Brilliant $100M switched reluctance motor - Page 1
Forum section: electronics / general

author: JohnG
author_rank: Frequent Contributor
timestamp: March 05, 2021, 01:59:10 pm
content: Read it and weephttps://techcrunch.com/2021/03/03/firms-backed-by-robert-downey-jr-and-bill-gates-have-funded-an-electric-motor-company-that-can-slas/This idea is brilliant.Not the motor. Not much new or special there. It's the selling of it to rich investors for so much money. That's what's so brilliant.Cheers,John

author: jonpaul
author_rank: Super Contributor
timestamp: March 05, 2021, 10:20:52 pm
content: I believe its for 3 phase for HVAC, not avail to general consumers or for fractional HP eg single phase.Believe its most usefula > 1 HP and for variable speed and load not fixed like water pumps or circulators.Nikola TESLA (NOT THE CAR) invented the Induction motor (and AC synchronous motors and generators ~ 1885 in Budapest.Kind Regards,Jon

author: David Hess
author_rank: Super Contributor
timestamp: March 06, 2021, 05:11:22 pm
content: Motors reached the point of diminishing returns in efficiency long ago, so any advantage here is in variable speed operation which other motor types support as well. Variable reluctance motors do not require rare earth elements which is nice but neither do induction motors.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 07, 2021, 03:16:06 am
content: Reminds me of that Steorn Orbo scam a bunch of years back. I recall it was a... broadly similar thing, switched reluctance, with the claim that the energy used by the electromagnets is independent of load, and approaches zero (a casually plausible claim, but easily disproved).In this case, I wonder what they're doing about core loss. At, apparently 20kHz, that's a lot of switching for one, and implies ferrite or other high frequency core materials. Which implies torque is even lower (low Bsat), on top of already being low due to the limitations of switched reluctance in the first place. Hard to say, there's very, very little technical detail in the video.So, at this point I would have to agree, it's an, apparently, so far, exquisite grift, just fancy enough to hook some big names, presumably actually giving out big bucks.Tim

author: floobydust
author_rank: Super Contributor
timestamp: March 07, 2021, 03:37:08 am
content: The rare-earth wars have yet to start, that and lithium might stranglehold manufacturers, as everyone and their dog is on the bandwagon to make electric vehicles.I would see switched-reluctance having a role and the power semiconductors are up to speed, so to speak. Axial flux and large diameter rotors are used to get more torque with less Bsat. I think cars have the room.But $180M in financing acquired, to make an electric motor? Really? It's going to be another bubble stock in the giant EV bubble. Just a reminder Tesla market cap is $574B...It's a strange time to be an engineer.

author: Circlotron
author_rank: Super Contributor
timestamp: March 08, 2021, 12:24:55 am
content: Decent size high quality induction motors have efficiencies approaching 96%. So much for switched reluctance motors saving 2/3 of the power or whatever. See page 9 ->https://tic.toshiba.com.au/premium_efficiency_heavy_duty_induction_motors/Catalogue%20Toshiba%20LVM%20Premium%20Efficiency.pdf

author: langwadt
author_rank: Super Contributor
timestamp: March 08, 2021, 12:32:12 am
content: “We’re pulsing in precise amounts of current just at the times when you need the torque…"so like almost every other motor with a controller

author: WattsThat
author_rank: Frequent Contributor
timestamp: March 08, 2021, 01:48:10 am
content: “We’re pulsing in precise amounts of current just at the times when you need the torque…"Yeah. That’s exactly how the ABB Direct Torque Control algorithm works with standard induction machines. It has been around commercially since 1995.Woop tee friggen doo.Just another example of reinventing the wheel with the sole purpose of sucking cash out of willing idiot investors, all in the name of saving the planet. Fools and their money are soon parted. Unfortunately, government is at the front of the line to give the money away.

