VFD issues

[Marvo]

I'd be interested to know what transpires if you can find the time to post again in a few days.

If ABB are prepared to swap out the drive at no cost then it would be wise to do so just to rule out that as a possibility.

If your pump is a multistage centrif then low head is not a place where you want to be, even if the head is slightly below specified minimum it can have a marked detrimental effect on mean time between failures so artificially introducing extra head pressure is a close second best to re-specifying a pump with a lower head requirement.

<1 second to >3450rpm is a steep start ramp, it's steeper than the default ramp settings of most drives so I'd double check these settings which may be critical to ensure bearing hydraulic action and possibly seating of the impellers. Also with bearings that rely on water hydraulics for lubrication I'd avoid dry run at all costs, it could lead to the demise of the pump faster than a marginally high run current.

Maybe consider a 0-10 volt level sensor (or something similar that's drive compatible) that can signal the drive to modulate the motor speed between 30-60HZ, it might be simpler and more reliable than PID operation.

Good luck and I'll look forward to reading what happens.

 

[KAG]

FYI I do have a 4-20ma transducer in the well. 0-15psig. Set at 31ft with a setpoint of 10ft (21 from surface). These are submersible open design impellers. Motor is always submerged and the stack can take a ton of run dry without issue. We once ran a pump and motor out of the water for 75 minutes without damage. I think we got lucky! Anyway it may be a programming issue and although I was given parameters directly by the ABB tech people that doesn't mean it's correct. I'll keep you posted once we iron it all out. This has been one of THOSE projects anyway! Again your help is greatly appreciated.

 

[Engineer54]

Now this has been an interesting thread, and i'm also looking forward to what happens on the OP's end....

 

[i=p/u]

If you don't understand I can talk you through what they on About.....

 

[KAG]

I'm certainly open to any suggestions for alternatives to pid control or perhaps programming suggestions. Feel free to email me and I'll give you the blow by blow. I'm thinking I may have to limit the motor to a level where it stays in the curve. Perhaps 50-55hz.

 

[Marvo]

Can you give more info about the end game you're trying to achieve? You have a pump in a well with a level transducer, is that transducer actually there for level control or is it just dry run safety? Where is the pumped water going and what processes on the discharge side of the pump are you trying to control?

 

[KAG]

Ok. Here we go. We have a basement in a building that floods during rain events. There is a layer of porous sand at a foot below the basement floor that is perched on top of the solid rock. When it rains it fills rapidly and sump pumps can barely keep up to the demand. We drilled a hole just outside the foundation wall to drop the water to a level where we could intercept a large portion of it before it enters the building. We installed a submersible pump inside of a sand packed pvc liner to a depth well below that sand level to force the water out and down. Once we begin pumping we discharge the water to a storm drain prior to entering the facility. Long term the constant pumping will drain the zone and make the rain events less of a catastrophe so ideally this pump will run continuously unless it somehow is completely dewatered. All I really need to do is keep the water level just below that sand layer at all times. here are some details.
Hole depth - 46ft
Diameter 4.25" ID inside sand packed 6" hole
Pump intake at 33ft
Transducer - 4-20 hanging at 31ft
Current draw 7.5 SFA 8.5
2hp 200v 3 phase
ABB ACS310 drive

Basically the discharge water just runs to city storm sewer. The motor went into overload once either as a result of lack of head or some other mechanical factor. Screen slots on the pump are less than 1/8 inch and sand grade outside the liner is 1/8 x 1/4 with .125 mchine slots. No doubt some rogue particles can get through but even if they pass the well screen and enter the pump somehow they should be pumped out without difficulty. Certainly not enough to send a pump running at full speed into overload. I am suspecting lack of head on the submersible may be the culprit.

 

[Tomma23]

Hi Kag & Marvo . Is it so that using PID control for what appears to be just a matter of controlling the Water Head level a bit over complicating the function . Could you not use say a two stage Bilge Level switch giving a High and a High High input to the VFD for 2 fixed speed outputs with suitable ramp up times . Use the lower level of the High switch to stop the Pump and protect from dry running . Just a thought . Regards

 

[Engineer54]

If you don't understand I can talk you through what they on About.....

Now you ARE joking!! no-one can understand your one line posts, let alone you trying to explain issues with a VDF controlled pump motor!! lol!!

 

[KAG]

Looked like plain english to me!

 

[i=p/u]

So that's what is you on about. .... Pittsburgh rocks.

 

[Darkwood]

I had a similar issue although its clear its not your issue after reading through; .... a submersible pump had been repaired by others but next heavy rain fall it tripped O/L ... through investigation it had been connected up with phases swapped and was running backwards now the obvious thought would be it wouldn't pump but it did pump successfully at about 50% flow rate reduction at full speed but with much higher current demand as the natural water flow was fighting rotation.

I doubt this is anything to do with your set up as you say you can run it fine without PID but just putting it out there as a future ref' it tends to go against the grain and is counter-intuitive.

Another thought though is the Inverter in damp conditions or got any dust contaminants?
Is it set up for reverse lockout so a erroneous input, tracking signal wont give a reverse direction command...?

 

[Engineer54]

Looked like plain english to me!

You need to look at his other posts to see what i mean, or even his last post here #25!! lol!!

 

[Silly Sausage]

Hahaha...I hope he (i=p/u) doesn't talk like this to his clients/bosses!!! :smilielol5::smilielol5:

 

[Knobhead]

I’m trying to get my head around why you need a VSD on a sump pump? Basic level control of a DOL starter makes more sense to me.
Can you post a link to the pump manufacturer and the type?