Why is sinusoidal current best in a DC motor?? (Episode 9)
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- Опубліковано 9 жов 2024
- This week we develop a new and better plan for the current we will send through our BLDC motors! like, comment, and share, but only if you want to. I will be taking a week off next week to try and get a little bit of a head start on the next couple of episodes.
Is it weird that I'm excited for Thursdays now? Clear, concise, and informative. Keep em coming! 👍
Thanks so much! Due to a crazy week at my full time work, I am a little behind on my production schedule so there most likely won’t be a new video next week, but by week after next I will for sure have a new episode finally getting into field oriented control!
@@jtlee1108 No worries at all, take your time! Just know they're definitely appreciated whenever they're ready.
I truly appreciate your extraordinary work in teaching us these principles seamlessly. Your dedication to delivering complex concepts in such a clear and approachable manner is truly invaluable. Thank you for making learning such a challenging topic so enjoyable and understandable
As a firmware engineer who is working on design FOC for a motor, I really enjoy watching your vids while working. It makes feel confident that problems can be solved in no time.
These videos are absolutely amazing, keep it up!
Thank you for excellent videos!
amazing video! goodexplanation, much appreciated
Holy shit man these videos are soooo gold. I need more. I'm part of a really huge project and you've really improved my understanding of motors, thank you, keep it coming
J. O. Very glad you enjoy it! Hope I continue to live up to it
@@jtlee1108 Btw, we have a deadline 2-3 weeks from now on deciding the concept. In that time, I must finish my reading up on the material, before going to design, which must be finished 1.5 months from now (I'm working on the inverter and control system).
Can you give me a few pointers on what your remaining videos will be about, so I can research it further and perhaps pitch a few of them to the group?
@@j.o.5957 yeah id be happy to. But I want to clarify up front that while I 100% hope this is helpful for anyone, it is primarily meant as a bit of a crash course for people who, like me, went a mechanical engr (or similar) route, but end up working with motors and want to understand them intuitively. I cant guarantee my notations or ways of describing things will be consistent with electrical engineering courses or anything like that. But that said, as it is outlined now, episode 11, which should come out tomorrow, is talking about performing (alternating reverse) SVM in a more practical sense (IE what do you actually send to your mosfets and such). episode 12 is set to cover motor data sheets, what the important values mean, and how to get an idea of what you need. episode 13 is currently set to be regeneration, episode 14 is set to talk about motors with multiple pole pairs and how that effects construction, hall sensor placement, and general control. then finally episode 15 is set to be the control theory side of making nested controllers for motor control, and how to optimally tune your current controller. the last 3 may change in order, and right now my actual job is busy, so they may be released every other week instead of weekly, as I had been doing. any who, cheers, and best of luck with everything
@@jtlee1108 Thanks man, really appreciate the effort you're putting in. I'll look closer into those, thanks
What about motors that have a trapezoidal back EMF??? BLDCs often have such a backEMF, I guess resultant of the magnetic structure. For these, does it make more sense to have only 2 of 3 phases ever conducting at a given moment, linearly transitioning between say A->B, then B->C. then C->A wash rinse repeat
Nice work. I come from a physics background and never really studied some of the more practical applications of physics, like DC motors. I appreciate how clear you are making this. Have you looked at getting your videos onto Nebula as well? I don't know what that would take but I use it rather than UA-cam whenever I can to support the content creators
Honestly I have never even heard of it. I will have to look into it. Thanks!!
In case anybody is struggling with the math at 5:42, I think the math works out to:
ia = -i*sin(theta)
ib = -i*sin(theta-120)
ia + ib + ic = 0
ic = -(ia + ib)
ic = -[(-i*sin(theta))+(-i*sin(theta-120))]
ic = i*[sin(theta) + sin(theta-120)]
using sin(a-b) = sin(a)*cos(b) - cos(a)*sin(b)
ic = i*[sin(theta)+sin(theta)*cos(120)-cos(theta)*sin(120)]
ic = i*[sin(theta) - (1/2)*sin(theta) - (sqrt(3)/2)*cos(theta)]
ic = i*[(1/2)*sin(theta) - (sqrt(3)/2)*cos(theta)]
ic = -i*[-(1/2)*sin(theta) + (sqrt(3)/2)*cos(theta)] // factor out the negative to get the identity to work
ic = -i*[sin(theta)*(-1/2) + cos(theta)*sqrt(3)/2] //just flipping terms to match identity
ic = -i*[sin(theta)*cos(120)+cos(theta)*sin(120)] // converting constants to equivalent sine and cos terms
using sin(a+b) = sin(a)*cos(b) + cos(a)*sin(b)
ic = -i*sin(theta + 120)
Hope this helps others who struggled with the second half
I am wondering what is the factor or reason that causes the presence of number 1.11 in the law of reactance voltage for sinusoidal commutation in DC machines?
Thank you 🙏
In the figure at 8:00 should the beta current be flipped? The plot would show negative cos but i thought we solved for -sin and +cos
Nice Video! I have a question, why does Ia = -i*sin(theta)? what do ' i ' and ' Ia' really mean here?
in this context, 'i'refers to the magnitude of current you are running through the motor to generate a torque (i.e., t = kt*i). whereas 'ia' refers to the current running specifically through phase a of the motor
Why have you taken negative of the currents (ia=-i sin(theta)), so basically why are you assuming that the currents are coming out?
Great question, I do so because of where I set my zero angle. If I had had my zero angle 180 offset from where I have it, it would be positive. But due to where I have my index defined, I needed to define them as I did for them to produce the optimal q axis current.
Jantzen Lee Yes because when I took positive currents, I am getting Iq=-I, so then I guess we will be controlling the negative Torque which we don’t want ?
Is the logic correct
Yes I would say that is largely correct. I don’t know if it is correct to say you “don’t want “ that. Just because sometimes you do want clockwise torque and sometimes you don’t. And if you define your zero point differently, those sinusoids will phase shift accordingly. I hope that helps, if that wasn’t clear let me know and I will try to answer any more confusion
Jantzen Lee Yaya got it now, thanks for the help 😄
@@jtlee1108 Also, what do we infer from id=0, so according to my understanding, now the torque is completely dependent on the q-axis current and not on the d-axis, so this will reduce the torque ripple as well and no additional magnetizing or demagnetizing flux is produced.
So is this logic alright?
where you get the info of this?
its a mix between textbooks, classes, white papers, and video lectures (Texas Instruments has a very useful series which I recommend called 'teaching old motors new tricks')