cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Showing results for 
Search instead for 
Did you mean: 

Community Tip - You can Bookmark boards, posts or articles that you'd like to access again easily! X

Attempting to apply rkfixed to a PMSM motor

ptc-6822891
1-Visitor

Attempting to apply rkfixed to a PMSM motor

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?

11 REPLIES 11
StuartBruff
23-Emerald III
(To:ptc-6822891)

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

Thanks,

Stuart

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
19-Tanzanite
(To:ptc-6822891)

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

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

RichardJ
19-Tanzanite
(To:ptc-6822891)

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

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?

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

oops

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

I meant to use 260 V

RichardJ
19-Tanzanite
(To:ptc-6822891)

OK

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

Thank you--long day, bad eyes!

With that correction the solutions collapse.

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

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.

Announcements

Top Tags