author: JohnG
author_rank: Frequent Contributor
timestamp: March 08, 2021, 02:18:42 am
content: In this case, it's not the government, but private investors. While the government has made some pretty big mistakes (Solyndra, anyone?), a lot of those had a better technical story, it just did not pan out.But this one? Motors are already very efficient, the power electronics and control is well established, if not necessarily well understood by most. Even though the rare earth angle is important, induction motors can tackle that, and more advanced induction motors are in the 90+ % range even with variable speed control. Switched reluctance definitely has some benefits in terms of simplicity of motor hardware, but the controls are a challenge.But, the efficiency gains they claim are already there or close with existing motors and drives. There is just not that much gain to be had. The HVAC angle is strange because fans and pumps are a pretty benign load compared to vehicles.It's the dollar amount that gets me, and it means that the funders do not have even a half-way decent means of evaluating technology.Sour grapes, you say? Damn right!Cheers,John

author: bdunham7
author_rank: Super Contributor
timestamp: March 08, 2021, 02:56:03 am
content: Quote from: Circlotron on March 08, 2021, 12:24:55 amFor larger sizes and at greater expense, yes. But it is difficult to maintain that efficiency when you factor in variable speed and smaller sizes. For household-sized motors and slightly larger--like pool pumps, HVAC fans, etc, the best current high-efficiency replacements are permanent-magnet 'ECM' motors and the appropriate controller. I've installed a few in my house and they have shown significant reductions in power usage compared to the best PSC motors available for their applications. A switched-reluctance motor would have all of those advantages without rare earths, so I'm looking forward to their wide availability.That said, the marketing wank in the video was nauseating. Practical switched reluctance motors may be new-ish tech, but they aren't emerging tech. My car has such a motor and that design has been out now for nearly 10 years. Probably the only reason we haven't seen them in smaller applications is that the rare earths haven't become unobtanium yet. If they do, everyone will be building the switched reluctance variety. I can't comment on the investment side--the whole market--VC and otherwise--is totally insane at the moment. Still, it costs money to set up manufacturing at scale and their videos seem to reflect a pretty small operation. I just hope their plan isn't based on some huge price premium for their product.

author: SilverSolder
author_rank: Super Contributor
timestamp: March 08, 2021, 04:19:04 am
content: Quote from: bdunham7 on March 08, 2021, 02:56:03 amKeep hitting the "Print" button, and you can invest in anything!

author: f4eru
author_rank: Super Contributor
timestamp: March 08, 2021, 07:34:45 am
content: Quote from: bdunham7 on March 08, 2021, 02:56:03 amDon't worry. Their plan is to get VC money and party like there's no tomorrow until it's completely gone.

author: Nauris
author_rank: Regular Contributor
timestamp: March 08, 2021, 05:46:58 pm
content: Quote from: bdunham7 on March 08, 2021, 02:56:03 amThat kind of motors actually rarely employ rare-earth magnets but instead ferrite magnets are most often used. Most applications really don't need the power density rare-earths can provide. Ferrite has the advantage of being much cheaper, composed of only common and widely available elements and having much better resistance to high temperatures.

author: madires
author_rank: Super Contributor
timestamp: March 08, 2021, 06:08:41 pm
content: Quote from: langwadt on March 08, 2021, 12:32:12 amYep, old wine in new skins. Add some buzzwords and get millions from investors. What a waste of resources!

author: Kleinstein
author_rank: Super Contributor
timestamp: March 08, 2021, 06:25:16 pm
content: The switched reluctance motors are kind of directly competing with brushless permanent motors. They are quite similar in many aspects (e.g. similar electronics, variable speed, good efficiency).I have heard of a few applications for switched reluctance motors: There are a few premium (e.g. $1000 range) shop vaccums that use such motors. There are some special higher power (e.g. 10-100 kW range) air compressors (actually turbines than). There were some plans using it in wahing machined as a possible larger market - not sure if this really is a big deal.The circulation pumps (some 10-50 W range) for water based heating systems as usual in Europe are quite a market. Here variable speed helps and modern electronic pumps can be really more efficient (e.g. some 10 W instead of 50W). So far I have seen the brushless with magnets here - in this use they may actually use ferrite magnets, despite of slightly lower efficiency.The Nd magnets are not that expensive anymore: for the same magentic energy (B*H) it is a similar price range as the ferrite magenets. So it is no longer a real premium price, just new and more sensitive to high temperature and corrosion.Nd is a rare earth element, but these are not at all rare elements. It is just the chemical treatment that is dirty and a bit expensive.

author: Nauris
author_rank: Regular Contributor
timestamp: March 08, 2021, 08:40:47 pm
content: So far I have only seen rare earth magnets in some A/C compressor motors (there were about 100g), everything else is basically using ferrite magnets. I think there is the political risk, volatile pricing and tightness in supply that they are not used unless necessary.In some datasheets, there are even declarations like this:"Only ferrite magnets and not rare earth magnets are used in externalrotor motors from ebm-papst Mulfingen GmbH & Co. KG"

author: floobydust
author_rank: Super Contributor
timestamp: March 09, 2021, 08:04:21 am
content: The original Tesla Model 3 was an induction motor, but may have been abandoned due to the low efficiency regen.Now, it is "IPM-SynRM motor (Internal Permanent Magnet - Synchronous Reluctance Motor), known also as PMa-SynRM Permanent Magnet Assisted Synchronous Reluctance Motor."

