VFD and small pump

[ptonsparky]

Customer supplied a 1 hp 3 ph centrifugal pump for dust suppression (add oil of some sort) in a dusty process. I do not know the model #. Viking pump direct drive.
For whatever reason the 1/4 hp was deemed no longer adequate. Don?t know why.

They also wanted a VFD on the pump to reduce flow. Ok. They had a 5 hp drive I suggested they use. Never dreamt the overload would not go low enough for the 1 hp. Yes I know, READ the directions.

System ran until I got the smaller drive. Now that I can dial in the proper over load it trips. OL1. MVX 9000. Current display indicates .9 amps, FLA is supposed to be set at 1.5 but it will not stay running under 1.9. I did not put my own meter on it.

The pump is oversized and they run it at 9hz. My thought is that the pump is running to slow and actually causing the motor current to surge a bit has it tries to maintain HZ. While the current display remains steady the drive is taking the actual current into account and tripping on overload.

I am pretty sure the piping size and location of the pump are not as suggested by the installation Manual and may add to the problem.

Thoughts or suggested corrections welcome.

 

[milldrone]

System ran until I got the smaller drive. Now that I can dial in the proper over load it trips. OL1. MVX 9000. Current display indicates .9 amps, FLA is supposed to be set at 1.5 but it will not stay running under 1.9. I did not put my own meter on it.

The pump is oversized and they run it at 9hz.

Are you sure this is a centrifugal pump? I'm having a hard time believing you are developing useful pressure at 9 Hz.

If it is a centrifugal. have you tried the voltage boost settings? You will need to be in V/Hz mode and not sensorless vector. I believe this is your parameter 50.10 (minimum voltage) Experiment with small changes and be prepared to change it back to where you found it. The low end voltage boost settings do not always work like you want them to!

 

[Cow]

Customer supplied a 1 hp 3 ph centrifugal pump for dust suppression (add oil of some sort) in a dusty process. I do not know the model #. Viking pump direct drive.
For whatever reason the 1/4 hp was deemed no longer adequate. Don’t know why.

They also wanted a VFD on the pump to reduce flow. Ok. They had a 5 hp drive I suggested they use. Never dreamt the overload would not go low enough for the 1 hp. Yes I know, READ the directions.

System ran until I got the smaller drive. Now that I can dial in the proper over load it trips. OL1. MVX 9000. Current display indicates .9 amps, FLA is supposed to be set at 1.5 but it will not stay running under 1.9. I did not put my own meter on it.

The pump is oversized and they run it at 9hz. My thought is that the pump is running to slow and actually causing the motor current to surge a bit has it tries to maintain HZ. While the current display remains steady the drive is taking the actual current into account and tripping on overload.

I am pretty sure the piping size and location of the pump are not as suggested by the installation Manual and may add to the problem.

Thoughts or suggested corrections welcome.

BINGO!

I'd tell them to get the proper size pump. Then when they give your grief about buying another pump, like all the farmers I work for would do, I'd end up calling the pump manufacturer myself and have them tell the farmer the same thing!

Similar story, my last trainwreck was an auger for a manure seperator. The farmer wanted to speed it up, he found out a gearbox vs. a vfd were about the same price. So, instead of ordering the gearbox, he picked the VFD(Don't ask me why??) and then wanted it cranked up to 80 hz. Well, like you can imagine, it tripped. And tripped. And tripped. After one or two visits of checking and resetting the drive along with the swearing to go along with it, it's back down to about 70 hz. Right on the ragged edge of tripping the overloads. He would of been money ahead to change the gearbox. Sometimes customers just don't get it, no matter what you tell them!

 

[ptonsparky]

Centrifical is not right. More on the rotary positive displacement.

I've tried both settings and even went thru the autotune, option 2, I believe.

Owners are a thousand miles away & I have to bid everything. Hate to leave it this way but I can't spend a lot of time on it either.

 

[hurk27]

How is the motor cooled? running a non-inverter rated motor to slow can cause the motor to over heat, most inverter rated motors have large fins to dissipate the heat, non-inverter rated motors have fans, spin them to slow and you wind up with a burnt up motor.

 

[iwire]

He would of been money ahead to change the gearbox.

No reason to think that would not have also caused tripping as well.

 

[don_resqcapt19]

... Right on the ragged edge of tripping the overloads. He would of been money ahead to change the gearbox. Sometimes customers just don't get it, no matter what you tell them!

He would have had the same tripping issue with the motor overloads if he used the gear box to increase the speed.

