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90v/100a DC Power Supply

Discussion in 'Power Electronics' started by Lester Thunder, Sep 8, 2016.

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  1. Lester Thunder

    Lester Thunder

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    Sep 8, 2016
    Hello to all.
    I'm new to electronics and to this site, as such my questions will be vague and I'll likely have to google educate on some of the terms used to answer my questions. Thanks in advance to all that wish to help.

    I'm working on a redesign project from scratch. I need to run 3 motors (all variable speeds). These motors will be controlled in a fashion that they will receive voltage data from sensor arrays to adjust the speeds of each motor individually.

    I've done a small amount of research on power supplies, VFDs and the like, but have yet to encounter what I think I may need. Each motor would need to be able to draw a max of 30-40 amps at a time (testing will give me the max amps per motor). So to the question...

    Is there a way to build a 90v/100a DC Power Supply that would ba able to handle the load of all 3 motors at once...so that I don't have to build 3 different power supplies? I feel that it would be more cost effective to build 1 power supply.

    Also, given the question above, what would be a logical path forward?
     
  2. Minder

    Minder

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    90vdc: so i assume you are using DC brushed motors?
    They are fairly large current rating for a 90v motor, do you have them yet?
    For 90vdc you would need around a 65vac source, if a regular linear supply.
    Are the motors going to be drawing maximum current simultaneously?
    The cheapest way would probably be to use a Diode/SCR bridge type controller, they can be connected directly across a 120vac service supply, KB market these for 9ov motors and they can be picked up on ebay fairly regularly, if necessary you could upgrade the bridge components to take care of the motor currents you are expecting.
    Do you already have any controllers?
    M.
     
  3. Lester Thunder

    Lester Thunder

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    Sep 8, 2016
    I don't have the motors yet. My assumption is that the max amp draw would be around 30 amps and probably half that continuous. The motors will be brushless.

    I'm designing the motors now. Actually getting one made so that I can play around with the windings to see exactly what each motor would need to be. I haven't built any of the controllers yet either.

    If it would be easier, I could just make a power supply for each motor. Those could range from 48v to 90v and 20a to 40a. This is best guess at this point.
     
    Last edited: Sep 8, 2016
  4. BobK

    BobK

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    90V x 100A is 9000W. Where are you getting this power? This is well above the capability of residential wiring. So is this industrial 3-phase power? What voltage?

    Bob
     
  5. Lester Thunder

    Lester Thunder

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    Sep 8, 2016
    This single power supply would be intended for 3 motors that would have a max draw of 30a each
     
  6. BobK

    BobK

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    Okay, so 90 x 90 x 30 = 8100W

    Residential circuits in the U.S. typically max out at 240V 30A which is 7200W.

    The 120V circuits are typically 120V 15A or 20A which is 1800 or 2400W.

    Bob
     
    Minder likes this.
  7. Bluejets

    Bluejets

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    Maybe use lead acid batteries. They can handle large initial currents.
    Then re-charge from mains supply.

    Another avenue is perhaps the new breed of batteries developed for the off-line solar grids currently beginning to appear (especially in Australia).

    As usual on here, if you were to present some more detail, then the "ones in the know" may be able to help you a little more, perhaps even suggest improved alternatives.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    What are you doing? Making a flying car?

    Seriously, what are you trying to do? You're well into the realm of high power electronics, certainly not something for a beginner.
     
  9. BobK

    BobK

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  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Hey, weren't you going to put that in an 8oz. Mailer bag and send it to me?
     
  11. BobK

    BobK

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    Sorry, I tried to but I hurt my back trying to lift it and ended up in the ER.

    Bob
     
  12. hevans1944

    hevans1944 Hop - AC8NS

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    If you sell it on Amazon, maybe they could deliver it with one of their 'copter drone thingys...
     
  13. Lester Thunder

    Lester Thunder

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    Sep 8, 2016
    Ok...so maybe a little More clarity is needed. This project will have three BLDC motors that may require a lot of power to startup, but should run in the ballpark of 5a to 15a. I can setup the startup of the motors so that they will never hit full load requirements at the same time, but they will all run at the same time so there should be enough available amps to perform the work. So let's assume for now that I would need upwards of 45a to do the work.

