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IndustryArena Forum > OpenSource CNC Design Center > Open Source Controller Boards > 550W BLDC motor controller modifications for fun.
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  1. #21
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    Re: 550W BLDC motor controller modifications for fun.

    What I have found so far on the VEVOR BLDC 550W "servo" motor/controller set.

    -What they call "SERVO" is not such, it is just a speed controlled brushless motor/ controller with HALL sensor feedback and 2 stop positions (when using the up/down needle attachment).
    -It is not designed for handling midsize or large inertial loads, that is, it will not survive a lot of sudden stops, from high rpms, when used as a medium size lathe spindle, the reason: Lack of resistive brake load. All of the energy in the spinning chuck and rotating part will be delivered back to the dc link capacitors increasing the DC link voltage and stressing the output bridge and drivers.
    -at least the one I disassembled, does not have pulse by pulse current limit, the overload circuit relies on the igbt bridge current developing more than 500 mV on the 0.015 ohm current sense resistor and thus triggering the bridge driver protection comparator (going over the 500mV reference voltage), then the overcurrent protection will trigger when the bridge current reaches > 33 Amps!!

    The individual IGBTs are rated 600V 20Amps, as well as the antiparallel diodes, so the braking current will also stress them. The lack of a decent heatsink will not help either.
    Due to all of the above, it is illogical to think about rotation reversal without stopping, it will destroy the output stage, that's why they used that convoluted way to reverse rotation.

    Off course, all of the above is probably good enough for their intended application, mass production and a low cost product will make them cut many corners. But don't expect too much from them in other applications. The overall board design shares a lot with former ST evaluation boards. Even the set velocity input voltage range...

  2. #22
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    Re: 550W BLDC motor controller modifications for fun.

    SPEED CONTROL USING POTENTIOMETER

    all resistors 1/4 W

    Potentiometer 4.7 k or 5 kOhms 1/2 W or bigger (due to shaft Isolation issues), I used RV24YN20S 5K Potentiometer, you might have to alter the values of R1 and/or R2 depending on tolerances.
    Enjoy!!

    kreutz

  3. #23
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    Re: 550W BLDC motor controller modifications for fun.

    For a faster 0 - Vmax (approx 2 seconds) response replace R2 by 4.7 Kohms and R4 by 180 Kohms resistor (when using 5 Kohms potentiometer). The original circuit in the Rev 001 schematic has a response time of about 3 seconds from 0 to Vmax. I don't recommend too fast settling time because of the lack of a "non-destructive" maximum current limit on the original controller. I don't like to put my luck to test doing sudden accelerations and decelerations, as it was programmed from the factory, don't compare a lathe spindle to a sewing machine's inertia.

    I am also working on a PWM (isolated) speed control and On/OFF, I will be testing it in the next few days.

    Note: If you are using a 4.7Kohms potentiometer keep R2 value at 4.3Kohms.

  4. #24
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    Re: 550W BLDC motor controller modifications for fun.

    This is definitively not the time to do new projects, still most of the parts, that come to mind when planning a new design, are out of stock. Even the development boards. I will continue to work with the ones I have and after getting a solid prototype, working as I want, I will sit and wait for the semiconductor industry to get back to what it was a few years ago.

    I was evaluating the ST motor control SDKs, I had to go back to the previous generation (SDK5.4) since the latest MC-SDK6 is a joke. No examples whatsoever, almost no choices of microcontrollers for the motor control workshop, the information on the internet is for older SDKs not compatible to the CubeIDE, no new video tutorials for the newer MC SDK6 nor information on "how to". The same applies to MATLAB, the new 2022 simulink embedded support package for STm32 controllers is not compatible with the new StcubeMx version, the same for Ti C2000's. We are frozen in time to the times before covid in the software side, but not even near comparison on the hardware side.

    Rant off!

  5. #25
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    Re: 550W BLDC motor controller modifications for fun.

    WHAT IS FIELD ORIENTED CONTROL (and how to control Permanent Magnet Synchronous Motors (AC permanent magnet servos and BLDC) ?

    Here is an explanation:

    https://training.ti.com/field-orient...-magnet-motors

  6. #26
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    Re: 550W BLDC motor controller modifications for fun.

    i think we can add magnetic encoder, maybe it is good brushless servo motor
    long time to see you,
    regards

    Click image for larger version. 

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  7. #27
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    Re: 550W BLDC motor controller modifications for fun.