author: SilverSolder
author_rank: Super Contributor
timestamp: March 09, 2021, 01:17:35 pm
content: Great video. I've been playing around with some old hard drive motors recently, they seem to be of the synchronous reluctance type and are surprisingly difficult to drive (need the rotating magnetic field mentioned in the video). I guess that makes them good for accurate RPM control, like you need in a HDD...

author: David Hess
author_rank: Super Contributor
timestamp: March 10, 2021, 05:16:02 pm
content: Quote from: bdunham7 on March 08, 2021, 02:56:03 amBut did you compare them to proper 2 or 3 phase induction motors driven by an inverter? Permanent magnet motors have an advantage in power density but are they more efficient compared to an induction motor driven by an inverter?QuoteSwitched reluctance and permanent magnet motors have the disadvantage of higher cost and lower reliability compared to induction motors. The only reason either are an option now in lower cost applications is that the power electronics has become less expensive.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 10, 2021, 07:32:05 pm
content: An induction motor is cheaper and more reliable, when one does not need speed control or only crude 2 steps. However when one combines an induction motor and inverter things are more similar. There is a similar amount of electronics. The SRM can have advantages when it comes to speed control over a large range and may be a bit easier on EMI.Induction motor only work well for large size - they get increasingly lower efficiency below some 200 W. Especially the permanant magent motor can be scaled down better to small size. Not needing the create the rotor field be induction causes extra loss. So the loss from ohmic losses in the indcution motor is naturally something like 2 times higher.

author: bdunham7
author_rank: Super Contributor
timestamp: March 11, 2021, 03:42:33 am
content: Quote from: David Hess on March 10, 2021, 05:16:02 pmWell, the problem is there aren't any variable speed induction motor products to compare them directly to AFAIK. I've only rarely seen 3-phase induction motors less than 1 HP. The ones that I've had that were inverter driven were part of expensive machine tools and efficiency wasn't a concern. And the cost was astronomical at the time.The household products I'm talking about typically are introduced with government incentives and rebates for meeting certain efficiency requirements. If they could do it more cheaply and efficiently with induction motors, I would think that they would. The SRM and ECM-permanent magnet motors I have used, including my 6-year old car and 15-year old washing machine, have been 100% reliable so I can't really complain. Cost-wise, I did opt for a more efficient two-speed induction motor for my pool pump instead of the $1200 or so for the variable speed Pentair, but that is obviously not a direct comparison. There is no variable-speed induction version for me to choose from.The only direct comparison I can think of is in electric cars, there the SRM-type motors seem to have a slight edge in efficiency, but it's hard to separate the effects of the motor out from the rest of the car's systems. And if you add in an infinitely variable-speed design and regeneration requirement, I don't think induction motor systems are much more reliable or less expensive. Interestingly (at least to me), the AC compressor in the car appears to be a 3-phase induction motor--but that doesn't need to slow down to zero speed nor does it need to regenerate.

author: mzzj
author_rank: Super Contributor
timestamp: March 11, 2021, 05:45:44 am
content: Quote from: WattsThat on March 08, 2021, 01:48:10 amAFAIK switched reluctance motors are lot more difficult to tame than induction motor.https://www.motioncontroltips.com/faq-switched-reluctance-motors-srms-difficult-control/

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 12, 2021, 03:38:41 am
content: A friend of mine developed a very efficient (at the time) residential air conditioner that uses a switched reluctance motor for the compressor. It only took a few years for permanent magnet BLDC compressors to become even more efficient. A lot of those BLDCs are so called "hybrid reluctance motors" that work like a conventional BLDC motor at low torque and like a switched reluctance motor at high torque.The biggest efficiency improvement for HVAC is to focus the heating or cooling to where it's needed, using infrared sensors to detect where people are and then moving guide vanes in the vents to direct the airflow. Not much to do with the motors other than they will spend most of the time operating at low power levels, where BLDC does substantially better than both induction and switched reluctance motors. BLDC doesn't use current to generate the rotor flux and hybrid reluctance BLDC does even better at low torque because the permanent magnets only provide a fraction of the full torque flux, reducing iron losses.