VFD issues

[Silly Sausage]

Phew, it's not just me then Tony!
A pump with some level sensors for control and alarm conditions...surely?!?!

 

[Knobhead]

Makes sense to me.

Of the 100’s of pumps I’ve worked on only two had VSD’s, they nearly always ran at about 90/95%. Look at the flow and speed graphs they aren’t linear. Under speed they are inefficient, over speed and they suffer with turbulence.

Crazy setup!

 

[Marvo]

All I really need to do is keep the water level just below that sand layer at all times.

Tony, I assume the PID control is either because he's trying to maintain a level rather than have the pump cycle on/off as it would with a traditional 3-probe liquid level controller. Possible it's also because there a massive difference in pump performance required depending whether it's raining or not. If the pump is sized to deal with the maximum likely rainfall then it will almost certainly 'short-cycle' when it's not raining and probably exceed the maximum number of starts-per-hour specified by the manufacturer.

You can often get away with having an increased number of starts per hour just by using a drive with a ramped start rather than a DOL starter but with a multi-stage centrif pump it needs to start on a steep ramp so you won't get away with more than maybe 10-20% over the manufacturers limit.

I'm also a big fan of simple and PID control can often be anything but simple. It might be possible to use the existing level transducer and have the drive handle it as a proportional only analogue input but without seeing the volume requirement figures it's difficult to say.

 

[KAG]

Marvo you are exactly correct. This is a dewatering application where the level must never rise above a preset depth. In this case the contractor poorly constructed the elevator pit in a commercial building so when a rain event happens it floods. By keeping the water below the elevator pit the problem goes away! We have done many of these but in most case the water production rates remain constant. In this case the volume of production at the soil bedrock interface varies from 10 - 70gpm depending on weather and time of year. To all reading this it is not a sump pump but a high volume submersible turbine. Very similar to you typical water well except larger diameter and greater volume. The idea is to create a cone of depression and essentially dewater the zone so the rain events have as little impact as possible.
Now for the solution. It appears that the folks at ABB called out some settings that were not so compatible with the type of motors used in submersible pumps. After a call to the motor and pump manufacturers we were able to set the gain, integral, ramp up, and carrier frequency to make the pump and motor happy. The current draw is now under service factor and the unit is operating as designed. It appears you were correct (Marvo) that the readings shown by the drive were in fact correct and once the parameters we correctly set we're off and running.
Again I appreciate the help!

 

[Marvo]

Thanks for the explanation, I am familiar with the dewatering technique you've employed and I'm glad to hear you got your settings issue cleared up. Thanks also for coming back and tying the thread up neatly.

 

[Darkwood]

Cheers for the feedback...
Now to implement a second pump and they can run alternately and if and when a trip or pump failure occurs the controls put the remaining pump in charge and alarm up for maintenance well this was my last set-up but it was for chemical waste and keeping it from flooding into the local river so may be overkill in your set up...?

 

[KAG]

Certainly in all cases when you can convince the facility owner to implement a spare anything it's good practice. Economics being what they are today they opted for a high level alarm!

 

[Darkwood]

Certainly in all cases when you can convince the facility owner to implement a spare anything it's good practice. Economics being what they are today they opted for a high level alarm!

and a mop and bucket

 

[Knobhead]

Best laugh I’ve had on here for a long time!

Thanks DW!