Author
(Search on Youtube for “holiday night fever commercial” before reading!)
There are reasons why you should be or not be happy that the Christmas holidays are coming and the year 2024 is looming. It all comes back to two simple questions: how do you judge your 2023? How do you see the incoming challenges in 2024?
This is a post on KTH pages related to work, so I guess it is about work that we should discuss. However I want to make clear one thing: there is no work satisfaction (or dissatisfaction) that should impede you from having a healthy, balanced, interesting life outside the office. Sacrificing your family, relations, and friends chasing your career is not going to work forever. Sooner or later you will pay it back, in one way or another. You are warned!
So how do we feel about EMD 2023?
I’ll speak for myself, then everyone else in the team can express their views in separate posts…
I have referenced to a Youtube video showing the latest advertisement for a US credit card. It is not about the credit card I want to discuss (throw that part away from the video) but of Santa Claus himself. Do you know who is Santa in the video? If you are not too young, you should have recognized John Travolta, stepping back years in his role as the Italian-American Tony Manero in “Saturday Night Fever” (1977). The sketch also retraces some of the initial sequences of the original movie.
I have always admired John Travolta’s dancing prowess and I think it combines well to Santa’s main character to create a cool happy dude. That’s the same I feel about the past year at EMD. But I cannot dance like that so I let someone do it better :-).
There are many things that make me think positive about what we did. For the first, we must underline that the overall funding situation for our field of research is not the best you can find out there, with funding agencies largely ignoring the importance of electrical machines, their design, and their control for the great goals of sustainability. But I stopped complaining too much about that because we managed anyhow, and there are reasons to be happy beyond that.
Teaching is going well, very well indeed. Every year I get a group of students who enter the course EJ2201 Electrical Machines and Drives completely unaware of what is coming and get out of the course overwhelmed – with knowledge 🙂 . I can see that many develop an interest in the subject after going through the course, which is a good sign. Others are there only because they are forced to, but still, they seem to have a reasonably good time. All in all, I think that this entry course is very important to establish connections.
For those bold students that decide to continue on the path, from 2023 I have been also appointed responsible for the course EJ2230 Control in Electrical Energy Conversion, which is essentially control of electric machines. I did not have much time to make modifications to its content in 2023, but I am now almost ready for the next 2024 round, and I am excited about that.
I have also received great help during these three last years to keep alive the course EJ2222 Design of Electrical Machines, which came under my responsibility after the passing of our dear colleague Oskar, but that I never had time to develop as it has always been overlapping with EJ2201. Mats has helped me significantly to keep it going, and I will always be grateful for that. Now the situation has changed: I have reshuffled the courses along the year so that EJ2222 does not clash any longer with any other course I am responsible for. So! Are you really interested in electrical machines and drives? Join the master of electrical engineering at KTH and you will be able to:
- join EJ2201 in the first semester, period 1 and period 2, August to December;
- join EJ2230 in the second semester, period 3, January to March;
- join EJ2222 in the second semester, period 4, April to June.
And if you do not have enough of me for an entire year, then you can continue with individual project courses and the master thesis, of course :-).
For those who think that teaching is heavy and a waste of time, I have nothing to say. To me, it is a great source of inspiration, recruiting, and a way to send good students ambassadors to work in the industry – which pays back later on ;-).
I mentioned industries. Yes, Sweden has many in the field and the opportunities to collaborate are also significant. Here the strangest of things happen. I could find 100 things to work on in collaboration with interested companies that would support us. However, the financial side is always an issue: a KTH doctoral student – plus all the overheads – costs a lot of money, and companies do not feel like paying that much without an additional external financial support. I can fully understand them – we are so damn expensive. And so we find ourselves writing applications to funding agencies, with the hope that the latter will recognize the importance of our work… sometimes it goes through, sometimes it does not. We’ll keep trying!
However, there is one company that said no, we do not need to play this game – I will pay you all. Those guys at ABB that decided that are amazing and I am really grateful. And scared: because we have a big responsibility to show the value of the money they invested in us. To be continued in 2024!
