Adding Speed Control on BLDC motor

Discussion in 'The Projects Forum' started by diebog, May 3, 2015.

  1. diebog

    Thread Starter Member

    Mar 23, 2013
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    Next project I am working on is re-purposing this DC router motor which was a 4,500 RPM single speed for another application and I need a way to adjust the rpm. Pulleys are not an option the way this will be used. I'm guessing some sort of a VFD will be needed, but I have no clue what I will need or if this is even possible.

    This brush-less DC motor has a transformer box that takes AC 3 phase input and outputs 48 volts DC. It came with the motor/router from the manufacture. Below are some pictures of the tag on the motor, and transformer.

    A variable speed control would be the best but if I had to go with 3 or 4 settings like 1,000 2,500 3,000, 3,500 4,500 rpm or something alike, that would be fine to.

    IMG_2079.png IMG_2081.png IMG_2080.png


    On another piece of equipment there are some dc speed controllers, would I need something like below but one for 3 hp, or is there an easier way to control the speed?
    IMG_1989.png
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The motor would appear to be a 2 pole motor at 48v 3ph.
    Most likely a standard induction motor, and presently fed from a suitable 3ph transformer.
    The Telemecanique Altivar pic is a standard VFD but intended for =>220 3 ph.
    I think you are going to be hard pressed to get a variable speed unit for that voltage (50v 3ph).
    I don't see any indication it is a BLDC motor?
    Max.
     
  3. diebog

    Thread Starter Member

    Mar 23, 2013
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    Well I am pretty sure its a BLDC motor because the motor has no way to change brushes. Its totally sealed up, no vents which is what led me to believe its a brushless motor. I could be wrong here, its just that every motor I have seem that had brushes had some sort of venting in the case. Even the wires going into the case are sealed. Plus it spins by hand with almost no resistance which again made me think BLDC, whereas a brushed motor usually has some resistance from the brushes touching. Is there any way to tell if it is in fact a BLDC? There are no other tags on the motor, just what I posted which is on top of the motor.

    Ill take a picture of inside the transformer box, but other than a few relays and the transformer, there isnt much to it. Maybe it will explain a little more.

    So if a variable speed controller is to complex for what this motor needs, is there a fairly simple way to just cut the speed down in half or possibly in thirds? Kind of like how the bigger porter cable wood routers have a sliding speed control. I realize thats ax and totally different, but more or less the same principle.
     
  4. diebog

    Thread Starter Member

    Mar 23, 2013
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    I also have a second question that has no part of this project, but involves the Telemecanique Altivar VFD. This VFD is on a bridge saw and there are actually 2 of them. One to move the bridge back and fourth and one to move the blade left and right. One VFD is a 1.5hp and the other is the 2hp in the pic above. Now these have a bunch of hookups inside, many which are not used at all. To control the speed three wires are ran to a 5k potentiometer in the control panel to control the speed. So there are 2 knobs/2 pots to control each VFD.

    Now what I would like to do is to control both VFD's with one pot. That way I can sync the speeds together. Reason I need this is I need to be able to move back and right, or back left, forward and right etc. Its for doing a radius, or 45 deg angle which requires holding down the remote control back and right etc at the same time so it equally moves back as it does to the right. Right now I put dots next to each knob to try and get the 2 speeds close. Its very very difficult to say the least to get the speeds even remotely close.

    So I had a few ideas and maybe I am way off base, so hopefully someone out there has done something alike and can offer up some ideas. First I thought is it possible to find a 5k pot with dual outputs and dual inputs so basically a shaft with 2 layers that moved together as one. The searches I did on digikey didn't come up with anything like this. Maybe there is a specific name for this type of pot, if they even make such a thing.

    My other thought was would it work to just wire each set of the 3 wires together with or without some inline diodes on each wire to block the signal from going backwards and use one pot. But I don't know if that would screw things up or what. Ive never used these VFD's so I have no clue what is ok and what isn't.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    BLDC generally means a 3 winding stator the same as an induction motor, which I think it is, BTW.
    But a BLDC only has two windings of the three powered at any one time, hence BLDC which represents a DC motor turned inside out.
    This appears to be a standard 3ph induction motor, albeit a low voltage one.
    There are very few options for rpm control, pretty much the only way is by VFD and I have never seen one for that voltage.
    The only way to control the two Altivars simultaneously is to use a ganged (dual) pot, one section for each VFD, but you are going to be hard pressed to tune/calibrate them to perform identically in tandem.
    Max.
     
  6. diebog

    Thread Starter Member

    Mar 23, 2013
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    Ya I realize it will be hard to get them exact, I just need them relatively close. I found a 3 gang 5k pot on ebay so I ordered it to try it out. There were no dual gang ones in the US. And I didn't feel like waiting a month to buy from china.

    So a VFD is my only option here huh? I wish there were a simpler way. Heck even if I could just cut the rpm in half it would be better than nothing. But is there a safe way to do so? I don't really understand how a VFD works controlling the BLDC motor, perhaps I need to read up some on it. Any thoughts on a good source to learn about the two?
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Digikey has all kinds of dual gang 5k pots.
    You cannot use a BLDC motor on a regular VFD, they are designed for induction motors, BLDC are P.M. motors.
    A VFD takes the AC supply, rectifies it and produces a variable frequency, variable amplitude 3 ph signal to power the motor.
    Max.
     
  8. BillB3857

    Senior Member

    Feb 28, 2009
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    With your motor completely disconnected from anything else, short two of the motor leads together. Turn the shaft by hand. If it turns freely, it is an induction motor, If it is difficult to turn and tends to jump positions, it is a BLDC. Which is it?
     
