Can Myxa be damaged by self-spinning motor

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1

Hi all,
I have a motor connected to Myxa.
While the Myxa receives 0 command (i.e. motor is stationary) I want to spin the motor through other means.

  1. Will the Myxa try to forcefully stop the motor to comply with the received command? If the answer is yes - can this feature be turned off?
  2. Can this procedure damage the Myxa in any way?

Thanks!
Gad

2

Hi Gad,

  1. Yes, if the ctl.hard_stop parameter is set to false. Just set it to enable to enable the freewhiling stop.
  2. Yes, if the deceleration ramp is too high especially at the battery voltage value close to Myxa’s maximum dc bus voltage. The bulk capacitor is not able to absorb so large power surges. This leads to voltage spike on the Myxa and can damage it. Decrease the deceleration ramp, or attach the additional bulk capacitor with very low ESR, or enable the freewhiling stop.
3

Thanks Dmitry.
Just to clarify - what I’m trying to achieve is that when the vehicle is UNARMED I’ll be able to spin the motors attached to the Myxas by an external means without damaging them.
The spinning will be stopped before the vehicle is armed.

I wanted to ask is whether the above procedure can be potentially harmful to the attached Myxas and what is the correct setup for it and its safe working boundaries.

Hope this makes it clearer…
Thanks!

4

Hi Gad,

If you spin the motor attached to the ESC, the motor works like a generator producing the EMF on the phase connectors of the ESC. If the EMF is lower than max ESC voltage (56V for Myxa ESC), the spinning won’t be potential harmful to the attached ESCs.

5

So if I have a 240Kv motor, assuming ctl.hard_stop=false, it can be spun up to 240*56=13440RPM without damaging the ESC.
Is this correct?

6

Yes, but I would recommend to have some voltage reserve, at least 5 volts, i.e. substitute 51 V instead of 56 V in calculations.
And if you want to freewheel the motor during stop, you should set ctl.hard_stop to true.