Limited power application

Hi all, I’m trying to alter the Odrive to work from an ATEX verified power supply. This means that the current will be very much limited. I want to implement this by connecting this power supply to only the inverter. The rest of the ODrive will still be powered from a ‘regular’ power supply. I increased the resistance of the shunt resistors to increase accuracy. Does anyone see any problems in altering the ODrive in such a way. I would imagine that the voltage will drop quite a bit, especially at startup, will this be a problem?

The motor powered can be a very small motor. Is there anyone who can say anything about whether a BLDC motor will even start spinning from such a limited supply, since the inrush current will also be very much limited?

I added a schematic to give a bit more clarification about the modifications made.

Obviously you need to account for the resistance change in the firmware.

But please be aware, ODrive is NOT certified for use in explosive environments by any stretch, even if you power it from an ATEX certified power supply.
The capacitors on board for example store plenty enough energy to make a spark, and remember that the motor that you are driving is an inductor, which also has the ability to store energy and step up voltage depending on the switching speed…

For it to be ATEX compliant, the whole system would need to be designed to the regulations, not just the power source.

Yes the resistance should be changed in the firmware but this shouldn’t be too difficult.

Regarding the ATEX certification: the whole inverter will be galvanically isolated from the driver, to make it safe. This is also the reason why I’m considering using P-channel MOSFETs for the high-side switches. Other than inverting the control signal, would this give rise to any problems I’m not considering?

I’m also still wondering whether the power available would be enough to let the motor spin, hope someone can give me some insights into this.

The 16.9 Ohm resistor at the top is obviously going to cause problems. ODrive’s control algorithm needs to assume that the top of the bridge is at the DC Bus potential. But with that resistor, it will wobble about all over the place.
What is the winding resistance of your motor?

I can’t see how isolating the mosfet bridge from the rest of ODrive makes it safe tbh. If you have enough energy to spin a motor then you have enough energy to make a spark. Also, don’t forget that PWM inverter drives are a kind of SMPS - the current in the windings is always higher than the current drawn from the DC Bus, due to the recirculation during the ‘off’ cycle.