An article on power to weight ratio in switched electronic motor control design. - Page 1
Forum section: electronics / general

author: Peter Taylor
author_rank: Regular Contributor
timestamp: June 14, 2022, 06:04:51 pm
content: This article explains why the Delta and Star configurations have one third less power to weight ratio than an Open configuration in switched electronic motor control design.Definitions:Power to weight ratio is the amount of power produced in one revolution of the rotor compared to the weight of copper wire in the stator windings.Diagram 1 shows a Delta configuration, and the truth table shows the eight ways the three windings can be driven. A one for connection A and a one for connection B means that A and B are at the same voltage level and there is no voltage across stator winding AB (as highlighted).This means that one of three windings is never utilized in producing power in a revolution, giving 2/3 of the maximum power to weight ratio.Diagram 2 shows an Open configuration, and the truth table shows that there are sixty four ways to drive the windings, and all windings can be made to produce power in one revolution, giving a maximum power to weight ratio.QED

author: langwadt
author_rank: Super Contributor
timestamp: June 14, 2022, 06:18:52 pm
content: what it shows is that you don't understand how three-phase motors work ....

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2022, 06:19:10 pm
content: not again !Quote from: Peter Taylor on June 14, 2022, 06:04:51 pmplease elaborate on the "all windings can be made to produce power in one revolution" ...

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2022, 06:22:04 pm
content: Quote from: langwadt on June 14, 2022, 06:18:52 pmhe already had a thread with this crap the other dayand yes he's totally lost and has absolutely no clue how 3phases work.

author: Miyuki
author_rank: Frequent Contributor
timestamp: June 14, 2022, 06:29:33 pm
content: Of course, the third winding is just laying around because all engineers for 150 years were totally dumbAnd if you add three more windings you can even create more energy than the motor consumes and turn it into a magical free energy device, or maybe attach it to a carpet to build a flying carpet

author: rob77
author_rank: Super Contributor
timestamp: June 14, 2022, 06:42:25 pm
content: Quote from: Miyuki on June 14, 2022, 06:29:33 pmyes every extra 3 windings will add one more unit of free energywe need to quickly share this because "They" don't want us to know this , and "They" will delete all the related information from the internet soon

author: Benta
author_rank: Super Contributor
timestamp: June 14, 2022, 07:54:55 pm
content: "This article explains why the Delta and Star configurations have one third less power to weight ratio than an Open configuration in switched electronic motor control design."Which article? I only see some scribbles.This from someone that apparently has understood less than 3% of the subject (Electrical Motors), but feels intitled to make "statements".The last thread was bad enought, but this one is over the hill...

author: Gregg
author_rank: Super Contributor
timestamp: June 14, 2022, 08:00:28 pm
content: WTF; is PeterTaylorTroll trying to describe a rotary data processor?? Pure evil genius soon coming to a go fund me.So by putting 3 phase power/data in to the mystical super motor and retrieving processed data and power out via extra windings (in accordance with the truth tables, of course) this magical device will somehow not only process the data but it will be more efficient than conventional 3 phase induction motors. In other words, a true digital motor.BUT: I think the OP is missing the boat with his unconventional thinking. Why is this miracle being described in a binary logic, when it could be 50% more powerful with a trinary input/output? Is this obvious improvement also being suppressed?Back to reality…Sorry, I let my imagination run amok…maybe faulty thinking is contagious.

author: eugene
author_rank: Frequent Contributor
timestamp: June 14, 2022, 08:06:44 pm
content: Quote from: Peter Taylor on June 14, 2022, 06:04:51 pmBy "article" do you mean "forum post"? Why not just call it a "published paper"?In any case, if you claim to have solved a problem then you first need to show that the problem exists.First, give us a real example of a real 3 phase motor that is wired in either delta or star configuration and is driven by switching DC voltages in the way that you describe.Then show us how the same motor could be driven using all three windings at the same time, still switching DC voltages.

author: Benta
author_rank: Super Contributor
timestamp: June 14, 2022, 08:22:18 pm
content: Here's the "article" background:

author: floobydust
author_rank: Super Contributor
timestamp: June 14, 2022, 10:23:21 pm
content: Don't laugh, there's many nutbar electric motor ideas out there, some have acquired millions of dollars of investor funding. Of course they are clueless about physics, magnetism etc. but the hype gets buy in.Exro Technologiesis one example, look at the funny patents from a guy whose background is in "food science" lol.No real product, "Coil Driver" technology appears to be tapped coils. But it has maximum marketing hype. It's all based on small generators needlessly running at synchronous speed at light loads, and the "inventor" thought he might stop the waste. It's just silly tech being exploited.OP obviously hasn't heard of aluminum wire, which would cause his head to explode- because his "power to weight ratio" is a fantasy, bullshit metric. Who cares how much the windings weigh when you've got steel laminations and magnets that weigh much more. DUH.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 14, 2022, 11:03:06 pm
content: Actually, wiring the 3 windings of a 3 phase motor to 3 separate single phase power stages theoretically gives an improvement over having the windings in either Y or delta to a 3 phase power stage. The reason being that while the two phases of 3 phase are 120 degrees apart, the opposite outputs of a single phase inverter are 180 degrees apart. Thus the maximum AC voltage for a given DC voltage is a little higher.I haven't seen any real world use of that, I guess the increase in complexity cancels out the benefits.

