Can externally spinning a motor damage a VESC controller?

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1

Hi everyone,

I have a question about spinning a motor externally while it is connected to a VESC.

My setup:

  • VESC 4.12

  • 10S battery pack (~36–42V)

  • BLDC motor 40KV, 80mm diameter (hub motor)

  • The motor is mechanically coupled to a 500mm diameter wheel

Scenario 1

The VESC is connected to the motor but not connected to the battery.

If I spin the wheel very fast externally, the motor also spins. When I measure between the motor phases with a multimeter, I can see around 70V AC between phases.

My questions:

  • Could this generated voltage damage the VESC even though there is no battery connected?

  • Where would that generated energy go inside the VESC in this situation (MOSFET body diodes, capacitors, etc.)?

Scenario 2

Now assume the VESC is connected to the 10S battery, but the VESC is just idle (not driving the motor, no throttle).

If the wheel is spun very fast externally and the motor generates high voltage:

  • Could this cause DC bus overvoltage on the VESC?

  • Could the VESC or MOSFETs be damaged if the generated voltage exceeds the battery voltage?

Because with this setup (40KV motor + large 500mm wheel), spinning the wheel fast enough can generate about 70V between phases, which is much higher than the battery voltage.

Has anyone experienced something similar?

Thanks!

2

I think that would kill the VESC. You have some headroom because I think those use 60v mosfets but try not to exceed that.

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3

Those spikes are bc it’s not connected to the battery. With the battery the spikes will be way less.

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