LAUNCHXL-F28379D: Torque pu to Nm conversion

Hi,

The expert is out of the office because of Holiday. Please expect a reply by Tuesday.

Thanks.

Do you want to calculate the output torque of the running motor? Or just to convert the rated torque of the motor to the value with N.m in the datasheet?

The torque calculation formula you used seems like correct, but the flux calculation is not correct.

Hi Yanming,

I want to convert the Iq value  which is in pu (which is got from the speed reference in the below image), to get the equivalent torque in Nm.

For example in Build level 3 of the dual axis code ,if we set motorVars[0].IqRef to any value, how much actual torque does that translate to in Nm?
If we connect a torque meter on the motor shaft, we should be able to match the theoretically calculated torque (from motorVars[0].IqRef) to the value that the torque meter shows me.

You mentioned the Flux formula is incorrect, could you give me the correct equations.

Thanks!

Yes, you need to convert all of the variable with PU format to the SI format to calculate the torque.

You need to convert the Vpeak/kRPM to Wb for Flux, the equation could be Wb = (Vpeak/kRPM) * 60 / 1000 / sqrt(3) / (pole pairs). You can have a try to verify if it's right.

Hi Yanming, Thanks for the formula,

Now I am thinking the torque is a little on the higher side 

So for 0.99 pu Iq current, does it translate to a torque of 4.4 Nm?

Arun Kumar said:

So for 0.99 pu Iq current, does it translate to a torque of 4.4 Nm?

Not right. You need to multiply the base current to convert the PU to SI value.

Hi Yanming, I did multiply the base current?

Torque(Nm) = 3/2 * Pole_Pairs * FluxPM * (Iq * Iq base value)