    We may try, but my opinion is that with only 3 pole pairs and trapezoidal BEMF, there will be a noticeable torque ripple (even with FOC control) at low speeds, at higher speeds the load inertia might help smoothing the torque ripple. The other problem I see is that the compact motor size and the coils' wire size will make it difficult to manage the heat, if we replace the fan blades in the back with an encoder, we will have to provide an external fan to help cooling the motor. As it is now, at low speeds and high torque, the motor will overheat easily.

    High motor temperature is a killer when using FOC control because of the increase resistance of the coils which was not taken into consideration when tuning the PI loops (current and velocity), so some instability will also potentially show that will require some sort of adaptive PI tuning observer added to the FOC controller. It might, of course, improve a lot the low speed stability and noise to include an encoder, but I would not use it for positioning control. Using it for speed control applications will make it less affordable and many will not see an advantage.

    Nice motors you have there, are they high voltage too?

    Best regards, it has been a long time.

    kreutz

    Note: I also have now a 750W motor and controller from the same brand. Courtesy of a friend. So it will be good to compare them sometime.

  8. #28
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    Re: 550W BLDC motor controller modifications for fun.

    my motor is stepper motor only, pic for example magnetic encoder only
    i have st evalution. i will find 750w motor and trying with you
    b.r

  9. #29
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    Re: 550W BLDC motor controller modifications for fun.

    I will probably test the 750 W motor and controller using the potentiometer for speed control, I will post the results and some photos. It is getting difficult to upload videos since the internet speed at my home is so slow... (download speed maximum 3 Mbps, upload speed maximum 500 kbps, although I haven't been near maximum for a while).

    Regards,
    kreutz

  10. #30
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    Re: 550W BLDC motor controller modifications for fun.

    Found this test on the internet, it is the same 550W BLDC motor and controller. The author uses an improvised Prony Brake to do the test.

    https://cdn.imagearchive.com/homemod...ab66150223.mp4

    It illustrates the fact that the controller does not limit the motor current, so he was able to get approx. 5 Nm torque at 1000 rpm which is about 750 W and even about 900W on another test. Of course, the motor will not survive that overload for long.

  11. #31
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    Re: 550W BLDC motor controller modifications for fun.

    I am still working on the dynamometer. Prices for the main components are way off the budget. I need a toque sensor capable of measuring the torque ripple over the noise floor in the 0-15 Nm torque average range, that means that the torque sensor technology should exclude the slip-ring type. but the piezo type are really expensive and the non-contact cheapest is above the $500 mark (and those are Chinese, which means that there are no good specs' sheets to base my decision on). On the other hand, the magnetic powder brakes in the range 0-12 Nm (at > 1500 rpms), are also expensive. I excluded the dc motor, PMSM motors and induction motors from the load candidates because they will provide their own torque variations (due to their own electro-mechanical construction) and that will be measured as additional torque ripple. What is left as the cheapest option for a load is the old Prony Brake... The magnetic powder brakes are interesting since the data sheet also includes the inertia data, and that is important at the time of modeling the dynamometer system. The Prony brake option , in my opinion, is good but it will be difficult to set fixed, reliable loads, for repetitive tests runs. Am I asking for too much? In Spanish they have a popular expression : (3B) or B.B.B. (which translates to: Good, Good looking, and Cheap), that is what am looking for , or better yet, sponsors to provide them temporarily and I will send them back as soon as I finish.

    Of course, If I renounce to measuring the cogging torque and torque ripple in general, then there are cheaper options.

  12. #32
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    Re: 550W BLDC motor controller modifications for fun.

    For motor efficiency and power measurements you can always do something like this:

    https://www.youtube.com/watch?v=1Pd0...ature=emb_logo

    But efficiency and power are only part of the story, and I want to get as much information, for comparison purposes, as possible. I want to make a better controller and prove it, at least to myself, since there is no much attraction to a thread like this (as proven by the lack of comments so far)

  13. #33
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    Re: 550W BLDC motor controller modifications for fun.

    No news, my daughter is moving and all the clutter got its way into the workshop.

  14. #34
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    Re: 550W BLDC motor controller modifications for fun.

    Merry Christmas and a very Happy and Prosperous 2023 for everyone!!!
    All my work is on hold, still have many unfinished projects but they will be left for 2023. My workshop is a real mess and there is still some water damage left from the last hurricane. Luckily is only cosmetic, but some sheetrock boards from the ceiling will have to be replaced as soon as the clutter is gone.

    Best regards!
    kreutz

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