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Thread: Vertical 300hp Well Pump Motor

  1. #11
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    Quote Originally Posted by Ingenieur View Post
    we used vfd's, to limit inrush current, but the sewage pumps always ran at full speed
    they were not much more expensive than a SS, but offered more flexibility
    our utility REQUIRED anything over 25 HP to have a vfd (or SS), even for constant speed application

    best to include the whole post rather than selectively edit and highlight to demean someone
    Ingenieur
    is the pumping rate constant? head and gpm?
    is the drive modulated or running at a constant speed once started?
    The question was CT or VT. That has been answered.
    Spare the irrelevant clutter. OK?
    Si hoc legere scis nimium eruditionis habes.

  2. #12
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    You should coordinate this with pump motor mfr and drive mfr. A lot of special requirements for deep submersibles with VFD. Notably ramp up/down times for porpoer cooling and OL protection.

    femyers.com/~/media/websites/myers/sellsheets/48150.pdf

  3. #13
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    Quote Originally Posted by Ingenieur View Post
    the requirement applied if you took service at 480 vac or less (which we always did for remote pumping sites)
    you probably take it much higher

    you app is variable torque then
    but honestly, iffy, say if you change the speed once a year, then fixed for long periods, versus a controller constant varying speed under changing head conditions
    either way, safe with variable torque
    Our service is 69kV. We're using a PID loop to constantly vary the speed under changing head pressure conditions.

  4. #14
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    Quote Originally Posted by smoothops10 View Post
    You should coordinate this with pump motor mfr and drive mfr. A lot of special requirements for deep submersibles with VFD. Notably ramp up/down times for porpoer cooling and OL protection.

    femyers.com/~/media/websites/myers/sellsheets/48150.pdf
    Yes, but that would probably be of more significance for the motor.

    A little tale. And something the OP ought to be aware of. I was called to a site where the motors on submersible pumps with VFDs were failing at the rate of about one a month. To keep it brief, the cause was excessive dv/dt. Rate of change of voltage. Over 3000V/us in some cases. A killer if not taken care of at the project design phase.

    Output chokes was the fix. Not all VSD come with them.
    Si hoc legere scis nimium eruditionis habes.

  5. #15
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    Quote Originally Posted by Besoeker View Post
    Yes, but that would probably be of more significance for the motor.

    A little tale. And something the OP ought to be aware of. I was called to a site where the motors on submersible pumps with VFDs were failing at the rate of about one a month. To keep it brief, the cause was excessive dv/dt. Rate of change of voltage. Over 3000V/us in some cases. A killer if not taken care of at the project design phase.

    Output chokes was the fix. Not all VSD come with them.
    I've taken note and installed both line and load reactors. I guess my question then is what control method would be best for this application, since we're varying speed based on plant header PSI, V/Hz or open loop? Since it's varying torque you'd think open loop right? From my understanding V/Hz is for constant torque applications.

  6. #16
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    Quote Originally Posted by adamscb View Post
    I've taken note and installed both line and load reactors. I guess my question then is what control method would be best for this application, since we're varying speed based on plant header PSI, V/Hz or open loop? Since it's varying torque you'd think open loop right? From my understanding V/Hz is for constant torque applications.
    Constant v/f is the way I would go. Reducing the v/f ought to reduce losses. I tried that on some 630kW pump drives. Test results were inconclusive and introduced other problems so we reverted to constant v/f open loop.

    Speed control was from an external 4-20mA loop. We also did the PLC which generated that. But that's another story for another day.
    Si hoc legere scis nimium eruditionis habes.

  7. #17
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    Quote Originally Posted by Besoeker View Post
    The question was CT or VT. That has been answered.
    Spare the irrelevant clutter. OK?
    one mans clutter is another's knowledge
    engineers prefer to know WHY



  8. #18
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    Quote Originally Posted by adamscb View Post
    I've taken note and installed both line and load reactors. I guess my question then is what control method would be best for this application, since we're varying speed based on plant header PSI, V/Hz or open loop? Since it's varying torque you'd think open loop right? From my understanding V/Hz is for constant torque applications.
    v/f since you do not need low f high torque capability
    since you have closed loop PID control the drift will not be an issue


    we use open loop vector for tensioning winch applications
    when you need max torque at <0.3 Hz
    the motor is essentially stationary ~ +/- a few tenths Hz



  9. #19
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    Quote Originally Posted by Ingenieur View Post
    v/f since you do not need low f high torque capability
    since you have closed loop PID control the drift will not be an issue


    we use open loop vector for tensioning winch applications
    when you need max torque at <0.3 Hz
    the motor is essentially stationary ~ +/- a few tenths Hz
    One thing I do want to point out, is that the PID loop isn't set up inside the VFD, but rather in our PLC.

  10. #20
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    Quote Originally Posted by adamscb View Post
    One thing I do want to point out, is that the PID loop isn't set up inside the VFD, but rather in our PLC.
    Yes. And that's how we usually arranged it - a number of drives and one common controller.
    Si hoc legere scis nimium eruditionis habes.

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