whats the best RPM range on this motor

Discussion in 'Electrical Systems' started by Boston, Mar 25, 2011.

  1. Boston

    Boston Previous Member

    I've got a 10 amp 24 volt DC motor 2040 rpm that I'm using to drive a geared pump with and I'm curious about a few things. I'd like to use a simple rheostat to set the pressure on the pump head by adjusting the RPM of the motor but that means the motor will unlikely be rotating at its optimal speed. What will that due to its efficiency and power consumption. And will it damage the motor to run for a few hours at a time significantly below its rated speed.

    I've got a fluid pressure regulator that I"ll be using as well to fine tune the pressure but I don't want To much overpressure. The pump head has 1/2 fittings and the pressure regulator has 3/8 so I'm a little concerned that to much pressure might result in added resistance on the pump and end up being even more wasteful than if I simply slow down the motor.

    thanks in advance
    B
     
  2. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 148, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    The motor will happily turn at a lower rpm but the rheostat will dissipate a lot of heat and must have a means to get rid of it. Your motor has 2.4 ohms internal resistance, so with a 2.5 ohms 100 watts rheostat you can set any rpm between <1000 and 2040. At minimum speed both will each dissipate approx. 100 watts.

    And remember that every watt going into the rheostat is wasted. A switching power controller is a better solution.
     
  3. Boston

    Boston Previous Member

    thanks
    I'll see if I can find that power controller
     
  4. Boston

    Boston Previous Member

    I just realized the batteries in my truck are in parallel rather than wired in series so now I have a 24 volt motor and a 12 volt system

    brilliant eh
    I saw two batteries under the hood and immediately assumed I had a 24 volt system
     
  5. Boston

    Boston Previous Member

    the best solution is to just stick a 12 volt motor on it but, it would mean major modifications to the present set up = whopping pain in the *** and after I add up all the parts I'm still looking at $250+ to fit a 12V motor.

    so I'm wondering, could I get two new batteries wire them in series and charge them with the 12V alternator but isolate them with diode bridges = same money without tearing all my hard work apart, and I end up with a few extra batteries.

    thanks
    B
     
  6. Brian@BNE
    Joined: Jan 2010
    Posts: 262
    Likes: 13, Points: 18, Legacy Rep: 151
    Location: Brisbane, Australia

    Brian@BNE Senior Member

    You do like to make things complicated, dont you? What about an inverter or transformer?
     
  7. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 148, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

  8. Boston

    Boston Previous Member

    hey Brian ya, I'm an over complicate it magnet what can I say, but my stuff does turn out pretty cool by the time I get all the kinks worked out. Once I get this electric figured out then its on to the heating element for this thing.

    OK CD great suggest, just one glitch, I have two batteries in parallel now, so if I add a third I'll have a dissimilarity that will adversely effect battery life if nothing else. I could add two batteries and have two in parallel on each side of the circuit, that would at least balance out the draw on each set.

    hmmmm two batteries aren't all that expensive so I think that wiring plan would work fine, assuming my thinking is correct on being able to balance the system I have by adding two bats instead of just one.

    Brian
    I think a transformer would work but its way more costly that a couple of batteries and a switch. I'll look it up and see what I can find but I suspect its going to be the more expensive option

    thanks guys
    B

    [​IMG]

    I'm a bit fuzzy on what exactly the head lights are doing for me but they are a good indicator of power on and power off.

    the latest configuration of the tank
    I had to move the pressure regulator to the other side of the first filter set which also shortened the overpressure return line and loop the feed line off the pump head but all in all I kinda like it better this way. I'm still fiddling with the centrifuge/pressure gauge/feed line configuration.

    [​IMG]
     

  9. Boston

    Boston Previous Member

    Ok found a converter http://www.powerstream.com/dc24.htm seems like its pretty cheap but it does mention voiding warranties, not sure what thats all about but it would end up being the simplest and cheapest solution at $154. also might make a nice in line oil heater.

    Thanks Brian
     
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