Let’s not forget, however, that in 2024 we will run doctoral and post-doctoral projects with many involved companies with big names. ABB, Scania, Volvo Cars, CEVT, Inmotion Technologies, and the little but interesting Zparq AB will be around us. We will deliver and learn a lot from them too.
All of this is not possible without the people – it is always about the people. With the EMD people you go on the safe side: give them a task and they will not disappoint you. On the contrary, they will surprise you with the depth and understanding of their work.
There is too much I could write for each of them and this post would become endless. But I can say this: when I realize that I do not fully understand what they are explaining to me about their work, and therefore I need to search for technical details in my old books and notes, that’s the moment when I feel my mission accomplished. This person has turned into a Searcher (not a researcher… re-searchers are re-searching things, while Searchers bring new things). We have only Searchers at EMD – I can guarantee that. I am proud of their work and how they are growing into their role, and I will support their next steps whatever road they want to take.
Ah yes, on the side of everything else, I also accepted to become deputy head of our division Electric Power and Energy Systems. So far I have been taking care of the “social side” of the division, organizing coffee breaks with sandwiches and pastries (the Swedish “fika”!) and information meetings. In the future, who knows. But it is nice to get in contact with other doctoral students working in other research groups – it gives you perspective, and a feeling of an enlarged family.
Let’s hope we can still be all John Travoltas at the end of 2024. So far so good! Merry Christmas and happy New Year!
Author
Greetings! We hope this post finds you well and that you have enjoyed the holiday seasons. In Sweden, it is (still) fairly common to send postcards for Christmas to your nearest and dearest friends and family. I always appreciate the nicely decorated cards and the warm wishes you get from people spanning from your mother to your old primary school teacher.
This year, a very special message reached my Ph.D. student colleague Yixuan and me in the days between Christmas and New Year’s Eve. Our paper, Pole-Transition Control of Variable-Pole Machines Using Harmonic-Plane Decomposition, was approved for publication in IEEE Transactions on Industrial Electronics and the associate editor and reviewers congratulated us for having successfully passed the scientific needle’s eye known as the scientific review process. %Indeed, this marked a cornerstone in our ongoing research.%
At this point, you may wonder what grants this process such an uncanny metaphoric epithet. This blog will try to give a glimpse of what Yixuan and I experienced in the past year and describe the scientific review process from a practical view. In other words, we’ll set out to review a review. Feel that meta-discussion!
All of us have personal experiences with reviews. As a matter of fact, we were reviewed every time we got an exam back at school. And most of us have gotten stuck in front of a product, film, or book review on Youtube or in a newspaper. The scientific review has similarities with these types of reviews, but also some distinguishing differences.
Let’s start with the similarities. Indeed, one part of the review is a score (humans love numbers – see the book Sifferdjur by prof. Micael Dahlén), or in other words, how well you have performed. Some journals or conferences hand out a grade based on the average of the reviewers’ opinions regarding e.g. technical content, novelty, and language. Others, like the review we just went through, give a summarizing statement on the opinion of the reviewers and a pass/fail type of judgment. Either you get a pass (accepted) or fail (declined), or you are informed that the paper has to go through a minor or major review to be accepted. In our case, we went through five agonizing rounds of revisions before the manuscript was accepted after more than a year.
That brings us to a major difference to, for example, a film review. Whereas the film review is carried out on the final product, a scientific paper review happens before the potential publication. Moreover, the reviewers are incognito to ensure their integrity. The reason for these differences is dumbfounding simple and reasonable. In the world of science, quality is less of a taste thing and more about complying with specific standards on how to conduct experiments, display results, and analyze their validity. In order to cross these bars, the reviewers’ jobs are to find flaws in your argumentation and iron out any uncertainties that may be caused by the way you present the results. The review is in a way also a coarse filter whose mesh density each journal can decide on, on their own. Perhaps, the journal has a very defined theme and a high citation score, which puts even higher demands on the scope, standard, and novelty of your paper. For those of you unfamiliar with the term citation score, you can think of it as a reputation rank. Being published in the journal with the highest citation score is for the researcher the equivalent of performing at Carnegie Hall for a violinist.
