DC Variable Speed Drive application

Discussion in 'General Electronics Chat' started by aquarius, Mar 14, 2009.

  1. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    I have DC variable speed drive with 90V DC, 10Amp output. This drive can be controlled by 0-10V input signal. I have controller with temperature sensor which has 0-10V output.
    I'm going to use controller and drive to regulate speed of 12V DC , 4Amp fans.
    Please advise how is it possible to do this by using DC VSD and controller.
    Thanks.
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Do you mean that you want to power the 12 Volts fans with the 90 Volts powersupply ?
    Or do you want to make a seperate VSD for the fans ?

    Greetings,
    Bertus
     
  3. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    Yes, I want to run (power) 12V DC fans from 90V DC Variable speed drive.
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    How many fans are involved ?
    The fans will burn if they are connected to the 90 Volts.

    Greetings,
    Bertus
     
  5. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    I can connect as many as it needs. As far as I understand there is an option to connect at least 7 fans in series. Is there any other option?
    Forgot to mention. It's possible to reduce max. output voltage to 48V DC.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    When reducing the voltage to 48 Volts you can have stings of 4 fans.
    The 7 fans string will work on 90 volts.
    The only problem with fans in series is, what happens when one fan fails.
    Does it make a short, the other fans get more voltage and will get defective also.
    Does it make an open connection, all other fans will stop too.

    Greetings,
    Bertus
     
  7. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    I understand. What do you think of using DC-to-DC converter, 48V DC in and 12V DC out.
     
  8. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Then you will have to make a circuit for 12 Volts to regulate the speed of the fans.
    You said you wanted to control it with 0 - 10 Volts.
    You can make a triangular or sawtooth generator with a 10 Volts top to top output.
    Connect this to a comparator input,
    The other comparator input will be fed with the 0 - 10 Volts regulation voltage.
    The result on the output of the comparator is a PWM signal that reacts on the 1 -10 Volts.
    The output of the comparator can drive a powermosfet.
    The powermosfet will regutate the fans.

    Greetings,
    Bertus
     
  9. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    My controler with 0-10V out signal and temp. sensor works perfect with DC VSD.
    How to solve voltage problem. Is there any options not use series connection?
     
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Do you have the schematic of your current speed controller?

    For the minimum 48V output voltage, what is the input voltage? Does the controller get warm when running motors at half speed? If it does get warm, the method described by Bertus, PWM (Pulse Width Modulation) will be much more efficient than the current controller as well.
     
  11. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Putting someting in series with the fan will only be waste of energy.
    When the VSD is working at 48 Volts and your fans are 12 Volts 4 Ampere,
    You will have to "burn" 36 Volts X 4 Ampere = 144 Watts that is useless.
    The best option will be 4 fans in series on 48 Volts, with the risk of some failure the way I have discibed.

    Greetings,
    Bertus
     
  12. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    It's FINCOR 2335 MKII VSD
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    I hope I have found the right manual, but I could not find anything on running at 48 Volts.
    The controller seems to work directly from the mains power.

    [​IMG]

    If this is not correct, please give me a link to the correct manual.

    Greetings,
    Bertus
     
  14. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    Yes, everything is correct. It's possible to reduce max speed to 48V DC output by regulating speed potentiometer.
     
  15. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Perhaps it sounds strange, but how about a voltage divider at the input of the regulator.
    When normaly the 10 volts input gives 90 volts output,
    then 1.333333 Volts input will give 12 Volts output.
    The division ratio is 7.5 : 1, so take a resistor of 6K5 and 1K, and your regulator will work from 0 - 12 Volts.

    [​IMG]

    Greetings,
    Bertus
     
  16. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    I like this idea. You mean I need to make otput signal from controller to DC VSD
    0-1.33V. Correct?
     
  17. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Yes, I think that the VSD will give 0 - 12 Volts at 0 - 1.333 Volts input.
    I hope the fans will run smootly on the pulsed signal from he VSD,
    as I see no capacitors at the output of the VSD.

    Greetings,
    Bertus
     
  18. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Question about the 12V Replacement motors, stated above, they draw 4A. Are they permanent magnet, brushless, or field wound?

    The reason I ask is due to the specifications:

    If running 4 motors in parallel, at 4A each, this is above the specs by 50%
     
  19. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Do you have a link to the specs of the motors ?
    You can not drive 4 motors on the 10 A VSD, You are limited to 2 motors.

    Greetings,
    Bertus
     
  20. aquarius

    Thread Starter Active Member

    Mar 14, 2009
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    I've made all adjustments and checked with one motor. Everything works great.
    Thank you very much for your advice.
    Last question. How many motors 12V DC, 4Amp I can run from VSD in case of 12V DC maximum output.
    I'll remind, from VSD specs: for 90V DC it is 10Amp.
     
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