way that makes it easy for the layman to utilise but without seeing some sound basic technical detail you're not going to convince folk that simply connecting a transformer in a particular way is going to yield 3 phase from single (especially now that Jim has come along to say that the 3rd leg is manufactured by the motor).

I think that you would be doing Doug a much greater service by describing the sound theory behind the system without giving away the small details, if you're going to promote it for him. If people see a value in the theory, they'll be more happy to part with money for the literature.

Pete.

I agree, if Doug has genuinely come up with something novel he'd be wise to patent it PDQ but that would open it up to non-commercial users replicating what he's done - would prevent others selling the info or copying his idea for profit, so he'd be quids-in.

I also use a transformer to get from 240 to 415, and a number of windings on the secondary side to adjust the output voltage BUT it's an isolating transformer as that's just good practice for high-power, high-voltage supplies.

Winding the secondary - turns ratio was worked out by winding a few turns through the core (an old oil-cooled welder rated for 9 kva on 240v) before stripping the welding current winding, dividing the voltage by the number of turns (and finding it gave root-3 v/turn, convenient!) yielding a 240-turn secondary, a couple of extra secondary windings to allow some "fine" adjustment (for 5 and 10 volts addition / subtraction) - coil winder was cobbled together from available workshop bits and looked like this:



Being a bit, er, fussy, I vacuum impregnated the secondary with epoxy in a plastic bag with Lucky (vacuum bleeder...) and a kg of resin to prevent extra vibration / noise and fatigue of the winding wire.

That got 415, the 3-phase was by rotary convertor, with the usual "balancing" caps. I went a bit OTT with the control panel, hatful of contactors etc.

Power plane:

Control plane:

The contactors are interlocked so it has to be started in a sequence: mains on, motor on, output on (so inrush currents aren't all pulled at the same time), input overcurrent, motor overcurrent and output faults (RCD or MCB trips) take it back to the beginning again with an appropriate fault lamp lit (long arm microswitches bolted to DIN rail spacers with a cross-bar hit by the levers when they trip).

Ended up as (excuse the isolator missing its handle!):



I like safety... Just my way of doing it.... Anyone's welcome to copy it should they be daft enough!

Dave H. (the other one)

 

[Retired]

Hi,

Very well done Dave H and very well thought out and such a neat job. I too like safety and playing around with mains electricity for a novice is definitely asking for a short lifespan. Thanks for posting your interesting circuit diagrams. I was daft enough to succeed with the transformer method.

Doug's transformer method supplies the 3 phases without need for a donkey motor at any voltage. Surge at times was a slight problem; powering up such a big transformer occasionally tripped the CU mcb but if I reset it immediately and switched on again the transformer always fired up.

I didn't establish the turns/volt ratio whilst stripping the transformer but just followed Doug's very detailed instructions and achieved 1.5V/turn this being perfect. I can say this heavy transformer idled at only 0.8A; playing with the primary turns altered this quite a lot but at 1.5V/turn it proved the optimum.

I sussed out years ago how to determine the turns ratio of vintage radio transformers because I started to rewind transformers finding it much easier than expected once I grasped the basics; a vintage radio mains transformer has a number of tappings and all I needed to do was to locate ether the valve heater or panel lamp secondary tapping with the thicker gauge wire and count the turns as I unwrapped; a panel lamp at 6V if unwrapped gave 24 turns then the ratio was 1V/4 turns; supply was on 240V and this gave the primary at 960 turns; the secondaries were equally easy to work out at any voltage; rewinding was easy because I already had the original wire to measure the gauge of and the gauge was critical; the turns had to fit into the lamination window.

I used to wind tuning coils; output transformers; inter valve transformers and field windings.

Once Doug's method is installed and fully commissioned then switch on the transformer and switch on the machine/s needed; 3 phase laid on with full power starting even under load. It is impressive to see this in action. I was happy to buy Doug's information because I think the DVD's gave about six hours viewing; it's many years ago I installed my 3 phase; it was scary because I'm not a sparky although I've done lots of electrical work especially wiring motors; being so near a big transformer powered up testing volt/turn ratio I did wonder about flash over so I was always well insulated and as with my vintage radios working with one hand; many vintage radio chassis are live and to pick one of these up with both hands whilst powered would be the last thing ever picked up.

It's unlikely Doug's transformer method will ever go into production due to start up costs and all the H&S regulations; these transformers definitely work but then phase balancing each machine to the transformer would be a real problem for a manufacturer to sort out; I worked at Brook Motors for 24 years and the equipment involved in making the motors was eye wateringly expensive; the headquarters I worked at put out at its peak around 1,350 assorted motors each day.

I'd like to make it clear that I've never suggested anyone dash out to buy Doug's information all I wanted to do was to make members aware of its existence; no one told me about it so I went in blind and paid the money which I've never regretted; what can you get these days for £17? I've just been looking at notes I have on file; on March 27th 2009 a guy in Wales contacted me he having been quoted £17,472.35 to have his two farm houses wired with mains 3 phase 415V my transformer was completed including buying the scrap transformer for just under £120 and I got this back when I sold the transformer; I could wind lots of these transformers assuming I could buy scrap doner transformers and sell them on but then I'd be in a whole lot of trouble should someone be electrocuted because although the transformer supplies the 3 phase each machine needs to be balanced; what a terrible thought so what I'm posting is not intended in any way as being tutorial and anyone attempting such work does so entirely at their own risk; it's just scares me that Doug is selling such highly dangerous information to anyone handing over a small amount of money. It is definitely dangerous.

I once ruined a big old cast iron 3 phase 415V motor removed from a Wadkin woodworking chop saw; at the time I didn't have the 3 phase transformer and had been reading about star/delta motor wiring; modern motors have the six wires very accessible but these old motors meant solely for 3 phase 415 had their star point buried and if the star point could be located then this gave the other three wire ends allowing the motor to be connected in Delta then I could add start & run caps powering from single phase 240V; I only ever tried finding the star point once but others I know have succeeded.

Kind regards, Colin.

 

[Dev]

How much have you chaps spent on getting a working converter in terms of time and materials?

 

[Hopefuldave]

How much have you chaps spent on getting a working converter in terms of time and materials?

I dread to think...

The motors I used were £70 on EvilBay, 415v 5.5 and 3KW, transformer was an old oil-cooled welder rated at 9 KVA for £20 on EvilBay, probably another £60 on enamelled copper to rewind it, contactors, RCD, MCBs were from the junk box, cheap Chinese volt and current meters, ditto pushbuttons, EvilBay big capacitors - I'd guess about £200 plus a fair few evenings' head-scratching and building - a VFD would have been cheaper BUT... I'd have needed three for my mill, plus a big DC supply for its clutch/brake, and I wouldn't be able to plug my 3-phase TIG or future purchases into them!

I have drawings, posted above, for my OTT 240 to 415 convertor...

Dave H. (the other one)

 

[Memmeddu]

That's is the wiring diagram of how should turn mine
Little bit easier design and no transformer
Another thing that I thought is try different legs configuration in the input side to find the best
(Lower voltage difference read between each phase)

 

[HughF]

How much have you chaps spent on getting a working converter in terms of time and materials?

I think my 15kW boost cost me around £400 by the time I had put a new set of shift caps in it...

 

[HughF]

The book is £11 on amazon, I might scan it and upload it