A third interesting aspect of a scientific review is the correspondence of ideas and arguments that go back and forth between the reviewers and the manuscript authors. Questions from the reviewers are not always answered directly by making a change in the manuscript. Rather, longer answers, arguments, opinions, and explanations may be attached in what is called a review letter. This is a sophisticated way of settling disputes, although I would have liked to try the French combat way at some point.
An example of such an argument in our case was the presence of a small but evil ~100 Hz harmonic on the torque measurement. One reviewer highlighted that it was visible in one of our plots and shouldn’t be there if our proposed control was correct. However, Yixuan and I noticed that the ripple was caused by a resonance frequency in the mechanical structure of the test bench (it is very big and heavy). The first thing we did to try our hypothesis was to jump outside of our cell. When we did that, there seemed to be an amplification of the 100 Hz signal of the vibration we were causing. Then, we moved on to use a commercial drive and motor on our bench and we still observed the same ripple, independent of speed. So we conveyed these measurements to the reviewer and could settle this issue. After the review rounds, I was performing locked rotor tests at varying frequencies on our machine and it was peculiar to hear and feel the humming due to the resonance when I passed 100 Hz. At least, I know where it comes from. Otherwise, I would probably have become a bit bewildered.
In the end, did our paper get better from all the review rounds? The answer is undeniably yes, although the incremental improvements became smaller the further into the process we got. The system appears to work. Kudos to the reviewers!
Author
Another year is going to the archives. As it usually happens, the final rush to close any open issue (or to push it to someone else on the very last day so as to clean your table, but not the others) is ongoing. It takes the life out of people.
But hey, the last days before the Christmas and New Year holidays are also a time of reflection. What has gone well and what has gone bad this year?
I start with the bad things – so we can conclude in a crescendo with hopes for the future.
Bad thing 1 – no Italian food from Santa this year
One thing really hurt me: I did not manage to make a delivery from Italy happen before this holiday season. It was supposed to be a small Christmas present for everyone on the team, something to eat (of course). It all went to the trash. Why? Because of the KTH Innovation incubator for spin-offs!
Let me explain. I ordered a package on Amazon.it to be delivered here at our laboratory address. It has worked last year, so I was pretty convinced that there would have been no troubles this year either. Amazon updated me that the packages were two instead of one because one of the items was located somewhere else, but ok. Both packages were sent without problems, according to the given time schedule, with some days of difference in between.
I was eagerly waiting without saying anything to the rest of the team, hoping for a surprise. I did not receive any information from Amazon so I supposed that everything was fine, until an SMS came to me on Sunday, two weeks ago: “Your delivery was attempted several times but no one received it. The delivery is canceled”.
I jumped on Amazon.it and saw that indeed, a delivery attempt was made, by a rather-known local delivery company that Amazon is using in Sweden. This company is actually a spin-off from KTH and has its roots in the KTH Innovation offices. I will not mention it directly but you can guess :-).
The attempt was made on Saturday for the first time, and on Sunday for the second time, with obviously no success because no one was in the office building. So the delivery company decided to send back the package to Amazon. This was the first of the two packages, and luckily the smallest of the two.
On Monday I called the company and explained that they should deliver during normal working hours. They said, OK! And ten days later, I receive a notification from Amazon that the second package is on its way back to Amazon, and the delivery is canceled. Not even an SMS. Looking at the tracking of the package, it looks as if the second package was sent back and forth within the delivery company, with an attempted delivery on Saturday afternoon. I called the company and they explained that they lost the package that was supposed to be delivered during working hours, then they found it again, and scheduled it for a Saturday delivery. And that they cannot do anything about it now because it has reached Amazon in its return path.
Apart from the anger and the sadness, I am amazed at the level of unprofessionalism. I will fix this issue in January, hopefully by relying on some other delivery company that has no KTH connections.
Bad thing 2 – funding agencies, we do exist you know?
Oh well, of course, we are always struggling to get funding for our research activities. That is not something new for anyone working in academia, so it happens, again and again, that our financial applications are rejected. Sometimes they go through the process and we secure new people, so it is not bad all the way. But when it goes bad, often you remain with the feeling that your application has not even been read by anyone. That does not really give trust in the process. But again, we are stronger than that. We will survive it.