    My question was driven to help me figure out if a single DC power supply would turn out better than 3.

    Bob K. I have residential circuits in my own home that are higher than 30a. My A/C unit is 60a. Thanks for the link to the Variac...goingook at that now.

    Bluejets. Definitely do not want to use batteries.
     
  14. Minder

    Minder

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    Seems a rather ambitious project to build BLDC motors, especially of that power rating, do you have a source of rare earth magnets for the rotor?
    Or are these going to be outrunners like the Fischer-Paykel.
    M.
     
  15. Lester Thunder

    Lester Thunder

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    Sep 8, 2016
    Neodymium magnets.
     
  16. Bluejets

    Bluejets

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    Running those types of loading off the mains may well just attract the attention of the local supply authority.

    Have you considered approaching them beforehand to get their ok...?

    Just that they normally don't take too kindly to large surges that their equipment may not be able to handle and affects that flow through the grid to other consumers on the same trannies.
     
  17. Lester Thunder

    Lester Thunder

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    Sep 8, 2016
    Either I'm not understanding something or I'm just not explaining in correctly.

    My pool pump takes 27a at startup. It's 220 VAC. It runs continuously at 9a-10a. So on continuous run it is using 1,980-2,200 watts.

    Am I wrong in saying that a 90 VDC motor starting up at 27a, but running at 8a is using 720 watts?
     
  18. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Yeah, but you need to be able to supply the startup current.
     
  19. hevans1944

    hevans1944 Hop - AC8NS

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    Welcome to Electronics Point!

    That's pretty ambitious for someone new to electronics.

    That's nice, but you have failed to tell us what you are trying to DO. You have told us what you think is how to do it (whatever it may be) by saying "will receive voltage data (what's that?) from sensor arrays (what kind of arrays?) to adjust the speeds of each motor individually." From this I surmise you have three BLDC motors, each with its own speed control, all operating from a 90 V DC power supply of sufficient current capacity to supply all three motors simultaneously with their start-up (locked rotor) current as well as a somewhat lower running current. Is that about it in a nutshell?

    The answer is YES. Check out this one available, used, on EBay. This one was apparently sold by Electronic Measurements, Inc. and is called an EMS Power Supply (whatever that is) rated 0 to 100 Volts and 0 to 100 Amps DC, 10 kW output. Requires three-phase power. This type of power supply (with its variable output) is more expensive than a dedicated single-output-voltage power supply, but the price that is asked ($1999.99) is in the right ball park, based on my experience with beasts of this sort.

    You could, of course, opt for three separate power supplies, one for each motor. That is what I would do, given the wide range of current demand among three motors. There will be much less, or no interaction, among three voltage-regulated power supplies providing power to three motors versus one voltage-regulated power supply providing power simultaneously to all three motors. The utility wiring is also likely to be less complicated. You should be able to use single phase power, either 120 or 240 VAC, for three power supplies.

    The cost of power supplies of equal voltage capability is a function of their output power capability. It may cost a little more for three power supplies whose total power equals or exceeds a single power supply, but there are also advantages. Cost of a spare power supply will be less, and if one supply fails the other two still work. Yada, yada, yada. Buy or build three power supplies is what I would do, given the limited amount of information at hand.

    Coming here is a decent start for a newbie in electronics, even if you are an expert in designing large BLDC motors with neodymium rare-earth magnet rotors. i am NOT in such an elite group of designers, but there are others here, @Minder comes to mind, who have extensive practical experience in industrial motor selection, application, and control of same. They need to know what you are trying to DO before they can give you any useful advice on how to do it. All I can offer is advice on power supplies, large and small.

    Hop
     
    (*steve*), Tha fios agaibh and Minder like this.
  20. Minder

    Minder

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    Apr 24, 2015
    I am wondering why you passed up the opportunity on using phase vector VFD's and 3 phase motors on 240v 1ph.
    If by going to BLDC is because of positioning, then you would need some kind of feedback element such as encoder and controller.
    If just velocity control I would have thought VFD's would have done the job.
    But there is not all that information as to the application?.
    M.
     
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