Large Well Pump on VFD

[adamscb]

Forum,

I'll be required to program a VFD that is connected to a vertical 300hp well pump here in the near future - my quick question is that will this be any different from programming a VFD for a small motor? Do I need to take any extra considerations (i.e. torque, ramp speed, etc.)? The basic settings that I usually program are rated voltage, rated amps, motor horsepower, rpm, service factor, basically anything and everything on the nameplate, and then of course the digital inputs / digital outputs and the analog inputs / analog outputs. If anyone has any experience in this let me know, thanks!

 

[Open Neutral]

How long are the VFD to pump leads?

 

[adamscb]

How long are the VFD to pump leads?

I'd say between 200-250 feet. Line and load reactors were ordered with this VFD.

 

[Cow]

What is giving the VFD it's start/stop/speed commands? Is it maintaining a constant pressure? Do you need a backspin timer?

 

[ptonsparky]

The software that goes with the drives is worth the effort. Some are free and use common cables. Others, well, see if the rep will at least give you a hug for the money.

Dont be bashful about using the support. You paid for it and they want it to work.

 

[Jraef]

One suggestion learned the hard way. Despite how fast someone WANTS to accelerate it, don't. I have had the pump suck in the well casing from being too aggressive. There may be a minimum accel time to get to a speed at which the pump rises off of a thrust bearing, the pump supplier should be able to tell you that. But until you know more about how the pump and well react to each other, take it low and slow.

 

[ptonsparky]

One suggestion learned the hard way. Despite how fast someone WANTS to accelerate it, don't. I have had the pump suck in the well casing from being too aggressive. There may be a minimum accel time to get to a speed at which the pump rises off of a thrust bearing, the pump supplier should be able to tell you that. But until you know more about how the pump and well react to each other, take it low and slow.

I'd say between 200-250 feet. Line and load reactors were ordered with this VFD.

Is this a submersible pump motor or above ground? We call them hollow shaft motors.

 

[GoldDigger]

Jraef, do you mean a maximum time to get to lift off speed, not minimum?

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[adamscb]

What is giving the VFD it's start/stop/speed commands? Is it maintaining a constant pressure? Do you need a backspin timer?

The local start/stop and a start/stop command from the PLC is controlling whether to turn on or off. The head project engineer is planning on varying the frequency using a PID loop. Not sure if we have a backspin timer on this already or not.

Is this a submersible pump motor or above ground? We call them hollow shaft motors.

This well motor is above ground.

One suggestion learned the hard way. Despite how fast someone WANTS to accelerate it, don't. I have had the pump suck in the well casing from being too aggressive. There may be a minimum accel time to get to a speed at which the pump rises off of a thrust bearing, the pump supplier should be able to tell you that. But until you know more about how the pump and well react to each other, take it low and slow.

Now that I think about this more, this well pump currently starts across-the-line, so I don't think acceleration time will be an issue (at least I wouldn't think so).

 

[ptonsparky]

Jraef, do you mean a maximum time to get to lift off speed, not minimum?

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Franklin pumps used to want .5 second to reach half speed for their submersibles, granted those are house or stock wells. So is that maximum or minimum time?:blink:

 

[GoldDigger]

There is a minimum rotational speed at which a fluid dynamic bearing lifts off. Too many rotations below that speed causes excessive wear.
But that is probably less than half speed.
If Franklin gives only one specified speed point I would have to treat it as both min and Max.

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[Dzboyce]

Almost all submersible pump motors have a kingsbury type thrust bearing. The motor needs to rotate at least 1800 rpm to properly lubricate the bearing. Doesn't matter if it's a 1/2 horsepower or a 200 hp motor. All the submersible manufacturers I'm aware of, require that the motor accelerate to a minimum speed of 30 hz within 1/2 second. After reaching 30 hz acceleration can be at any speed. Most centrifugal pumps don't really do anything until they get above 40 hz. It's very common to program 40 hz as the minimum speed. It's also very common to program in a "pipe fill mode" at at 45-50 hz or so.

A very common programming is
1. 30 hz with in 0.5 seconds, then
2. 45 hz until 15 psi is reached, then
3. PID to maintain a preset pressure at whatever hz is required., then
4. If motor runs at minimum speed of 40 hz for X amount of time with no change in preset pressure., then
5. Motor coasts to stop, drive goes into sleep mode until pressure drops to preset start pressure, then back to 1, skipping step 2.

hollow lineshaft turbine motors don't have the 30 hz minimum speed, because they have conventional ball or tapered roller thrust bearings.

a slow acceleration and deceleration of the motor helps to prevent water hammer.

Earlier this summer, I installed a 100 hp submersible in a well. The irrigation dealer that installed the center pivot installed a Yaskawa drive for the pump. It is programmed with a 10 minute long pipe fill mode to fill up the main line and pivot pipe before the changing to PID control at 40 psi.

 

[Jraef]

Jraef, do you mean a maximum time to get to lift off speed, not minimum?

Sent from my XT1585 using Tapatalk

Yes. I said that backward. :slaphead:
I even thought about it twice, still got it wrong. I was sitting at a trade show booth bored out of my gourd, but just as I typed that, someone asked me a really dumb question and I lost concentration.

