[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?

[jjsylvestre]

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.

[brandmeyer]

I dunno man, there is no silver bullet for high dV/dt, and SiC are harsher than most. Low-permeability core material and high switching frequency can help keep an LC filter compact.

[mliben]

To add to what Jason said-

The characteristic current of the machine is roughly the same as the maximum inverter current, so at maximum power the power factor is between 0.7-0.8. This also means the flux weakening capability (CPSR) of the machine is very good, although that isn't particularly useful in these propeller-load applications. In many applications the machine would spend most of the time at ~0.6pu speed and ~0.5pu torque (cruise), where the power factor is > 0.9.

I can't discuss the specific rotor design, but I will say it is a very high flux machine.