Bad thing 3 – our newest hardware enemy, the TI Piccolo F28069 evaluation board
Sometimes you want to be innovative, and things fire back. We had the original idea to use this evaluation board in a setup with a small six-phase induction machine, for working on the diagnostics of electric machines. The attractiveness of the board came from the fact that you can essentially program it through Matlab/Simulink in a very rapid way, at a pretty low cost. All of this would be true if only the board would respond in a deterministic way to our programming attempt. But it is not… and the debugging of it is equivalent to finding the Holy Grail.
The behavior is simply impossible to debug, signals are either not reaching the board or not coming back to the host computer, and the interrupt-based routines we need for our work are not supplying the inverters with the correct pulse-width modulated signals. Even the pre-made examples in Matlab/Simulink do not work. All of this is making Gustaf very upset and sad. And Gustaf is the nicest guy I know. If you managed to make him upset, you have gone a looooong way…
I will personally trash the board when we are done with the work we are supposed to do. With no mercy.
A little update: Gustaf seems to have found something of interest that could make things work… let us not celebrate too early, but I am ready with the axe to destroy the whole bench to conclude our experience with it.
Good thing 1 – a new Knight and a new Dame of the realm
Let us move to the good things, then!
We had two newly nominated Knight and Dame of the realm, respectively in June and November this year 2022 (for details on the meaning of the noble title, please refer to the previous post “The noble life of the academic“, 2021-12-23).
Giovanni was nominated Knight of Condition Monitoring in June, with a dissertation on the predictive maintenance of motor drive systems. He demonstrated that it is possible to determine the aging of the stator winding insulation (one of the major causes of faults in electric machines) in a real-time fashion, by analyzing parasitic oscillations of the phase currents that originate from the pulse-width-modulated nature of the voltage supplied by a frequency converter. Three journal papers out of that, an experimental setup working as a clock, and a massive amount of gathered data.
I am personally very happy to see Giovanni become a Knight for several reasons. The first is, Giovanni and I know each other for a long time and have been working together since 2011 at ABB. He moved to KTH in November 2016 to pursue a Knight title, while I still was working at ABB. He thought he got rid of me. Unfortunately for him, I became Viscount at KTH in 2018. The moment I was in, I became again his supervisor. I imagined he cried all night when he learned that. Now he managed to get rid of me again, but I do not have the strength to follow him. He will have to do it without me – which means, he will become a successful CEO of some company soon.
The second reason is that Giovanni fulfilled one dream of mine, which is to destroy an electric machine, finally. Some of you may have read my biography and understood that I have five blown-up converters in my career. It is the highest and the lowest point of my career at the same time. But I never managed to kill a machine. Giovanni did that for me: he was supposed to accelerate the aging of an induction machine to fit the goals of the project within the Ph.D. times. He subjected two prototypes to the worst overheating and overload conditions, with me on the side, blood in the mouth, and drooling saliva, inciting for more. When he killed a prototype after six weeks of continuous electromagnetic and thermal stress (while gathering all the important data he needed), I felt a sense of accomplishment. Thank you Giovanni for quieting my thirst for destruction.
Last November, Konstantina became a Dame of Finite-Element Simulations of the realm, too. I have not been involved in Konstantina’s project that was established before my arrival at KTH, and had as the main supervisor our former colleague Oskar that has unfortunately left us. Sjoerd helped during the last part of the project. I have seen the struggle in the finite-element simulations of the variable phase-pole induction machine we are dealing with in other projects and the optimization of an axial-flux induction machine based on the same variable phase-pole principle. I hope we can continue working towards this design direction, in the future, because we need to know more about it. But we all thank Konstantina for her time at KTH, where the brutality of men at work was softened by a female presence that quieted our behavior.
Good thing 2 – becoming Count of the realm
The academic career path in Sweden has a middle stage between Viscount and Marquess that must be achieved for several reasons – one of which is that you cannot formally be the main supervisor of a Ph.D. student without this title (informally, you can… but formalities are all when it comes to career progression).
