Motor Controller Power Supply

Discussion in 'Power Electronics' started by mattrgs, Oct 7, 2016.

  1. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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    Hi all
    First of all thanks for any help.

    I have a 130V dc motor (1.34 kW) (see attached photo for more information) that I got out of a treadmill. I am using it in a homemade pottery wheels. However currently the controller out of the treadmill is complicated as it is computerised, so not easily changeable and modifications to it aren't possible. So therefore I am looking to fit a new motor controller.
    I don't need to run it at full speed, at absolute maximum it needs to be half speed, if not lower. I have found a number of devices such as this: https://www.amazon.co.uk/gp/product/B016Y027DM that I think would work with it. However all of these kinds of devices require a dc input.
    I have not managed to find a ac to dc converter that reaches a high enough voltage and power output. I am keen to keep this as cheap as possible, so am open to any suggestions.

    Thanks
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Ebay 301875805136 no power supply needed.
    Max.
     
  3. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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    Thanks for your reply.
    Whilst looking at similar projects, another solution came to mind:
    I only need to run the motor at 240 rpm max. Using this simple calculation I think it says I need a lot less voltage: (240/3400)*130 = 9.2V.
    Does this make sense, or do I need to take other things into account such as stalling the motor. I realise that at slow speeds I lose torque, but it is already very powerful, and if I were to use a 12 or 24V power supply I could run it slightly faster and use a pulley to decrease speed and increase torque.

    This seems like a simpler solution if it works.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is OK as long as the load demand does not change at all or very little.
    Max.
     
  5. ronv

    AAC Fanatic!

    Nov 12, 2008
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    Have you considered a pulley?
     
  6. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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    Ronv - I am already using a pulley to bring down the speed, but I need it to be variable whilst operating, and there doesn't seem to be an easy way to do this with pulleys.

    MaxHeadRoom - I would be varying the pen between about 10% and 60%, would this vary the load too much, and why does this matter?
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Try the motor with a car battery as the supply and see if it provides enough torque for your needs. I suspect it won't (unless you have a very small pottery wheel).
     
  8. ronv

    AAC Fanatic!

    Nov 12, 2008
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    You need to get the speed down to your maximum needed with the pulleys. Then when you add speed control you will still have good speed and torque control. If you can't do that you should probably pick another motor.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If dropping the RPM from 3400 to 240 rpm for that 1.5hp Leeson DC motor is a little overkill for you application, equates to ~20HP output.
    You might consider a smaller motor and a worm and pinion gear box.
    Max.
     
  10. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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    Ronv - I was planning to use a 12 or 24v supply, if I use a 12v, that should give me a max rpm of : (12/130)*3400 = 314rpm. I think it is a 1.5 hp motor, and as I need just over 200 for maximum, that would give me 2.25hp of torque, and even if it was a 0.75 hp motor it gives me over 1hp torque which is still excess.
    I was also looking at a 24V supply so with a pulley I can have more power and still achieve low speeds but at a higher voltage.
    Alec_t - I assume a 12V battery wouldn't work instead of a car battery as it wouldn't provide the necessary current?
     
  11. MaxHeadRoom

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    Torque is equal to current, the torque capability will drop in relation to voltage/rpm.
    You need to maintain torque by means of reduction.
    Otherwise you would require some kind of closed loop feedback controller.
    Max.
     
    Last edited: Oct 10, 2016
  12. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    :confused: A car battery is a (nominal) 12V battery.
     
  13. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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    I had meant as in a smaller battery, like the ones used in fire alarms
     
  14. Alec_t

    AAC Fanatic!

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    It might provide enough current, but not for long.
     
  15. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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  16. MaxHeadRoom

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    Why not pick up a MC-60 T.M. ~$40.00 controller on ebay, just plug it in to a 120v socket.
    A 5k pot controls the speed, they also have some degree of current feed back for constant rpm.
    Those SMPS supplies are not that sturdy for a 1.5hp DC motor.
    Max.
     
  17. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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    All of the MC60 motor controller are from the US (I am from the UK) so the cheapest is over £50 with postage, and takes over 2 weeks to get here. So its not the best option.
     
  18. MaxHeadRoom

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    What about the KB/Baldor, any of those on the UK ebay site?
    BTW, does the motor have a flywheel? or has it been removed?
    Max.
     
  19. mattrgs

    Thread Starter New Member

    Oct 7, 2016
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    KB - £65 and above
    Baldor - £110 and above

    It did have a flywheel, but it was cut off, as it was causing issues due to its weight. From experience this hasn't caused an issue, it only means that it comes to a stop more suddenly.
     
  20. ronv

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    Here is another thought.
    Use a 10 to 1 pulley.
    Use a large lamp dimmer and a diode for the speed control.
     
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