 

[Besoeker]

My two pence worth.......or two cents if you want.......
From my very limited experience...
Pumps are usually low inertia compared to the drive motor. Unless, for process reasons, acceleration time should not be too critical.
Speed range may be worth considering. Centrifugal pumps don't do a lot below 70% of rated speed.

Mechanical resonances may need to be considered. At 300HP you have two inertias at either end of a shaft and thus the potential for resonance at certain frequencies. Probably not your bag to determine that but you may have to programme in skip frequencies to avoid resonances.

 

[RumRunner]

My two pence worth.......or two cents if you want.......
From my very limited experience...
Pumps are usually low inertia compared to the drive motor. Unless, for process reasons, acceleration time should not be too critical.
Speed range may be worth considering. Centrifugal pumps don't do a lot below 70% of rated speed.

Mechanical resonances may need to be considered. At 300HP you have two inertias at either end of a shaft and thus the potential for resonance at certain frequencies. Probably not your bag to determine that but you may have to programme in skip frequencies to avoid resonances.

OP indicated that this pump is above ground. Centrifugal pumps don't do well in pulling liquid. . . they do well in in pushing as in the case of submersible pumps.

I think OP is reading too much about VFD and its purported blessings promoted by VFD manufacturer.

Granted, VFDs are exceptional in some applications like moving air, precise speed control in transportation and other mfg processes . . . not in pumping liquid.

Positive displacement and sometimes called jet pumps vs centrifugal pumps are critical in maintaining head pressure to accomplish the task like pressure washers, irrigation, sewage and lift stations.

I had been involved in early development of VFDs in the seventies after its first inception in Finland in the sixties.

Their popularity were exploited by US mfg like Emerson and others. They are are not exactly what they are cracked up to be in all applications.

You might want to check this out:

http://www.cyclestopvalves.com/vfd-energy_15.html

 

[Besoeker]

OP indicated that this pump is above ground.

The motor, not the pump.

 

[ptonsparky]

Local POCOs here now require soft starts or VFD on motors over 100 HP, so whatever you feel about VFD cost effectiveness is moot.

 

[Jraef]

OP indicated that this pump is above ground. Centrifugal pumps don't do well in pulling liquid. . . they do well in in pushing as in the case of submersible pumps.

I think OP is reading too much about VFD and its purported blessings promoted by VFD manufacturer.

Granted, VFDs are exceptional in some applications like moving air, precise speed control in transportation and other mfg processes . . . not in pumping liquid.

Positive displacement and sometimes called jet pumps vs centrifugal pumps are critical in maintaining head pressure to accomplish the task like pressure washers, irrigation, sewage and lift stations.

I had been involved in early development of VFDs in the seventies after its first inception in Finland in the sixties.

Their popularity were exploited by US mfg like Emerson and others. They are are not exactly what they are cracked up to be in all applications.

You might want to check this out:

http://www.cyclestopvalves.com/vfd-energy_15.html

Well, them new fangled auto-mobiles are just a fad too, sooner or later everyone will go back to horses, you'll see...

In seriousness though, yes, a lot of people over the years have "over sold" the concept of VFDs for sure and most of those people have fallen by the wayside now because lies have a way of catching up to you. But your outright condemnation of them flies in the face of hundreds of thousands of very very successful applications over the past 20-odd years that have highly documented and substantial energy savings over throttling valve applications when used on centrifugal pumps.

The OP was not asking for advice on whether to use a VFD or not anyway, someone already made that decision. He was asking for advice on connecting and programming it.

 

[Besoeker]

OP indicated that this pump is above ground. Centrifugal pumps don't do well in pulling liquid. . . they do well in in pushing as in the case of submersible pumps.

I think OP is reading too much about VFD and its purported blessings promoted by VFD manufacturer.

Granted, VFDs are exceptional in some applications like moving air, precise speed control in transportation and other mfg processes . . . not in pumping liquid.

Positive displacement and sometimes called jet pumps vs centrifugal pumps are critical in maintaining head pressure to accomplish the task like pressure washers, irrigation, sewage and lift stations.

I had been involved in early development of VFDs in the seventies after its first inception in Finland in the sixties.

Their popularity were exploited by US mfg like Emerson and others. They are are not exactly what they are cracked up to be in all applications.

You might want to check this out:

http://www.cyclestopvalves.com/vfd-energy_15.html

This is just utter nonsense..........

"These Variable Speed type pumps do not save energy"

 

[adamscb]

Well, them new fangled auto-mobiles are just a fad too, sooner or later everyone will go back to horses, you'll see...

In seriousness though, yes, a lot of people over the years have "over sold" the concept of VFDs for sure and most of those people have fallen by the wayside now because lies have a way of catching up to you. But your outright condemnation of them flies in the face of hundreds of thousands of very very successful applications over the past 20-odd years that have highly documented and substantial energy savings over throttling valve applications when used on centrifugal pumps.

The OP was not asking for advice on whether to use a VFD or not anyway, someone already made that decision. He was asking for advice on connecting and programming it.

Exactly what Jraef is saying. I'm not the project engineer in this scenario, I just spec out and program the drive