 

[ptonsparky]

How is the motor cooled? running a non-inverter rated motor to slow can cause the motor to over heat, most inverter rated motors have large fins to dissipate the heat, non-inverter rated motors have fans, spin them to slow and you wind up with a burnt up motor.

Motor nameplate indicates a 4 pole with base frequency of 60 HZ . Max RPM of 5400. I did not see inverter duty stated on the namplate (bifocals and dark corner) but would take a semieducated guess that it is. Maybe the large fins played into that decision as well. They had been warned about the slow rpm and in the two weeks prior to the new drive they checked it with no sense of it being hot.

 

[kwired]

I don't see why a larger than necessary motor would cause overload problems. If anything the motor needs oversized for improved cooling.

I think there is a good chance of a wrong parameter someplace in the programming of the vfd that is giving the wrong voltage to frequency ratio or something along that line.

Unlike a centrifigual pump a positive pump will still require a high amount of troque at a low speed.

What is nature of product being pumped? If you are trying to pump it to a high pressure you definately will have a high current even at a low speed. If it is a really thick liquid it will also draw high current even at low speed. The amount of torque needed may be the reason and not necessarily the speed of the pump.

 

[weressl]

Customer supplied a 1 hp 3 ph centrifugal pump for dust suppression (add oil of some sort) in a dusty process. I do not know the model #. Viking pump direct drive.
For whatever reason the 1/4 hp was deemed no longer adequate. Don?t know why.

They also wanted a VFD on the pump to reduce flow. Ok. They had a 5 hp drive I suggested they use. Never dreamt the overload would not go low enough for the 1 hp. Yes I know, READ the directions.

System ran until I got the smaller drive. Now that I can dial in the proper over load it trips. OL1. MVX 9000. Current display indicates .9 amps, FLA is supposed to be set at 1.5 but it will not stay running under 1.9. I did not put my own meter on it.

The pump is oversized and they run it at 9hz. My thought is that the pump is running to slow and actually causing the motor current to surge a bit has it tries to maintain HZ. While the current display remains steady the drive is taking the actual current into account and tripping on overload.

I am pretty sure the piping size and location of the pump are not as suggested by the installation Manual and may add to the problem.

Thoughts or suggested corrections welcome.

Viking does not make centrifugal pumps. All their equipment is positive displacement pump, which seems appropriate for a de-dusting oil spray application.
You are dealing with a constant torque application which means that at 9Hz it requires the same torque as at full speed. Check the torque related settings. Usually the recommended turndown for constant torque aplication is 1:6, so at 9Hz you are below that range. In the case of variable torque the canned answer from the manufacturer is: use next largest size if it doesn't work.(That answer always puzzled me. Will they take back the dirve what I just purchased for full credit? Kind of doubt it....)

Your problem may be further compounded by the fact that you identify the speed as 5400rpm max. Ordinary assynchronous motors would have a max speed of <3600rpm @ 60Hz and unless you specified the output frequency at greater than 60Hz, your drive would not operate properly.

I am missing what size drive are you using now.

I would put the 5HP drive back, check all the parameters, boost the torque and see what happens.

"They" say that the current pump and motor size is appropriate, but that could also be a problem.

 

[Jraef]

A couple possibilities I can think of:

1. The Torque Boost setting as mentioned by milldrone, but for the OPPOSITE reasons. In some cases VFDs have the torque boost turned on as the default, usually at 10Hz and below. What that does is to increase the voltage (within the V/Hz ratio) at those lower speeds in order to TEMPORARILY increase torque, ASSuming you are just starting out and need to overcome friction. But you cannot run that way permanently as it saturates the windings; it's meant to be a band that you pass through. So if you are going to run at that speed all the time, you may need to make sure Torque Boost is turned off.
2. Many VFDs have a feature in their overload protection algorithm that ASSumes that the motor will not properly cool itself below a specific speed. There is something called the Motor Cooling Constant that is normally used to compensate for cold or hot starting. But in VFD protection, some mfrs now tweak it to account for the reduced cooling effects found in non-inverter duty motors. That's why in some VFD setup routines it will ask you if it is an inverter duty motor or not, and if it has a separate cooling fan etc. etc. If you have a non-inverter duty motor and no external cooling fan, it may be assuming the worst and dialing DOWN the OL pprotection algorithm knowing that the motor can't take it.
   
