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Maximum Torque

Javier Vara
Expert 1645 points

Hello,

We are using SpinTAC sensored to run a very high torque motor (450Nm). The variable gMotorVars.Torque_Nm is an _iq24 variable which means that the maximum value it can hold is +-128, right? and therefore it will overflow. If that is the case, what changes should I make to get a good Torque estimation?

Regards

Javier

  • 0
    Guru 12800 points

    Javier,

    There have been quite a few posts about this on the forum previously.  Try taking a look at the one I've linked below.

    This one is specifically talking about current, but you should be able to apply the same principals to the torque.

  • 0 in reply to Adam D. Reynolds
    Expert 1645 points

    Adam, 

    I have seen those posts. The motor I am running is a high current one (600A) so I have already made all those changes so that I can run the motor. I just wasn't sure about the proper changes for the torque. Since gMotorVars.Torque_Nm is calculated in the function USER_computeTorque_Nm I was wondering if I should change the gTorque_Flux_Iq_pu_to_Nm_sf and the gTorque_Ls_Id_Iq_pu_to_Nm_sf scale factors (dividing by 10 for example) to avoid the overflow and whether or not I had to make any extra changes that I am not aware of.

    Regards

  • 0 in reply to Javier Vara
    Expert 1645 points
    Actually, I have just looked up how those scale factors are calculated and it is likely that they would also had overflown right? In that case if I substitute USER_IQ_FULL_SCALE_CURRENT_A by USER_IQ_FULL_SCALE_CURRENT_A/1000.0, in what units would the torque be calculated? kNm?
  • 0 in reply to Javier Vara
    Guru 12800 points
    Javier,

    I think your approach is the right one. I don't believe that the torque in Nm is used for control and so I don't think it would impact any of the inner workings.
  • 0 in reply to Adam D. Reynolds
    Expert 1645 points

    ok. I have been playing with it for a while and I think I got it. It doesn't work to substitute USER_IQ_FULL_SCALE_CURRENT_A by USER_IQ_FULL_SCALE_CURRENT_A/1000.0 because one of the scale factors do not scale linearly with current so what I did was to divide the scale factors by 1000.0 before they are converted to IQ since they are calculated in float and I think that will work.

    Thanks for your help