Magnomatics’ patented Pseudo Direct Drive (PDD®)

Topic split from: Random Engineering, Physics, ..., Concepts and Ideas

The PDD essentially just a magnetic clutch inside an electric motor, rather than external to the motor. Its rather like a stepper motor in function. What exactly is the revolution here?

As for the self-driving car that demos drift-racing action; that’s not really related to AWES engineering, just a more complex way to burn up tires.

I think you have mis understood the technology, this could replace a mechanical gearbox in a winch drive train giving superior efficiency and service life as well as avoiding the mechanical vulnerabilities of conventional multiplication gearbox. This is cutting edge technology which is being employed in some of the largest HAWTs under devlopment. It could provide a efficient, reliable, simple and compact drive which could offer significant LCOE benefits if employed in a AWES and scaling potential.
How can you possibly dispute the potential of this technology in AWES?


No, I do understand the advantages these engineers are seeking, by integrating the functions of magnetic drives.

The point is that a marginal improvement in standard mechanical engineering does not mean much to AWE as such, which can use the same gearing that currently runs the world, or adopt improved versions as the market selects them.

The finest AWE demo may use the cheapest crudest elements in a superior way. The landscape is littered by AWE prototypes made from the most advanced parts, but lacked inherent capability.

Windy skies has closed this topic, so pasting censored content here-

I am not negative. Truly solving AWE is the most fantastic engineering challenge of our time. I am indifferent about whether magnetic drives are an economic option. What most excites me is the existing mechanical interface to legacy GW-scale generators. Lets drive that, as a positive goal.

Compare this magnetic drive with kite tech rope drive equivalents, by the metrics of power-to-weight, cost, and complexity.

I realise that at small scales and for short service life prototypes conventional gearboxes are to obvious choice, but as I said before the ‘future’ which can be looked at in terms of a competitive LCOE, reduced OPEX, CAPEX and improved yield over a commercial systems life are very important to the ‘future’ of AWES.
Why be so negative?

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I think in the debate between mechanical gears and magnetic gearing there are a number of things that the magnetic gears can offer. For instance multiplication gearboxes and vulnerable to inertial magnification between prime mover and armature putting the output gears under extreme stress when the prime mover suddenly accelerates, a lot of early large wind turbine gearboxes failed due to this and a yo-yo style system will experience a lot more acceleration. The solution to wind turbine gearboxes was flexible shaft designs and this may transfer to AWES systems or not, however the magnetic gears do not have this design risk. The magnomatics engineers also indicated to me that the gears could be made to freewheel almost instantly which could be very valuable in failure mitigation and also if the design requires two ratios, one for retract and one for generate; thegenerate side could freewheel in retract. I think also that 97.5% drive train efficiency is a fantastic number which is perhaps 5% higher than a gearbox generator combination over lets say a 25 year commercial device life that is a tremendous amount of additional yeild


This is very good stuff. The inertia issue is indeed probably quite grave for Yoyo. I am not an expert in motor/gearboxes, so I will refrain from further comments

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2.5% less drive power is quite a loss, if it can be avoided by design. Same applies to gear loss.

Fortunately, kite pumping loads are relatively shock-free, given the inherent elastic properties of wind and polymer.

Thanks for this, Windy Skies. As someone designing and manufacturing PM generators for most turbines we’ve sold from this shop over the years, I’ve been intrigued with the possibilities of this sort of effect. One of the first challenges you encounter is how to reduce or eliminate “cogging” (gear-like resistance to rotation) which impairs easy startup and smooth operation in wind turbines. Currently helping a major manufacturer reduce their problematic cogging, in fact.

But what about using the effect rather than eliminating it?
I had assumed I must not be the only one considering such concepts, but had never heard it mentioned until now. I must say, it gets to be a real brain-teaser trying to envision exactly how something like this might work. In my case, besides for wind energy, there is another gear system in common use that I keep thinking might be replaced by something like this. I might have to twist my feeble brain into a pretzel, at least, maybe a double-pretzel, to fully grasp the details of exactly what this website claims to have developed, but their basic unit is almost identical to my sketches in most ways.

