ODrive Speed Limits

Afternoon all,

Quick question.

Is the ODrive able to run an escooter motor at its rated speed?

For example I’m planning on swapping the motor controller from my existing scooter to an ODrive and want to be sure I’ll be able to match the current performance.

I recall the docs somewhere mentioning it can only do up to 75% or rated speed. Is this still the case?

75% of bus voltage * motor Kv = max speed. So depends on the motor whether or not it hits max speed before that voltage limit.

Cheers, this is what I’d read previously.

So essentially, the Odrive is only capable of running a motor to 75% of its rated speed (at rated bus voltage)? Am I correct in saying this has something to do with how the ODrive is doing it’s current monitoring for the FOC loop?

Based on this, would the only way to run a motor at it’s rated speed be to have a bus voltage of 1/0.75=1.333 times the motors rated voltage?

Yes. With ODrive v3.x due to having only 2 current sensors, it needs some dead time to be able to sample the current sensors away from the PWM switching edges.
You can use a motor rated for 36V or 24V and run it at 48V happily though.
The voltage ratings on hobby motors are designed to protect them from mechanical overspeed, not overvoltage.

Even ‘bog standard’ enamel wire insulation is good for a few hundreds of volts. You can’t really over voltage a motor at 60V.

Ah interesting.

In theory, if the ODrive were to have 3 current sensors, would this solve this dead time issue?
Or would the PWM noise still cause issues?

Yes, ODrive V4 (to be released "Soon"tm) will have 3 shunts, so it will always be able to pick two phases which are not going to see a PWM edge within the ADC sampling window, so I understand.