  9. diebog

    Thread Starter Member

    Mar 23, 2013
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    So I shorted 2 of the wires and even all 3 of the wires to just make sure and it still turns just as freely as before. So it is an induction motor and not a BLDC. What are the differences? Is this bad or good for what I am trying to do?
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    See post #5 and #7.
    The motor ran directly off of a 3ph transformer, you would require a suitable voltage VFD, which I doubt if they are available.
    Max.
     
  11. diebog

    Thread Starter Member

    Mar 23, 2013
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    Ok I get it now. As far as finding a VFD, what vendor would I have the most luck with finding what I need? Didikey, Mouser, Ebay? IS there any "specialty" names its called? Or is it simply just a 48volt VFD? Just wondering what other search names I could use.
    "
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I have used many VFD's over the years and never run into one that low, even 120v 3ph induction motors are rare.
    48vac 3ph are even rarer.
    Makes are Telemecanique, Mitsubishi, Allen-Bradly, Hitachi, WEG etc.
    Max.
     
  13. diebog

    Thread Starter Member

    Mar 23, 2013
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    Question regarding programing the Altivar 31. I found the programing manual online and trying to figure out why one is seeing a different number even though I am using that 5k dual pot. Its way off. I knew it wouldn't be right on, but I thought it would be some what close. So I played around with the menu some getting used to it, and the only menu I am able so see is the last one SUP. Which is just all the monitoring stuff. You cant make any changes here. How do you access the other menus?


    Altivar.png

    I found one menu under the the SUP either Frh, or Lfr but I forgot to write down which one I was looking at. But one of my 2 Altivar 31 controllers said 55.0 and the other one said 40.0 Im thinking this is the max frequency or speed that was setup from the factory when this equipment was made. In fact the one with 40.0 actually never had a potentiometer. It had a jumper between "A1" and "10v" in the pic below. Com, A1 and 10v are the 3 that are connected to the pot. So I just went off how the other one was wired up to the pot and copied it. It works fine, I just need to find out how to set both VFD's max frequency the same so that way they will hopefully be closer. That is what I came up with anyway. Also a side note, when you put a jumper wire between A1 and 10v, it will show the max which again was 55 on one and 40 on the other.

    Altivar1.png
     
  14. diebog

    Thread Starter Member

    Mar 23, 2013
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    I figured out all the programing stuff. I just had to input the master code 6969 on the COD menu and it unlocked the rest of the options. I was able to get both controllers running pretty close to each other.

    Back to the VFD idea, Ive been searching and found this company that makes some lower voltage AC induction motor controllers, the amp ratings are way above the 35 amps my motor uses. Would any of these work? http://kellycontroller.com/AC-induction-motor-controller.php
    http://www.cw-industrialgroup.com/P...es/Sigmadrive/Induction-Motor-Controller.aspx
     
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It would seem that the KIM7210 etc would work.
    Max.
     
  16. diebog

    Thread Starter Member

    Mar 23, 2013
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    Is there a reason why that one would be better then the others? They all are 24-48 or 24-72 volts. The KIM4810 is rated for 24-48v and has the same amount of amps as the KIM7210, so I was just wondering if my motor maxes out at 48v, wouldn't getting a controller that can run 72 be redundant? And also the description says "KIM programmable controllers designed for AC induction motors provide efficient, smooth and quite motor speed control, are suitable for small and midsize electric vehicles." I have zero experience with electric cars and what they use. Is my motor the same type that is used in electric vehicles?

    It also says Nominal batteris voltage: 24V-72V, im guessing this is what it needs to power itself? Sense I have 24vdc in my main panel, that should work the same as batteries I would think.

    I probably should be asking the manufacture all these questions, but just curious your take on it ask you have been around this stuff way more than I have. And I really appreciate your input. So when I talk to them, I tell them I have a 48v AC Induction motor that is three phase, 35amps, and 50Hz correct?

    Here are a few more pics I took of the motor and the inside of the transformer.
    motor side.png transformer 2.png transformer.png trans small relay.png trans relay.png trans label.png trans label 2.png
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Whatever DC supply you use it is going to have to conform to the same current requirements as the original AC supply, it might be advisable to drop the manuf. an email with details of the present motor and see what they say.
    They obviously show low voltage 3ph motor drives.
    Yes yours shows 48v AC Induction motor three phase, 35amps, and 50Hz.
    Max.
     
    Last edited: May 10, 2015
  18. neonharp

    New Member

    May 10, 2015
    13
    2
    That is indeed an odd motor . The only reason that I can think of for using a 48 volt /3phase motor might be electrical safety to keep someone from getting electrocuted . Devices that use less than 50 volts are normally considered safe . It appears to be a totally enclosed motor , most likely intended to be used in a wet or hazardous environment . First of all , you can't run a 3phase motor on DC . What you might try would be to feed the primary of the transformer with your 2HP vfd . Set up the VFD current limit to protect the vfd , and frequency output set at 50 or 60 hz . As long as there is no load on the motor , it should run . Next try turning the speed control of the VFD down to get the slower speeds you want . You may not be able to get it real slow , because transformers need heavier iron cores to function efficiently at lower frequencies . Although I haven't worked with the Altivar drives for some time , and don't have the manual in front of me right now , there are parameters that you can change to "tweek" the operation of the vfd . the voltage/frequency curve needs to be correct or you could damage something .

    Cheers !
     
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