Attempting to apply rkfixed to a PMSM motor

[ptc-6822891]

Getting huge phase currents. The equations on the right for tt and vv are from a worked out problem from the internet the results there look ok.

So I think I have the correct format for the motor currents.

Could someone check me out?

[StuartBruff]

Could you provide a link to the internet problem, please?

Thanks,

Stuart

[ptc-6822891]

Stuart,

Thanks for looking at the problem! I can't find a hard copy or soft copy on my computer of the problem from the source. I just kept it in the PMSM currents and torques vs time.mcd file. My motor current problem is on the left and the example is on the right side.

Regards,

Chuck

[RichardJ]

Do you mean B(tt,y) is the example? It's a different equation, with different scaling factors, over a different time frame.

[ptc-6822891]

Yes, I used the B(tt,y) as the example. I just tried to follow that format.

[RichardJ]

I see. As far as I can tell, your worksheet is correct.

[Fred_Kohlhepp]

If we put units to it, we get a significantly larger current.

Where are we solving for torque? Don't you change current if you load the motor?

[RichardJ]

van (or VAN) should be 260*0.3V. At least, I assume that is the correct number and it's not a typo.

[ptc-6822891]

oops

VAN = Vrms phase A to neutral = 460 VrmsLL/1.732 = 265.6

I meant to use 260 V

[RichardJ]

OK

Aside from that, I still don't see anything wrong with the worksheet though.

[Fred_Kohlhepp]

Thank you--long day, bad eyes!

With that correction the solutions collapse.

But we still don't have torque and load weighing in.

[ptc-6822891]

Ke = 81.7 V/krpm measured

or

Ke = 81.7*60/(1000*2*pi) = 0.78 V/rad/sec

Kt = (3/2)^.5 * Ke = (3/2)^.5 *.78 = 0.955 Nm/Apk

or

Kt = (0.955 Nm/pk)*1.414 = 1.35 Nm/Arms

The the internal setting of our Voltech power analyzer measurements was incorrect. So now the voltage and current measurements are in question.

Plan to retest in a few weeks.