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Launch HN: H3X (YC W21) – High power density electric aircraft motors

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Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#81

Post by brandmeyer »

Uh, some motor controls questions...

What per-unit impedance are you targeting for the stator winding?

Does the motor controller need an LC output filter to keep the motor's high-frequency current reasonable (thus forming an LCL with the stator winding), or is the stator winding inductance sufficient on its own?

What techniques did you employ to get a wide speed range? Is it an interior permanent magnet machine, surface-mount permanent magnet machine, etc...

Does the controller have a common-mode filter of any sort to cut down on the common-mode bearing current?

Are you building off of 1200V SiC 'FETs or 1700V?

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#82

Post by emaciolek »

ed_balls wrote: post #79

Is anyone working on a hybrid system? I'd imagine having extra electric motors would help with taxi manoeuvrability, give extra boost from takeoff and could save fuel while cruising.

Yes there is a lot of development being done in the hybrid space as energy storage solutions aren't quite good enough for the longer range flights currently. One example is a VerdeGo Aero. Hybridization is also a good transition technology to all electric solutions as the electric infrastructure continues to grow.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#84

Post by jjsylvestre »

brandmeyer wrote: post #81

Uh, some motor controls questions... What per-unit impedance are you targeting for the stator winding? Does the motor controller need an LC output filter to keep the motor's high-frequency current reasonable (thus forming an LCL with the stator winding), or is the stator winding inductance sufficient on its own? What techniques did you employ to get a wide speed range? Is it an interior permanent magnet machine, surf…

I'll let @mliben comment on the motor questions.

The motor inductance is relatively low so we're running a high switching frequency (40-60kHz) to maintain reasonable phase current ripple. No output filter is used. Also, our phase busbars are very short so we don't run into the transmission line effects you typically see with fast switching SiC/GaN and phase cables.

We are looking into some advanced modulation schemes and switching topologies to reduce CM bearing current. Also looking into hybrid bearings with ceramic balls. This is definitely an area of active research, but we are trying to get away from a CM input filter as they can be bulky and heavy.

Right now, we are using 1200V SiC MOSFETs.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#85

Post by LeifCarrotson »

mliben wrote: post #77
baybal2 wrote: post #69

Earlier quoted context omitted.

Silver is heavier than copper. That's why people were so upset when carbon nanotube yarns happened to be poor conductors. People were thinking of super light motor windings.

Aluminum has the best conductivity/mass out of all of the common conductors. Motors are actually more volume constrained than mass constrained for the windings, which is why copper is typically used there instead.

Copper is also 60% better in the thermal conductivity properties as well, which is another critical property.

Power density in an electric motor is really based on how fast you can remove heat from the motor. I'm involved in sizing industrial servomotors, but even there you have 1s/10s/60s power ratings.

I wonder if H3X can post higher power levels for takeoff, assuming it starts cold and the flight plan calls for throttling back after a certain altitude is reached. And even in the event of an immediate 150% power return to runway after a 150% takeoff, the motor might only have slightly degraded the winding insulation; it can almost certainly exceed its ratings once for long enough to get back to the ground.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#88

Post by jjsylvestre »

jjsylvestre wrote: post #86
starpilot wrote: post #83

Do you think a supersonic, VTOL electric aircraft is theoretically feasible?

Paging Elon..

Theoretically, yes I think so. There are some key enabling technologies (energy storage and electric propulsion) that need to be developed further before something like that could be built.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#89

Post by cjbprime »

elihu wrote: post #65
mercurywells wrote: post #8

Earlier quoted context omitted.

> One aircraft we looked at required 30-35MW during takeoff and ~10MW during cruise. Do you envision some airframes to include assisted take-off technology? (JATO and the like, even catapults)

A simpler alternative could be to just have an electrified runway. The plane draws power from power rails embedded in a runway, or something like that. So, it doesn't switch to batteries until it's in the air. You could even have a long cable that hangs behind the plane and keeps an electrical connection until you're a few hundred feet up. (I'm picturing it connected to something like a slot-car that travels in an el…

Or for an even simpler alternative, just get towed into the air as motorgliders are (the ones with sustaining motors but not auto-takeoff).

I wonder if this tech might be better suited to self-launching motorgliders than GA.

Re: Launch HN: H3X (YC W21) – High power density electric aircraft motors

#90

Post by Retric »

mliben wrote: post #59
serjester wrote: post #32

Earlier quoted context omitted.

Keep in mind that an electric motor isn’t limited by the amount of oxygen in the air. As a result it can fly significantly higher where there is far less air resistance. Since air density is proportional to the square of the elevation this can lead to significant efficiency gains. Believe it or not, partly as a result of this, the SR-71 had it’s best mpg at peak speeds.

A simple physics-based plane model (like the one we made to understand vehicle-level impact of our technology development) dictates that the range-optimal cruise speed is proportional to 1/sqrt(air density), so it makes sense that the blackbird was more efficient at high speed when at high altitudes (admittedly, this simple model is subsonic, and there are a lot of other factors for supersonic flight). Since having l…

Unless I am missing something obvious, lift-induced drag is largely independent of altitude. However, parasitic drag is significantly reduced by lower air pressure. Thus the advantage from high altitude flight.
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