author: Zero999
author_rank: Super Contributor
timestamp: June 15, 2022, 09:42:36 am
content: Why post the same crap again and expect a different result?https://www.eevblog.com/forum/chat/star-and-delta-motor-field-winding-configurations-are-not-efficient/

author: rob77
author_rank: Super Contributor
timestamp: June 15, 2022, 04:17:41 pm
content: Quote from: NiHaoMike on June 14, 2022, 11:03:06 pmi'm afraid i'm not following you there.... so how exactly the waveforms would look like and how would the rotating magnetic field look like ? isn't 180 degrees apart a single phase ? there is a 1:1 relation between waveforms and mechanical construction of an electric motor.. if the motor is constructed for 3 phases 120 degree apart then that's the only way how to feed it.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 16, 2022, 02:03:43 am
content: Quote from: rob77 on June 15, 2022, 04:17:41 pmIf you have the motor wired in delta, the inverter gives it 3 phases 120 degrees apart. If you have a 340V DC bus, the biggest undistorted sine wave you can get between two phases is 208V.If you have the motor wired with each winding to 3 separate single phase inverters, a 340V DC bus would get you a 240V undistorted sine wave between the ends of a winding. The 3 inverters are run 120 degrees apart so the phase relation between any two windings is still 120 degrees as was the case with the 3 phase inverter.Another way of looking at it is to take a delta wired motor and inverter and double up on the inverter phases. Then split the connections so that the three windings each gets its own pair of inverter phases. The breakthrough is that the phases supplying a winding no longer need to be 120 degrees apart to maintain the correct phase relationship with the other 2 windings and can instead be 180 degrees apart, giving more voltage.

author: Circlotron
author_rank: Super Contributor
timestamp: June 16, 2022, 03:03:40 am
content: Quote from: Zero999 on June 15, 2022, 09:42:36 amIn that post I can see what the author is saying. Not that I necessarily buy it though.Get a 3-phase 6-switch inverter so that each leg is either high or low, no dead time. With reference to the halfway point of the DC buss each output will be a square wave. Now get your scope with differential probes and measure across each winding of a delta connected motor. The winding voltage will be 2/3 high, 1/3 off, 2/3 low, 1/3 off, repeating. Now if we separate the windings so that all six ends are available and connect each winding to it's own individual H-bridge so that we now have 12 switching devices instead of 6 it will be possible to drive each winding with a proper square wave with 100% on time instead of 2/3 on time. That's the guts of the argument as I understand it. How the motor would behave with a square wave to each winding instead a 2/3 wave (which is in fact closer to a sine wave than the pure square wave) I don't know.With the foregoing there might be some difference in motor behavior if each H-bridge produced a pure square wave. If though they each produce sinewaves there would be no difference to a 6-switch inverter.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 16, 2022, 03:25:51 am
content: Quote from: Circlotron on June 16, 2022, 03:03:40 amAs mentioned, with the sine waves 180 degrees apart instead of 120 degrees, you get about 15% more voltage for the same DC voltage.

author: Circlotron
author_rank: Super Contributor
timestamp: June 16, 2022, 04:32:07 am
content: Quote from: NiHaoMike on June 16, 2022, 03:25:51 amSo with opposite legs of each H-bridge producing sine waves 180 deg apart, and the resultant sine waveacross the motor windingbeing 120 deg or 240 deg from the other windings.

author: andy3055
author_rank: Super Contributor
timestamp: June 16, 2022, 04:47:17 am
content: There are people who come up with stupid ideas, post them in public forums and sit back, relax and laugh at all who are contributing and arguing about what he/she has written. Not to mention arguing with each other! Why does he not have any come backs to what is being said?

author: Miyuki
author_rank: Frequent Contributor
timestamp: June 16, 2022, 07:22:03 am
content: Quote from: NiHaoMike on June 16, 2022, 02:03:43 amOnly if you use simple modulation, when you add this order sine, you can get full 240V in a simple 3 wire configurationThis is already solved and usedYou can reinvent the wheel but it will end up always the sameAlso, there is a reason why motors use 3 phases in symmetrical spacing (some can use more phases like stepper motor commonly have 4)Two phase/ 180 degree motor won't ever run smooth and efficient

author: langwadt
author_rank: Super Contributor
timestamp: June 16, 2022, 09:38:57 am
content: Common steppers are two phase 90 degree. 180 is not two phase