Is this “company” for real? Does everything they talk about really work as advertised?
We might note, the info on this website is a couple years old now. Click on “Latest News” and all you find is a statement of one more proposed use for the general idea, but no real “news”.
Checking (Wayback Machine), Magnomaatics’ website announcing magnetic gears has been around since March 2007 (13 years ago?), yet we do not see any working model on their website today, just renderings and claims about how well the ideas work, as though they actually exist. The five “Articles in the Press” are all over two years old.
My questions include:

  1. Will the device(s) work as claimed?
    a) Would they achieve the cited ratios, in real life?
    b) Would they achieve the cited efficiencies, in real life?
  2. Have any of these been built and run?
  3. Are any in use today?
  4. Have other entities pursued these concepts?

Given the simplicity of building something like this, and the apparent usefulness, it would seem surprising if nobody has worked on it.
OK I googled magnetic gears.
There’s a lot of theoretical musing, but a brief search by me did not see any in use.
Well, it’s an interesting and intriguing idea.

In my conversations with them, they indicated they had a number of devices operating on test beds, and there were existing devices available for experimental use almost straight away I think there was one ~300KW, I do not know how many hours they have been run for. I am confident that they have been operated successfully and they are set up as a manufacturing outfit. I think the reason they have only appeared as a company in the last 3 years is that it was a university project for quite a while before hand.
Will the claims pan out? impossible to say! However if they do it would be a significant step forward in drive train technology which don’t come along often, so lets hope they do.

These motors appear a few times a year, then disappear without a trace. It could be some develish details in there, or just the fact that introducing a new motor into a mature market is very difficult. Kitemill’s partner FECreate are developing a compact motor. Though quite different to this design, their design also provides some substantial improvements over the current status quo. They are also testing their unit these days.

I think it quite likely that one day one of these products will make it to the market. The kite winch is not the most unlikely market for this to happen, if AWE with winches took off.

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You’ve been claiming power-kites will drive existing power-plant GigaWatt generators for many years now. I see it as 100% delusional. These existing very powerful generators operate at a ~constant RPM, and require an immense amount of concentrated power to spin them. Sorry, but I do not see how “power-kites” could fit the requirements of driving such a generator. Maybe you ought to try to demonstrate a way to use your power-kites to drive a smaller grid-tie generator first, before making such outrageous claims.

AWES prototypes represent an ideally novel demo app for novel drive-train tech. This is the nature of the narrow opportunity for both technology domains. The PDD would be a good fit with kPower AWE R&D, even if it never catches on.

Future industrial AWE will adopt whatever electromechanical basis is standard in its time, for lowest LCOE.

I liked the FE Create integrated motor and drive for is compactness and efficiency, my concern is that the motor is quite high speed and would require a large multiplication ration in the gearbox and along with the 2 speed gearbox design I have some doubts about how vulnerable the gearbox might be, of course I am speculating some what not knowing the exact details of how the FECreate gearbox actually works. Still a 2 speed design would have practical advantage is optimising generating cycle timing and minimizing drive hardware.
Of course the vulnerabilities might only appear when the design scales up significantly.

Reading their website more, it says under “applications” that they do have a unit operating down-hole in an oil well to drive a pump. Well at least that is what they say… I’d be more comfortable believing the rest of the “applications” if they included some real videos (not just animations) of this breakthrough in actual operation. If they have an automotive drive, why not show the car being driven? If they have a marine drive, why not show the boat underway? It makes me wonder how much of today’s misdirected “bubble” of investments in technological missteps could be a result of the profusion of computer rendering? Still, I find this general idea intriguing.

I wonder if a magnetic flywheel could be included in the magnetic gears in order to provide a constant RPM for the yoyo system even during reel-in phase, while a motor would be used to recovery the kite.

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I know they are aware of these issues and working with different configurations. Other than that I dont know the details

Some more in depth technical reports:

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Here are some various links to try to complete a bit the fine files and explains from @George : : page 8, flywheels on figure 10 a and b.

Below is a video of Magsplit (an implementation of a flywheel is mentioned at 8’15"). : this is a download page for short documents of which a paper about Magsplit: MAGSPLIT Data Sheet.pdf (548.1 KB). From the last linked file: “In-built torsional compliance reduces drivetrain pulsations – remove flywheels and torsional dampers”. However the implementation of a flywheel may be necessary or useful to fill the reel-in phase. And such an implementation looks to be studied for some uses of which transports (video and figure 10 a and b). Please what do you think about it @George?

Thank You George and Pierre!