Cooling tower VFD Min Speed - Page 2
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  1. #14
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    Don't let the Mods see you fighting like this.

    haha play nice..

  2. #15
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    No fighting here. We been buds for along time. Just a "thing" that happened in the past so we will shut this one down and get back to the original post. I became a "thread high jacker" Absrbrtek, don't baned me please! LOL
    "I'm from Texas, what country are you from?"

  3. #16
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    Can I ask a question here? Why not let it go to 0? Why run a motor without purpose. Isn't the most efficient motor, a motor that isn't running? 0 power consumption. It's a soft start, so locked rotor amps isn't a issue. Maybe I'm way off on this one too.

  4. #17
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    Quote Originally Posted by maxpower View Post
    Can I ask a question here? Why not let it go to 0? Why run a motor without purpose. Isn't the most efficient motor, a motor that isn't running? 0 power consumption. It's a soft start, so locked rotor amps isn't a issue. Maybe I'm way off on this one too.
    Even VFD rated motors have minimum speed ratings for the most part. There are multiple issues. Cooling of the windings, lubrication of the bearings, and probably a few others. Yes you could go from 15-20hz straight down cycle off. The invertor electronics probably take some extra heat on each start stop though, so there are trade offs.

  5. #18
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    I came up with some Baldore info that gave a ratio of 20to1 for Emotors and 1000 to 1 for super E motors in a variable torque application. I did not understsnd the ratio or what it meant. The way I see it is it depends on the application were like a cooling tower fan is heavy and takes some torque to get it and keep it moving. If the application has less torque requirement we could slow it down more the more the low speed torque requirement the higher the min speed. ???

    The Baldor specs said something about the motor having full torque all the way down to 0 hz but I watched the amps on a 20 HP motor at 20 amps at a 5HZ output on the drive.
    "Dying aint much, its living thats hard." (Josey Whales)

  6. #19
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    Oh by the way StickerBritches it a belt driven tower.
    "Dying aint much, its living thats hard." (Josey Whales)

  7. #20
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    You probably do not want to go much below 20 Hz for a prolonged period. Motor cooling can become a real issue at speeds lower than that.

  8. #21
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    Quote Originally Posted by Chiller Guy View Post
    You probably do not want to go much below 20 Hz for a prolonged period. Motor cooling can become a real issue at speeds lower than that.
    Why not 0 hz? Screw the engineers. Minimum hz wastes power. Adjust your PID from 0 hz. sorry for that outburst.lol

  9. #22
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    Quote Originally Posted by maxpower View Post
    Why not 0 hz? Screw the engineers. Minimum hz wastes power. Adjust your PID from 0 hz. sorry for that outburst.lol
    You can do that but you have to kill the signal. You don't want to have it operate for extended period of time below 20hz. On a tower, if the load continues to drop, shut it off. He is looking for min speed set up in the drive. That is a settable parameter.
    Ok Capt. Jack, you did not specify it was belt driven. Rookie!
    "I'm from Texas, what country are you from?"

  10. #23
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    Wink cooling tower vfd min. speed

    josey wales said " dying ain`t much of a living boy".

  11. #24
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    "Weighing in at"

    10Hz if it is belt drive & 20Hz if it is a gear box. However, some gearbox mfrs will let you go a little (not much) lower. You may want to give them a call & ask.

    The next thing I like to do on the tower fan applications is to program the drive so that it will cycle off if it runs at min speed for 5 minutes. Some times 10 or somewhere in between. I've also experimented with different on buffers, depending on how fast it would try to cycle back on.
    All my leon freaked out!

  12. #25
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    Quote Originally Posted by turbovac View Post
    josey wales said " dying ain`t much of a living boy".
    Yes he said that also!
    "Dying aint much, its living thats hard." (Josey Whales)

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