Field Weakening of SM PMSM : An Experimental Approach
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- Опубліковано 14 жов 2024
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References
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Notes1: Keep in mind that it is quite difficult to differentiate between the contribution of Lambda_m and Omega_r*Ld*Id contributions to torque as increasing Id causes Ld to change and hence a reluctance torque is added. Even measuring Vq does not conclusively prove Lambda_m doesnt change.
Hello, greatly appreciate your work and these videos regarding PMSMs and FOC. One question; you mentioned position sensor should be properly calibrated and and delays should be compensated before going into field weakening. What sorts of delays should we care in this case.? Thanks in advance.
Hi Gayan, computational delay and inductive lag may introduce some severe offset at high speed. So those should be compensated by advancing the angle.
@@SandunKuruppu Thank you for your quick reply. Ok, I see. Is this a typical issue when implementing FOC on PMSMs. What are the methods of determining angle offset error caused by delays. And how can we mathematically advance the angle in the algorithm in real time.?
@@gayanniroshana7630 The misalignment caused by delay can be determined in several different ways. Easiest is to run the motor at the speeds you want and measure applied Vq, Vd pair and compare that to a model based value to determine what the error is. This paper will help find this. ieeexplore.ieee.org/abstract/document/9449553. To compensate, you can use a speed based position correction lookup table and at each speed instance, update the positions signal used. This also can be in other ways.
@@SandunKuruppu Thank you for detailed explanation and the reference. This answered my doubts very well and would certainly be helpful for my work.
Here's something from my recent experience on field weakening. I'm testing a SM PMSM with FOC implemented. The basic FOC controller was tuned well so that the motor runs without any issues. The position sensor is a resolver and we use a system on chip solution for reading the resolver. I implemented field weakening and was able to increase the motor speed to a decent level. The issue that I have is when recovering from field weakening region a reverse DC bus current tends to appear during the recovery time. The motor is connected to an external load with low friction to provide an adequate amount of inertia to the motor setup.
What would be the reason for this ?
Hi thank you for the video! Would appreciate if you can also talk about demagnetization in PMSM
Hopefully soon!
Hello Sir, thank for informative video. Can you please tell me if Ld and Lq values remains constant for all speed range ( 0 to base speed & base speed to max speed)? Thanks in advance
Hi Parth, Ld and Lq are inductances. Theoretically they do not change with speed unless the magnetic saturation level of the machines changes. Now, practically you will have to verify if this changes based on the saturation level.
How could the back EMF of PMSM obtained..during normal operation and field weakening??
Pavan, please check out my other playlist linked below for the details.
ua-cam.com/video/dA5BtNf2BDk/v-deo.html
In an hall sensor based Ipmsm machine while doing reverse motoring , I made Iq negative . And for flux weakening i made id negative . I observed a reduction in speed rather than increase . Can u help me to understand why the speed is reducing even though we are applying negative id current. Is it because of saturation
Hi Debasis, I will need some more information before I answer. Do you have field oriented control implemented? Are you testing on a dyno, where the motor speed is regulated by another machine? When you regulate current, you are controlling torque. Was the position sensor properly calibrated? How did you verify if it was properly calibrated?
Hi Sandun,
Thanks for quick response. It was an IPMSM motor in my case & field oriented control is implemented. Basically it is for an EV 2 wheeler application and the throttle is mapped to speed( say 0-100% thrrotle corresponds to 0-700 rpm). I have set the field weakening threshold speed below rated speed to simulate the field weakening . The position sensor is properly calibrated ,I have matched the hall sensor with the back emf . And in my case I have implemented both speed and torque control. I hope I have addressed all your questions.
@@jubul1988 How are you testing the motor? Does it have a load or is it free running? Can you share a video of what is happening? You can send me a private email if you dont want to share publicly.
Also, why are you using field weakening below the rated speed? You will end up running with lower efficiency.
@@SandunKuruppu we are testing in free running and sorry for the mistake we are doing field weakening above the rated speed not below rated speed . I ll try to capture and share a video by mail.