The title is achieved by following pedagogical courses and by demonstrating to be part of a supervision team (as co-supervisor) of a Ph.D. project from inception to the end. I managed to spread the courses and fit them in my calendar over the years and I must thank the pandemics to have made it possible to follow courses remotely (yes it helped my calendar a lot!). The second requirement was achieved with Giovanni’s project, another thing that I must thank him for.
So now you can call me The Right Honourable Luca Peretti, Count of Electrical Machines and Drives, Lord of Multiphase Drives, Knight of the Order of Parameter Estimation. Remember it in your email conversations with me!
Good thing 3 – the massive scientific advancements of the Ph.D. students
Ph.D. projects are always very non-linear in their advancements – sometimes nothing comes out of the pipe, some other times it is like opening the water taps. This year we are flooding the floor with water.
Gustaf, Yixuan, Omer, and Mesfin have done such an excellent job with our variable phase-pole induction machine, that I could basically tell them to stop working on new scientific challenges, focus on the publications of what they have on hand, and finish their Ph.D. work earlier than the due time.
Just to mention a couple of highlights: Gustaf and Yixuan finally managed to publish the cornerstone paper of the whole theory and experimental work we are doing on the variable phase-pole machine, demonstrating that the previous literature statements (“it is not possible to control a variable phase-pole machine during the pole transition…”) are not true. It is a matter of modeling – choose the right one and you will be able to do that. Stick with the standard models, and you will NOT be able to do that. I remember that I fed both Gustaf and Yixuan the very initial rudimental idea of the unified modeling we use today, back in January 2020. These two guys run like squirrels in a squirrel cage (pun intended) to develop the whole theory with solid mathematical bases, build up the experimental setup (just a 36-leg converter connected to a machine with 36 independent currents, with DSP+FPGA control of all currents and speed), test successfully the theory while repairing, again and again, the hardware faults, and publishing a paper on the IEEE Industrial Electronics transactions in 2.5 years. They need an honorary Knight title already now. The road is downwards for both from now on, and Gustaf, despite the Piccolo F28069 board (see “Bad thing 3” earlier up), you will make it easily and successfully – your growth goes beyond the struggles.
Omer, on the other hand, decided to make an even more stunning bench of the same type working at ABB. I am impressed by its robustness and flexibility, as well am very happy to see that you can use standard ABB drives (with overridden control, though) to control the variable phase-pole machine. Did you know that the machine on that bench was manufactured in 2017/2018 while I was at ABB? It was my last effort together with Ingo (or beloved lab technician at ABB) before leaving the company. I always dreamed to use that machine again, and luckily you appeared in 2020 as a doctoral student. I know it is in good hands now.
Mesfin has also fought his way through the traps in COMSOL to produce a work that is currently under revision as an IEEE transaction paper. What is very special about Mesfin’s work is that he is 50% deployed at KTH and 50% deployed at the University of Addis Ababa, in Ethiopia, making the planning and execution of the work quite a challenge. But you are making it, and we will help you with your last stay at KTH next year. You will soon see the light at the end of the tunnel.
Good thing 4 – we are sailing
For a while, it has been a little dream of mine to work on electric boats. The occasion came and I grabbed it – we must thank in first place Ivan Stenius for his leading role in the hydrofoil boat projects at KTH, as well as Nicholas Honeth to provide a strong link between the electrical and the mechanical world of this application.
We managed to gather resources for a postdoctoral researcher working in the field of electric machine design for electric boat applications. And we also found an excellent and willing candidate in Zhaokai, who recently joined our team in November. I hope we will create all the opportunities you deserve here at KTH, and I think we are already on a good path.
Good thing 5 – new recruitments coming in
Despite the many struggles – see “Bad thing 2” before – we managed to secure 3 new Ph.D. positions for next year, with a fourth that could easily be a shared project with another team in the department. We should be pretty satisfied with that. The recruitment process and their integration in the department will require some time and effort from me and Mats, but I am positive that we will find excellent candidates with lots of passion and willingness to do good. I am looking forward to the candidates’ selection!
