ODrive Trip Levels and Regen Clamp

Support ODrive Pro Support
1

Hi,

I’m trying to configure a system where we have an ODrive Regen Clamp between a 48V, 50A DC power supply and an ODrive Pro driving a D6374 150KV motor.

I don’t quite understand how the regen clamp impacts the values we should set for dc_bus_overvoltage_trip_level, dc_max_positive_current, and dc_max_negative_current.

I’ve tried setting:

  • dc_bus_overvoltage_trip_level to 48V (rating of the DC power supply)
  • dc_max_positive_current to 50A (rating of the DC power supply)
  • dc_max_negative_current to the 10mA default.

However, when we do position control we get a DC_BUS_OVER_VOLTAGE error anytime we try to change the velocity limit above the default 10 turns/s (even a change to 11 turns/s causes us to get the error).

Should we be using different settings for the trips given that we have a regen clamp connected? (E.g. should the dc_max_negative_current be set to the maximum regen current calculated when sizing the brake resistor?). Or is it likely that there’s something else wrong in the config/system that’s causing this?

2

Hi! A few things:

  1. The Regen Clamp clamps the voltage at about 2.5V above the bus voltage, so you’d need a minimum overvoltage trip level of 50.5V, though it’s always good to have some headroom here due to voltage drop in the wires, transients, etc – so I’d maybe do 52V.
  2. Since the Regen Clamp allows for regenerated current on the bus, dc_max_negative_current should theoretically be set to the maximum current the Regen Clamp can dissipate. Assuming you’re using the default 2 ohm resistor, that’s 48V/2ohm = 24A, so this should be set to -24.

Note though that both the ODrive Pro and Regen Clamp are happy up to 58V, and sometimes you may have very brief regenerated current transients that are higher than 24A that you don’t want the ODrive to trip on, so you could set the Pro overvoltage trip limit to e.g. 54V and dc_max_negative_current to some high value like -50A, which would let the bus voltage float up a bit with large regenerated transients, but give it some headroom before throwing an overvoltage trip.