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An article on power to weight ratio in switched electronic motor control design.

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floobydust:
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 Technologies is 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.

NiHaoMike:
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.

Zero999:
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/

rob77:

--- Quote from: NiHaoMike on June 14, 2022, 11:03:06 pm ---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.

--- End quote ---

i'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.

NiHaoMike:

--- Quote from: rob77 on June 15, 2022, 04:17:41 pm ---i'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.

--- End quote ---
If 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.

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