We are also still waiting a positive response for the Swedish Immigration Offfice in relation to another postdoctoral research position that we filled in last autumn. More on that when the person will be in place, here with us!
And let us not forget our guest researchers, present and past.
Xinpo, you started with us in November and will stay one year during your Ph.D. studies at Harbin Institute of Technology. I am looking forward to applying your control knowledge in our variable phase-pole machine – we need a pair of fresh eyes there!
Akbar and Dario, it was a pleasure to have you here during 2022. There are things that we need to complete together to achieve the target of joint publications, but we will get there soon. I hope you found the KTH period as formative and useful as it was for us. Personally, any time someone brings in new ways of thinking and new experiences, I find that the EMD team has become a little bit wiser and richer.
Good thing 6 – our teaching and our ambassador students
It is no news for those that work with me: I put significant efforts into developing courses for our master students at KTH. For someone, like me for example, teaching is fun, but there are other important reasons.
One is that I strongly believe in good teaching as a way to improve the competitiveness and long-term well-being of the industrial scenario around us. We are lucky to have many large companies in Sweden that are heavily involved in the electrification of different sectors, and that are looking for well-trained engineers. We try to provide them with what they need, but it is still way too few with respect to the demand. We should produce more electrical engineers.
How to reach that? Well, we can do as many campaigns as we want. But if the teaching is not up to standards, we will always fall short. That is why it is of the utmost importance to have courses with modern content, using modern learning methods, and open to continuous developments to incorporate the latest findings of the research. The students going through our education will also be de-facto ambassadors of our methods and beliefs, once out there in the industry. Better showing the best of us while they are at KTH.
By the way, I find the course development an excellent occasion to put myself in front of the mirror and ask myself: did I really master this topic that I want to teach? Is it relevant for the future? Do I need to know more about it to be able to transfer it to the students?
My father always said: if you want to teach one thing, you need to know at least three things more. I agree completely, now that I am in the middle of it.
I think that we are having reasonably good success with our teaching, looking at the number of students with the role of Gentleman/Maid or Esquire/Madame (see again the previous post “The noble life of the academic“, 2021-12-23) that we supervise every year. Next year will be no exception.
But I am looking for other challenges coming down the line:
- The course of Electrical Machines and Drives needs its own book. I have started working on that, together with my former supervisor in Italy. It will take years, I know. But it must be done.
- The course of Design of Electrical Machines needs to be re-established as a key one in the master program of electrical engineering. This course was Oskar’s and he was doing very well with it. It came under Mats and mine responsibility when Oskar, unfortunately, left us. We have managed it at a minimum, also because it runs in parallel with our other courses. But the situation will change next year, when the course will be moved to another semester, away from our other teaching duties. I am planning a good revision and alignment of its content. It will resuscitate again!
- The course of Control of Electrical Energy Conversion is changing teachers too. From next year, Xiongfei and I will be teaching this course. Its content has a lot of drive control for electric machines, and I am looking forward the collaboration with Xiongfei to establish it as a cornerstone course where students can acquire the principles of controlling a machine-connected and a grid-connected converter at once. After all, the theory is all the same, with some small changes!
Stop writing in this post
Yes I know, I went too far with the information contained in this post. I may have forgotten something actually. Sorry for that. Anyway, take it just as a reflection of our genuine efforts and strive for achieving, and offering, the best research and education in electric machines and drives.
The EMD team deserves a vacation now, and despite being without Italian food (see bad thing 1 earlier in this post), I hope you will find peace and serenity during this holiday season. Lay down your weapons, go home and rest before the battle commences again in January.
Merry Christmas and Happy New Year to everyone, EMD team members and not.
Author
Hello folks,
another update from PhD studies. This time, I would like to share how it is to go on a conference. I attended IECON 2022 “48th Annual Conference of the Industrial Electronics Society IECON 2022 Conference” in Brussels in Belgium, where I presented my paper “Fault Detection in Variable Phase-Pole Machines based on Harmonic Plane Decomposition”.