   However I'm a little confused in this case. You implied your motor current appears to be 1.9A. If the FLA is stated as 1.5A and the motor is pulling 1.9A, that is 26.6% high, the classic definition of an overload. But then you said the VFD display reads 0.9A, so where did the 1.9A come from? If by that you meant that the motor is drawing 0.9A but you have to manually set the OL protection to 1.9A in order to allow it to run, that may indicate what I said above; the algorithm is getting tweaked because of the low speed. You may need to dig into the motor OL protection scheme a little deeper.

 

[ptonsparky]

Viking does not make centrifugal pumps. All their equipment is positive displacement pump, which seems appropriate for a de-dusting oil spray application.
You are dealing with a constant torque application which means that at 9Hz it requires the same torque as at full speed. Check the torque related settings. Usually the recommended turndown for constant torque aplication is 1:6, so at 9Hz you are below that range. In the case of variable torque the canned answer from the manufacturer is: use next largest size if it doesn't work.(That answer always puzzled me. Will they take back the dirve what I just purchased for full credit? Kind of doubt it....)

Your problem may be further compounded by the fact that you identify the speed as 5400rpm max. Ordinary assynchronous motors would have a max speed of <3600rpm @ 60Hz and unless you specified the output frequency at greater than 60Hz, your drive would not operate properly.

I am missing what size drive are you using now.

I would put the 5HP drive back, check all the parameters, boost the torque and see what happens.

"They" say that the current pump and motor size is appropriate, but that could also be a problem.

You are correct the pumps are positive displacement with constant torque application. Viking just told me they size their drives @ twice the motor hp. Great.

I am using a 1hp drive rated at 3 amps. Motor FLA is 1.5.

My help installed the previous 5hp drive. The only problem we had with that, to my knowledge is the ovld selection would not go down far enough. Min is 30% of its 8.2A.


I see Jraef left a reply but for some reason it doesn't show up. ??

 

[ptonsparky]

now i see it.

 

[ptonsparky]

Yes, the display indicates a current of .9 amps. It will not run at a 1.7 amp setting. I skipped 1.8 and set the overload protection at 1.9.

Dealing with the Max 5400 rpm would, as I see it, indicate that my drive could be set to a max of 180HZ. Would that change the way the motor is trying to supply torque at the 9 HZ ?

 

[ptonsparky]

:slapheadarmaeter 70 - Protective :ashamed1:

It was to easy. Parameter 70.07 electronic thermal overload relay Make it inactive. setting 02.

 

[weressl]

:slapheadarmaeter 70 - Protective :ashamed1:

It was to easy. Parameter 70.07 electronic thermal overload relay Make it inactive. setting 02.

Yeah, burn baby, burn.....:happysad:

 

[ptonsparky]

Yeah, burn baby, burn.....:happysad:

Possibly. Tech support recommendation. I would have chose the constant torque setting first but he did not think it would help.

 

[Jraef]

Yes, the display indicates a current of .9 amps. It will not run at a 1.7 amp setting. I skipped 1.8 and set the overload protection at 1.9.

Dealing with the Max 5400 rpm would, as I see it, indicate that my drive could be set to a max of 180HZ. Would that change the way the motor is trying to supply torque at the 9 HZ ?

If the motor nameplate said "Maximum speed 5400RPM, all that is saying is that the bearings and balancing are designed to allow you to take the motor to 5400RPM, not that this is the speed it SHOULD be run. That is the decision of the pump designer. A 4 pole 60Hz motor will run 1800RPM minus slip%. If you programmed the motor parameters as 4 pole, the 5400RPM value should be meaningless as far as the VFD is concerned.

Running without overload protection is not meeting code of course, so hopefully you were being factitious.

 

[kwired]

Do you know what current was when running with the 5HP drive?

If it was an acceptable level you may want to look at what differences are in paramaters between that drive and the one you are now using.

I am assuming the original 1/4 hp motor was able to handle the load, and they now want to be able to run it at a reduced speed?

What is current like at a higher speed?

Is there pressure regulation in the pumped material or is there not enough pressure at reduced speed for regulation to work properly?

I recently had a positive pump service call - overload tripping. I kept telling the guy there was too much load, nothing else was wrong. He did not want to believe me - that damn tripping overload is an electrical problem. We finally figured out he had installed the wrong nozzle on the injection port that this is pumping to and was causing excess pressure and load on the pump. Sometimes the load has the problem and not the motor or what is driving the motor.

 

[ptonsparky]

I turned off the feature that would, I believe, calculate and provide thermal protection for the motor based on the load type, current and motor speed. I set actual overcurrent parameter to motor FLA. No one was around so I will check in tomorrow and see how it works out