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  • #16
    Originally posted by russ View Post
    A chopped DC current then?
    Not just chopped, but sequenced to different windings at different angles around the shaft, just as in a polyphase AC motor.
    Or a chasing sequence Xmas light controller.

    You could think of it as the DC equivalent of a VFD.

    The "three phase" part would just indicate that there are three winding sets at 120 degree angular displacement.
    You could make the motor with two or with 15 depending on what operating characteristics you need.

    I think that the direct drive motors in modern front load washing machines work in the same way but with a very large number of poles compared to the number of phases.
    Last edited by inetdog; 06-04-2014, 09:15 PM.
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

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    • #17
      Originally posted by inetdog View Post
      Not just chopped, but sequenced to different windings at different angles around the shaft, just as in a polyphase AC motor.
      Or a chasing sequence Xmas light controller.

      You could think of it as the DC equivalent of a VFD.

      The "three phase" part would just indicate that there are three winding sets at 120 degree angular displacement.
      Thanks - I was curious what it meant and now I know
      [SIGPIC][/SIGPIC]

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      • #18
        Originally posted by russ View Post
        Thanks - I was curious what it meant and now I know
        You are welcome Russ.
        A very common place to find this kind of motor these days is in the traction motors of electric or hybrid vehicles where controlability and efficiency are at a premium.
        SunnyBoy 3000 US, 18 BP Solar 175B panels.

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        • #19
          I thought the controllers (from sun pump et al) converted the DC into PWM AC? I know you can put a clamp on AC meter on the wires from the controller and measure amps on the sun pump, which you normally cannot do on a DC circuit.

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          • #20
            Originally posted by Texas Wellman View Post
            I thought the controllers (from sun pump et al) converted the DC into PWM AC? I know you can put a clamp on AC meter on the wires from the controller and measure amps on the sun pump, which you normally cannot do on a DC circuit.
            Some pump controllers convert DC to PWM AC with an approximately sinusoidal waveform and potentially multiple phases. This is required when the motor in question is an AC induction motor.
            If instead the motor is a brushless DC motor, then it requires controlled (usually by PWM) DC applied to the various windings at the right times while the field is provided by permanent magnets or by a DC field coil.
            But even then, part way through the rotation the controller will be applying a negative DC voltage to the same coils that it applied a positive voltage to earlier in the cycle. That means that an AC ammeter will read AC amps.
            SunnyBoy 3000 US, 18 BP Solar 175B panels.

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            • #21
              Solar pumps options

              I sell solar gear and solar pumps, to size the pump that you would need this is what i would need to know:
              elevation (from water source to destination)
              distance (from water source to destination)
              Pipe size if existing
              flow rate required (i can work this out for you if you know your tank/dam size and how long it takes you or your stock to empty it in in the peak of summer)

              [B]Mod note - no advertising please.[/B]
              Last edited by russ; 09-24-2014, 01:26 AM.

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              • #22
                More pumping questions

                I am looking to pump from a sump to a pond and am getting close to ordering equipment. 2hp 3-phase goulds we 20h submersible low head pump 230vac. I project the pump capacity to be about 121gpm against about 40' total dynamic head. I have found some information indicating that a variable frequency drive can be made to run directly off of panels if they are linked in series to provide the drive's dc bus voltage. See schnieder altivar drives. Does anyone here have experience with this type of system? It sounds like it might work well for OP's situation, and vfds are very flexible when it comes to programming pump speeds with different kinds of inputs.

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