The conference took one week from Monday morning to Thursday evening. So, on Sunday I took a plane to Brussels. Well, unluckily for me it didn’t go according to plan and I arrived at midnight at my hotel. Grab some food and going to bed, since on the next day, the registration and tutorials are at 8 in the morning.
At the registration, I receive a batch (important!), which will be my entrance to the building and also my ticket to receiving food in the next days. I also get a leaflet with the program as well as access to WiFi. With the organizational stuff done, I head further to the tutorial sessions.
In the morning, I decide to attend a tutorial by the Aalborg University about Wide-Band-Gap devices in wind power applications. Especially interesting is the presentation of their newly built medium power lab.
In the afternoon, I decide to go in a completely different direction and attend a tutorial by several universities from Japan about artificial intelligence in motion control. Oddly enough, the professor starts talking about Japanese pancakes. However, this is their example of a robot applying different ways to learn how to prepare such a pancake without human guidance.
The second day starts with a keynote speech by Katherine Jensen from the European commission with their approach to evaluate developments in research for decision makers in the European Union, a nice insight into how our work may end up influencing the policy.
But now, finally the sessions start. The day is divided into a morning, an early afternoon and a late afternoon session with several parallel sessions. The most important is to keep track of the time table and best to prepare the day with marking the presentations one would like to listen to. Once there it is running from one room to the next one. Mostly I am attending the machines and drives and the electric transportation sessions.
After two days of running around, speaking to people in the coffee brakes and during lunch, I have the chance to present my own work to the audience. Early in the morning, some people are there. I have 15 minutes time to talk about the content of the conference paper and some minutes to answer questions. As always it is very difficult to present a research content in such a short time, but I think people got the idea and some more know about the research focus here at KTH. If you are interested, here is the conference article.
After the presentation I get into a discussion with some interested PhD students from other universities over multiphase machines in general. In the following days, the conference organizes a gala dinner and on the last day the closing event is at an international food court. Over a drink we discuss the conditions and experiences of being a PhD student in different countries. I meet some of my peers I met earlier that year on a summer school in Italy. One cannot underestimate the value of such exchanges.
I decided to stay on day more to explore the city of Brussels and visit some museums, after a week listening to highly specific topics, running around and hustled food, it is a welcomed calm break. It would be a pity only to see the picturesque city from the conference venue.
To put everything in a nutshell, a week of conference was more exhausting than I expected but it is a good chance to get out of the own bubble to see what others do and advertise for the own research as well as a good chance to see some nice places.
Author
It is always fun to disassemble something without the burden of reassembling it!
This time an ancient induction machine, MT71B14-4, manufactured by ASEA (The “A” in “ABB”) becomes my victim.
This guy. Let’s do it!
The nameplate says that this machine is rated as class B according to the IEC standard 34-1-1960. Its rated power is 0.37 kW, rated rotating speed is 1400 rpm, and rated power factor is 0.69. If the “Y-connection” is adopted for the three phase of stator windings, its rated linear voltage is 380 V and rated current is 1.3 A; while if the “Delta-connection” is adopted for the three phase of stator windings, its rated linear voltage is 220V and rated current is 2.3 A.
The connection methods of electrical cables for them are illustrated on the backside of its lid.
Obviously the “Y-connection” is adopted for the three phase of stator windings.
The non-drive end has a centrifugal fan which helps cool the machine with forced air convection.
The cover with louvers.
The cowling which guides the airflow into open channels between fins on the casing.
The fan has radial straight shape blades, which makes it able to work in both rotating directions.
The endcap, which fixes the position of the bearing and support it.
The flange in the drive end, guessed to be used for connecting with the load machine.
There are 24 slots in total for the stator.
Random windings are used for this kind of small size squirrel caged motor.
Rotor bars are skewed to improve the starting torque, prevent the magnetic locking between the rotor and the stator.
A common ball bearing is used in this machine.
There are two washers below a specific bolt at the end ring to balance the weight of the rotor.
Where are my chainsaws? Now I will cut these endwindings off…
P.S. Thanks to Jesper Freiberg for the help in the disassembling process.
