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Need to design and build 250W BLDC inverters for drones

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We wish to build drones capable of carrying up to say 5kG. Therefore  we need  four  3 phase BLDC inverters capable
of 250W each.
We must build the inverters ourselves, and not import them in from outside Europe/UK/USA/Australia.
There are very few companys in EU/UK/USA/Australia that build drone inverters, so we need to do this ourselves.

Please offer us any help you can?

The inverter bit looks simple....just a bridge of four suitably heatsunk MOSFETs. [EDIT...Six as kindly pointed out below...ENDofEDIT]

Do you know of inverter control chips for this, or chipsets?
What battery voltage would be best would you think? (we believe 48V is best, with matched series/parallel cells and "stop_when_any_is_full_or_empty"
charging regime.)
they will have 4 propellers, so we need four 250W inverters.
So thats  6 Amps from each battery.

Do you think a microcotnroller would be best to provide the Inverter MOSFETs gate drive
So we need it to receive the four rotor position sensors, and then push out the drive signals
, and have the four speed inputs from the Autopilot.

Please help with this?

6 mosfets per motor surely? They are three phase machines.

Usual approach is gong to be a micro running the whole thing, possibly one of the various dual core offerings so you can have the small core doing the really hard realtime motor control stuff and the bigger one handling flight dynamics and related functions. Have a poke around the ST STM stuff IIRC they do some micros that have the numerous timers that are useful for producing gate drive signals for such things and I think there is example code for field oriented control out there in an app note, including code for sensorless operation which seems sane in this case (You don't likely need very low speed control, so why bother with the sensors?), some of the micros have ADCs and comparators useful for the motor drive stuff on chip.

Likely you can find a modest integrated three phase bridge and gate driver as a packaged part, maybe with integrated low side current sense, which will save significant area if you can find a suitable part, I would be eyeballing Infineon's offerings, maybe also TI.

There are standalone motor controller chips, but you are going to have a micro anyway, might as well save on 4 chips and just do it in software.

48V is good, but it is going to be a question of what fets best suit your purposes, also what works for battery form factor, these is sometimes something to be said for designing to use standard power tool batteries!
Don't forget you need to keep the hash out of the radio & gps subsytems as well as anything like analogue video links, so EMC is a first class consideration in design, as annoyingly is weight which directly comes of your cargo capacity and duration.
On that subject, bigger props are almost by definition better then smaller ones (As long as the tips stay subsonic!) simply because momentum is mv, but energy is mv^2, more air slower is less energy cost then less air faster. 

It is a nice little toy project, and can grow to arbitrarily complex as it grows sensors, failsafes and extra telemetry, should be fun.

There is plenty of open source work in this space, and I am sure you will find both BLDC drive and full up drone hardware and software on github, none of this is magic.

In your other post you said "we Can" build the entire drone. In this post you saying "we Wish" to build a drone. I feel this is one of the "I am building a gizmo X but have no idea where to start" type of post.


--- Quote from: Bud on February 28, 2024, 05:08:09 pm ---In your other post you said "we Can" build the entire drone. In this post you saying "we Wish" to build a drone. I feel this is one of the "I am building a gizmo X but have no idea where to start" type of post.

--- End quote ---

as usual ... and probably made up as an excuse to complain about Chinese electronics

FTTS: usual clickbait post

  drone motor inverters are  easily found at  RC plane or drone parts 

  V in 12/24/48V 
from China or Japan



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